• TABLE OF CONTENTS
HIDE
 Front Cover
 Abstracts of papers presented at...
 Interrelationship of radopholus...
 Damping-off disease of tobacco...
 Wilt disease of coconut in socorro,...
 Simultaneous and sequential transmission...
 Economic hosts of pseudomonas solanacearum...
 Effects of five nematicides on...
 Sorghum grain molds: Identification,...
 Sweet potato sucrose agar- An inexpensive...
 Comparative studies on the diplodia-like...
 Microbiology of high-moisture corn...
 Tetep: A potential source of resistance...














Title: Journal of Tropical Plant Pathology
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Title: Journal of Tropical Plant Pathology
Series Title: Journal of Tropical Plant Pathology
Physical Description: Serial
Language: English
Publisher: Philippine Phytopathological Society
Place of Publication: Philippines
Publication Date: 1982
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Bibliographic ID: UF00090520
Volume ID: VID00005
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Resource Identifier: oclc - 1624346
electronic_oclc - 54382605
issn - 0115-0804

Table of Contents
    Front Cover
        Front Cover 1
        Front Cover 2
    Abstracts of papers presented at the nineteenth annual meeting of the Philippine phytopathological society, Pines Hotel, Baguio city, 5-8 May 1982
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    Interrelationship of radopholus simiis and meloidogyne incognita in banana
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    Damping-off disease of tobacco occurrence distribution, and screening for resistance
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    Wilt disease of coconut in socorro, oriental mindoro: I. Survey (1977-1981)
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    Simultaneous and sequential transmission of abaca-mossaic and banana-mosaic viruses to abaca
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    Economic hosts of pseudomonas solanacearum EFS isolates from abaca
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    Effects of five nematicides on the control of nematodes and yield of tomato
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    Sorghum grain molds: Identification, incidence and pathogenicity
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    Sweet potato sucrose agar- An inexpensive culture medium for fungal growth
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    Comparative studies on the diplodia-like organisms isolated from fruits
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    Microbiology of high-moisture corn treated with a ombination of "cold flow" ammonia and propionic acid
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    Tetep: A potential source of resistance to rice dwarf in Nepal
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Full Text
ISSN 0115-0804



Philippine



Phytopathology



VOLUME 18 JANUARY and JUNE 1982 NUMBERS 1 and 2

CONTENTS

Abstracts of Papers Presented at the Nineteenth Annual Meeting of the
Philippine Phytopathological Society, Pines Hotel, Baguio City,
5-8 May 1982 ............. ...... .................. 1-21

Interrelationship of Radopho/us similis and Meloidogyne incognita in
Banana W. Santor and R. G. Davide ..................... 22-33

Damping-off Disease of Tobacco: Occurrence, Distribution, and Screening
for Resistance P.N. Dipon and R.G. Davide ............... 34-42

Wilt Disease of Coconut in Socorro, Oriental Mindoro: I. Survey (1977-
1981) E.C. Concibido, R.G. Abad and J.G. Nuevas, Jr. .......... 43-47

Simultaneous and Sequential Transmission of Abaca-Mosaic and Banana-
Mosaic Viruses to Abaca (Musa textilis Nee) by Aphis gossypii
Glover M. L. Retuerma ............... ............ 48-55

Economic Hosts of Pseudomonas solanacearum EFS Isolates from Abaca -
A R. Rillo ..................................... .... 56-60

Effects of Five Nematicides on the Control of Nematodes and Yield of
Tomato R. G. Davide and R. A. Zorilla ............ ..... .. 61-67

Sorghum Grain Molds: Identification, Incidence and Pathogenicity Maria
P. Dayan and S.C. Dalmacio ................ ............ 68-77

Sweet Potato Sucrose Agar An Inexpensive Culture Medium for Fungal
Growth Lina L. Ilag, Araceli R. Pua and Victoria A. Marfil ....... 78-88

Comparative Studies on the Diplodia- like Orgaisms Isolated from Fruits -
Tricita H. Quimio and Yolanda Dela Cruz .................. 89-101

Microbiology of High-Moisture Corn Treated with a Combination of "Cold
Flow" Ammonia and Propionic acid Ida F. Dalmacio, D. Y. C.
Fung and J. H. MacNeil ..................... ............. 102-107

Tetep: A Potential Source of Resistance to Rice Dwarf in Nepal B. P.
Upadhyay and D. 3. Lapis ................................ 108-113

Official Organ of
THE PHILIPPINE PHYTOPATHOLOGICAL SOCIETY, INC.










PHILIPPINE PHYTOPATHOLOGY
Official Organ of the Philippine Phytopathological Society, Inc.


BOARD OF DIRECTORS 1982-83


FAUSTINO L. NUQUE
VALENTINO G. BALAOING
LINA C. LAPITAN
FRANCISCO A. ELAZEGUI
AVELINO D. RAYMUNDO
LINA L. ILAG
CEFERINO A. BANIQUED
ROMULO G. DAVIDE
PONCIANO M. HALOS
DELFIN B. LAPIS
TRICITA H. QUIMIO
TIBURCIO T. REYES


" President
" Vice-President
* Secretary
* Treasurer
* Auditor
* Ex-Officio
* Board Member
* Board Member
* Board Member
* Board Member
* Board Member
* Board Member


EDITORIAL BOARD


SAMUEL C. DALMACIO
DANTE A. BENIGNO
ROMULO G. DAVIDE
GIL G. DIVINAGRACIA
PONCIANO M. HALOS
LINA L. ILAG
AGUSTIN N. PORDESIMO
TRICITA H. QUIMIO
SEBASTIAN S. QUINIONES
AVELINO D. RAYMUNDO
CEFERINO A. BANIGUED


Editor-in-Chief and Associate Editor for
Associate Editor for Virology
Associate Editor for Nematology
Associate Editor for Pathogenesis
Associate Editor for Bacteriology
Associate Editor Post-Harvest Pathology
Associate Editor for Disease Control
Associate Editor for Mycology
Associate Editor for Forest Pathology
Associate Editor for Epidemiology
Business Manager


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Subscriptions: Communications should be addressed to the TREASURER, P. P. S. c/o Depart-
ment of Plant Pathology, UPLB, College, Laguna 3720. Philippine Phytopathology, published annually,
is the official organ of the Philippine Phytopathological Society, Inc. It is sent free to members in
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Phytopathological Society, Inc.


Disease Resistance












ABSTRACTS OF PAPERS PRESENTED AT THE NINETEENTH
ANNUAL MEETING OF THE PHILIPPINE PHYTOPATHOLOGICAL
SOCIETY, PINES HOTEL, BAGUIO CITY, 5-8 MAY 1982


Fungicidal sprays for banana fruit spot
control. M. O. San Juan (TRRC)

The black pitting disease or Johnson
fruit spot caused by Piricularia grisea and
the diamond spot caused by Fusarium
roseum are the most common blemishes
on the exportable Cavendish banana.
Both diseases become sporadic during the
rainy months of the year. A combination
of phytosanitary measures and bunch
protection can control the diseases.
Several fungicides which were tried in
two separate plantations in Davao have
shown that Dithane M-45, Benlate 50
WP and Topsin Methyl 70 WP were ef-
fective. The dosages used were 30 and
45 g for Benlate 50 WP, 50 and 70 g for
Topsin Methyl 70 WP and 2.4 kg of
Dithane M-45 in 100 liters each of solu-
tion. For each of the above solutions 160
ml Basudin 60 EC and 30 ml Triton B
1956 were added. Control bunches were
unsprayed. Results obtained from the dif-
ferent treatments analyzed by Duncan's
Multiple Range Test showed the follow-
ing order of effectivity: Dithane M-45
(2.4 kgs/100 1), Benlate 50 WP (45
g/100 1), Topsin M 70 WP (70 g / 100 1),
Topsin M 70 WP (50 g/100 1), and
Benlate 50 WP (30 g/100 1). Highly sig-
nificant differences were obtained
between fungicide-treated and unsprayed
bunches.

Pathogenic variability of some Helmin-
thosporium oryzae isolates. B. A. Estrada,
F. L. Nuque, A. Obusan and J.P. Crill
(IRRI)

Preliminary tests were conducted to
study the pathogenic variability of 50
isolates of Helminthosporium oryzae
from 8 provinces of the Philippines. Of


this number, 20 isolates were inoculated
to some cultivars from the germplasm col-
lections and elite breeding lines grown in
plastic trays containing fertile soil in the
greenhouse. Each isolate (spore density of
40,000 to 45,000/ml) was separately ino-
culated to the various cultivars four
weeks after seeding. Inoculated plants
were left inside the inoculation chambers
for at least 24 hr.. Thereafter, they were
transferred to the greenhouse benches for
symptom development. Ten days after
inoculation, tests plants were evaluated
for their reaction to the disease. Initial
results indicated marked variation in the
reaction of the test varieties as well as
variation in pathogenicity among the
isolates. Further tests are being
conducted to select a number of varieties
which can be used as a tentative set of
differential varieties for race grouping.

Epidemiological studies of rice tungro
disease in Luzon. K. C. Ling, E. R.
Tiongco, V.M. Aguiero, and Z.M. Flores
(IRRI).

The epidemiology of tungro was
studied in 37 fields in five provinces in
Luzon from 1973 -- 1980. Insect vectors
Nephotettix virescens, N. nigropictus,
and Reccilia dorsalis were collected and
tested for infectivity. Tungro incidence
and plant growth stages were also recor-
ded. The number of tungro vectors, the
proportion of infective vectors, and tung-
ro incidence varied from field to field
and with time. The study showed that
tungro incidence from June to October
in the wet season rice crop was corre-
lated with the number of tungro vectors
and the proportion that transmitted the
disease from May to July.









Philippine Phytopathology


Interrelationship of soil microflora and
root-knot nematode in roots of tomato.
P. S. Mayol (California State College)

Necrosis of galled tomato roots was
first observed 4, 7, and 10 weeks after
the plants were inoculated with 196,000
Meloidogyne incognita and grown in soil
with high, medium and low levels of mi-
croflora, respectively. Necrosis occurred
even though the respective root galling
indices were similar, indicating that
microbial densities of a soil, rather than
degree of galling have a direct influence
on the incidence and severity of root-
knot infection. Only the dry foliage
weights of plants grown in soil with high
microflora levels and inoculated with
nematodes was significantly reduced
(p=0.05) by 39% in the 7-week experi-
ment. The reduction was due to prema-
ture senescence as a result of root nec-
rosis and to destruction of feeder roots.

Fungal flora of ripening papaya fruits.
E. T. Manalastas and A. N. Pordesimo
(UPLB)

Papaya (Carica papaya L.), a very im-
portant fruit crop in the Philippines, has
been found to be infected by several
fungi in storage at ambient temperature.
According to the rate of preponderance
the following pathogenic fungi were con-
sistently found associated with the ripen-
ing papaya fruits: Fusarium solani, Colle-
totrichum gloeosporioides, Botryodiplo-
dia theobromae, Rhizopus nigricans,
Corynespora cassiicola, Penicilium sp.,
and Phytophthora parasitica. Several
species of saprophytic fungi have also
been found and these were Mucor, Peni-
cillium, Rhizopus nigricans and several
species of Aspergillus A. flavus, A.
niger, A. tamarii. The most severe
disease-causing fungus was F. solani,
capable of infecting harvested papaya
fruits in any stage of fruit development


viz., green mature, rare-ripe, and fully-
ripe. It was found to cause surface fruit
rotting and stem-end rotting. On rare-
ripe to fully-ripe papaya fruits the follow-
ing were observed: typical anthracnose
lesions caused by C. gloeosporioides, sur-
face fruit rot and stem end rot caused
by B. theobromae and C. cassiicola.
R nigricans was found to cause severe
hydrotic fruit rotting. This fungus and
Penicillum sp. commonly acted as sap-
robes on lesions incited primarily by pa-
thogenic fungi. Penicillum sp. produced
velvety or powdery lesions on fruit, and
P. parasitica caused a water-soaked lesion
on the fruit surface. The saprophytic
fungi were isolated from surface washings
of fruits or were found growing on late
ooze from wounds and hydrotic tissues.
The perceptible synergistic effect of pa-
thogenic fungi with others is predispo-
sition of the infected papaya fruits. They
hastened disease development which des-
troyed the epidermal and sub-epidermal
tissues and gave the fruits an unsightly
appearance consequently impairing the
quality and marketability.

Laboratory screening of different fun-
gicides for the control of Colletotrichum
lindemuthianum causing anthracnose of
stylo (Stylosanthes guyanensis). C. K.
Alagad, Jr. and B. P. Bambilla (CLSU)

The effectivity of the fungicides at
three concentration levels (500, 1000,
1500 ppm) to inhibit the growth of
Colletotrichum lindemuthianum was de-
termined using two techniques; first
by paper disc technique which measured
the diameter of the zone of inhibition
after 48 hr of incubation and by slide
germination technique which counted the
spores that germinated after 24 hr of in-
cubation. The following fungicides, in
descending order of effectivity: Maneb
Dithane M-45, Captan, Benlate


Vol 18









Abstracts of Papers


Delsone MX, Daconil, Vitigran blue,
and Cosan were found to inhibit germi-
nation of C. lindumuthianum. They
were most active in their concentrated
form. All fungicides except Cosan exhi-
bited inhibition zone using paper disc
technique at all concentrations. It is re-
commended to test first the three most
effective fungicides under field condi-
tion to fully evaluate their efficacy
against C. lindumuthianum,


Survey of cyst nematodes on seed
potato growing areas in Benguet. E. A.
Verzola and T. A. Khayad (BPI)

The cyst nematode (Globodera ros-
tochiensis Woll.) is one of the limiting
Factors in the selection of suitable sites
for potato seed production. The tolerance
limit allowed for cyst nematodes in the
Philippines Seed Certification scheme is
zero, hence the importance of this survey.
Sixteen (16) different locations in 232
farms in the potato producing areas in
Benguet with elevation ranging from
1600 to 2330 m above sea level were
positively infested with the cyst nema-
tode, G. rostochiensis Woll. The popula-
tion density (cyst/100 cc soil) ranged
from one (1) to 61 full cysts (a minimum
of 500 eggs/cyst) which is considered low
to severe infestation. All the infested
farms surveyed, except one, had been
in potato production for many years.

Diseases of mungbean as affected by
different levels of nitrogen and
population density. T. C. Bayacag and I.
C. Tandigan (USM)

A study on the effect of nitrogen and
population density on the incidence of
mungbean diseases was conducted at the
experimental field of Southern Mindanao
Agricultural Research Center (SMARC),
University of Southern Mindanao,
Kabacan, North Cotabato from March


1981 to June 1981. The application of
nitrogen fertilizer (21-0-0) at different
levels did not significantly affect the oc-
currence of Cercospora leaf spot, anth-
racnose, Fusarium leaf blight, pod rot,
damping-off and mungbean yellow
mosaic. However, the occurrence of Scle-
rotium wilt was significantly was affected
by the levels of nitrogen. A level of 40 kg/
ha gave the highest mean percentage in-
fection of 31.58. Population density, on
the other hand, significantly affected the
occurrence of damping-off (at seedling
stage), Sclerotium wilt (at vegetative stage
and flowering stage) and rust (at maturity
stage). Percentage infection of these
diseases increased as the population
density of mungbean increased.
Mungbean yield was significantly affected
by the different population densities but
not by the levels of nitrogen. The highest
yield of 153.88 kg/ha was obtained from
the population of 200,000 plants/ha,
followed by subsequent decrease in yield
beyond 200,000.

Grassy stunt and ragged stunt trans-
mission by a planthopper reared on
Leersia hexandra. V. M. Aguiero, R. D.
Daquioag and K. C. Ling (IRRI)

Transmission experiments were under-
taken to determine the ability of the
brown planthopper (BPH) reared on
Leersia hexandra to transmit rice grassy
stunt virus (RGSV) and rice ragged stunt
virus (RRSV). Insects at nymphal stage
were confined on Taichung Native 1
(TN1) diseased plants for 2-day acquisi-
tion feeding and 1 to 4 days on L.
hexandra for virus incubation. Daily
serial transmission tests until the insect's
death were done in test tubes using TN1
seedlings as indicator. Results showed
that 25 percent of the insects tested in 5
trials were vectors of RGSV. The number
of infected seedlings per infective insect
ranges from 1 to 5 with an average of 2
seedlings. On the other hand, 13 per-


Jan. & June 1982









Philippine Phytopathology


cent of the insects tested in 4 trials were
capable of transmitting RRSV. Seedling
infection varies from 1 to 18 with an
average of 12 seedlings per inefctive
insect. The average longevity of virulife-
rous insect tested for RGSV and RRSV
were 4.3 and 4.9 days, respectively.
Specimen of this BPH colony had been
sent to the Entomology Department,
IRRI for identification.

Assessment of yield loss due to downy
mildew of sugarcane caused by Peronos-
clerospora philippinensis (Weston) C. G.
Shaw. F. R. Husmillo (PHILSUCOM)


The effect of downy mildew on the
yield of the sugarcane variety Phil 6723
was studied. The disease significantly re-
duced the yield of Phil 6723 at varying
levels of disease infection. Reductions in
ton cane per hectare were 8.86, 11.41,
18.22 and 36.45% at 25.37, 30.51,45.14
and 85.35% infection, respectively. High-
ly significant reduction in picul sugar per
ton cane was obtained at 85.35%
infection with corresponding loss of
35.42%. No significant reduction was ob-
tained at 25.37, 30.51 and 45.14% in-
fection. Losses in picul sugar per hectare
were 10.12, 14.92, 24.46 and 58.13%
at 25.37, 30.51, 45.41 and 85.35%
infection, respectively.

Seedling root dipping in systemic
fungicide suspension for leaf blast con-
trol. J. M. Bandong and C. Q. Torres
(IRRI)

Suspensions of 1, 2, 5, 6-tetrahydro-
4H-pyrrolo(3, 2, 1-1J) quinoline4-one
(CGA49104), 50% WP and 4, 5-dihydro-
4-methyltetrazolo (1,5-a) quinazolin-5-
one (PP389JF5816), 50% WP, were eva-
luated as seedling root dips for leaf blast
control. Each compound was tested at 3
concentrations and at various dipping


duration. Blast-susceptible IR442-2-58
10-day old dapog-raised seedlings were
used in this study. Seedlings of the same
variety which served as controls were left
untreated. Immediately after the dipping
treatments, the seedlings were transplant-
ed into plastic trays containing soil and
continuously exposed to blast inoculum in
the blast nursery until the test was ter-
minated at 8 weeks after seeding. Thus
far, CGA49104, at concentrations of 1.0,
2.0 and 4.0 g formulated product/liter of
water at all treatment durations of 1, 3,
6, 12 and 24 h, exhibited very effective
leaf blast control. The efficacy of the
compound increased with concentration
and treatment duration. PP389JF5816,
although apparently less effective than
CGA49104 at the same concentrations
and treatment durations, also showed
effective leaf blast control particularly at
the 12-and 24-h dipping treatments.
The efficacy of this fungicide similarly
increased with concentration and treat-
ment duration.

Effects of fertilizer amelioration and
chemical treatment of soil with history
of severe wilt infestation on disease re-
action and yield of tobacco. A. C.
Necesito and M. C. Rana (UPLB)

Ten cultivars belonging to Virginia and
Turkish types of tobacco were screened
for disease reaction and yield under natu-
ral epiphytotics. The effects of organic
and inorganic fertilization, chemical treat-
ments of soil and the interaction of ferti-
lizer and chemical treatments of soil on
disease and yield were also investigated.
Tobacco wilt due to a bacterial pathogen
was the predominant disease in the field,
though variable incidences of mosaic,
root knot, root rot, and black shank were
noted. Two cultivars, Giant Coker and
Vista, were rated resistant to wilt under
ipil-ipil (50 tons/ha) amendment, but
were either susceptible, moderately sus-
ceptible or moderately resistant under
carabao manure (50 and 100 tons/ha) and


Vol. 18









Abstracts of Papers


6-9-15 (40 kg NPK/ha) amendments. No
cultivar was rated resistant in carabao
manure and 6-9-15 ameliorations.
Generally, wilt severity was higher in
plots with carabao manure than with ipil-
ipil and 6-9-15 ameliorants. Formaldehyde
(20v/v) in combination with either cara-
bao manure, ipil-ipil or 6-9-15 was more
effective than methyl bromide (2 lbs/108
m2) in reducing wilt incidence among
tobacco cultivars. Maximum plant height
and leaf yield were obtained from plots
receiving ipil-ipil and formaldehyde. Yield
loss was positively correlated with rate of
infection in a multiple-point model.

Wilt disease of coconut in Soccoro,
Oriental Mindoro: 1977-1981 Survey. E.
C. Concibido, R. G. Abad and J. G.
Nuevas, Jr. (PCA)

A fatal wilt disease of coconut in the
Philippines occurs in Socorro, Oriental
Mindoro. Accordingly, it was first
observed in the early 60's and has killed
an unestimated number of palms in the
area. From surveys of 1977 to 1981, the
disease was present in 6 barangays of
Socorro. For the same period nearly
7,000 palms (mostly 25 years old and
below) were reckoned to have succumbed
to the disease. The disease still continues
to occur despite the 'cut and burn' ope-
rations conducted in 1977, 1978 and
1980. The disease spreads in a 'leap frog'
pattern suggesting infectious nature of
the malady, probably disseminated by air-
borne vector(s). The 4 surveys conducted
within 5 years also showed a yearly
average disease incidence of 1.4, 1.03,
4.06 and 0.85%. The high figure for the
third survey is attributed to the com-
bined incidence rate of 2 years (1979-80).
There are unconfirmed reports that the
disease is present in other municipalities
of the province. It can be concluded that
the disease is an alarming one hence re-
search on etiology and especially control
measures are of paramount importance.


Influence of vector age on rice ragged
stunt virus (RRSV) transmission. R. D.
Daquioag, V. M. Aguiero and K. C. Ling
(IRRI)

When Nilaparvata lugens at ages of 1,
5, 10, 15, and 20 days after hatching
were tested by daily serial transmission
after an acquisition feeding on diseased
plants for 4 or 8 days, the 5-day-old
brown planthoppers gave the highest
percentage of infective insects, although,
it did not differ markedly from that of 1-
and 10-day-old BPH. The percentage of
infective insects and the number of seed-
lings infected per infective insect tend i to
decrease as the vector becomes older.

Comparative effects of two emulsifiers
in Sigatoka spray mixtures. M. O. San
Juan (TRRC)

Spray mixtures of fungicide-oil-triton-
water to control sigatoka and black leaf
streak diseases have been in use after the
discovery of spray oils to be fungistatic.
Since then the use of an emulsifier increas-
ingly became important. Majority of the
emulsifiers are nonionic. Its role is to
effect a good oil-water emulsion in the
spray mixture. Among several emulsifiers
tested, Luthensol A8 and Triton X-45
are commercially used in most banana
plantations. Addition of the emulsifier
is usually at a concentration of 1 to 1.5%
of the spray oil being used in the mixture.
Luthensol A8 was found to be statistical-
ly significant in its emulsifying activity
over the Triton X-45 as shown by the
delayed infection and incubation period
of the disease. Price differences of the
two emulsifiers, however, favor the use of
Triton X-45 by most cost-conscious
banana growers.


Jan. & June 1982









Philippine Phytopathology


Genetic analysis of bacterial blight re-
sistance in rice I. Inheritance of resistance
of CAS 209. A. Yoshimura, T. W. Mew
and G. S. Khush (IRRI)

The mode of inheritance for resistance
to Pxo 86 which is a representative isolate
of pathotype II of bacterial blight of rice
bacterium, Xanthomonas campestris pv.
oryzae in a rice cultivar 'Cas209' and the
linkage relationships of the gene with
known genes, Xa-4 and Xa-5 were
studied. The study of F1, F and the
backcross populations from tie crosses
with susceptible cultivars revealed that
the resistance of Cas209 was controlled
by a single dominant gene. The tests
for linkage relationship indicated that
the dominant gene newly identified was
linked to Xa-4 with a recombination
value of 28.3% and the gene was in-
dependent of Xa-5. The dominant gene
of Cas209 was suggested to be a new
gene for resistance to bacterial blight.

Diplodia boll rot of cotton: Pathogeni-
city and histopathology. E. B. Gergon
(CRDI-MMSU)

Diplodia boll rot of cotton in the
Philippines is caused by Diplodia gossy-
pina Cke. Early symptoms of the disease
appeared as circular, dark brown, water-
soaked and somewhat sunken spots which
soon enlarged and involved the whole
bolls. In advanced stage, the boll turned
black with pycnidia and pycnidiospores.
The fungus infected injured and unin-
jured bolls at all stages of development,
being most destructive on ages seven days
or below or 40 days or older. Penetration
of the fungus through uninjured bolls
directly through the epidermis of 10-day
old bolls and through the stomata or
epidermis of bolls 20-days old or older.
The hyphae invaded the epidermal cells
and the parenchyma of the mesocarp
inter- and intra-cellularly.


Effects of five nematicides on the
control of nematodes and yield of
tomato. R. G. Davide and R. A. Zorilla
(UPLB)

Nemacur 10G, Temik 15G, Furadan
3G, Mocap 5G and Vydate 10G greatly
reduced root-knot nematode (M.
incognita) infection in tomato. Popula-
tion densities of other plant parasitic
nematodes were also affected by the
nematicide treatment. As a result of the
nematode control, a highly significant
yield increase was obtained ranging from
6 to 122%, 40 to 96% and 28 to 109% in
the 1979, 1980 and 1981 trials,
respectively, using var. VC 11-1. The high-
est yield increase of 122% resulted from
Nemacur 10G treatment, followed by
Temik 15G, Furadan 3G, Vydate 10G
and Mocap 5G treatments.

Banana spray oils for the control of
Sigatoka and black leaf streak diseases.
M. O. San Juan (TRRC)


Sigatoka, also known as yellow siga-
toka, caused by Cercospora musae and
black leaf streak caused by Mycosphae-
rella fijiensis, are the two most common
foliage diseases of bananas. They are
serious in most plantations during the
rainy months. In Davao Province, the
heaviest rains in June and December pre-
ceed disease flare-ups 4 to 6 weeks later.
Chemical control of these diseases is
usually a combination of fungicide, oil,
triton and water. Experimental results
show that spray oils inhibit the growth of
the fungus. It provides an additive effect
to the spray mixture. The spray oils that
have been tested so far are Orchex,
Australian Neutral Fruit Spray Oil, Caltex
Fruit Spray Oil CT, Shell Banana Spray
Oil, Shell Banana Liquid Fungicide (BLF
84) Filoil Banana Spray Oil 70 and Gulf
Orchard Spray Oil 70. All these oils have
their respective specifications as to vis-
cosity, specific gravity, unsulforated


Vol. 18









Abstracts of Papers


residence etc. The Shell Banana Spray Oil
with unsulfonated residue of 93.8% and
Caltex Fruit Spray Oil CT with 94.6% are
the ones used in most banana plantations
in Mindanao.

Survey and identification of diseases
attacking ornamental plants N. C. Bani-
qued (BPI)

Survey conducted in the different
nurseries and experiment stations on
germplasm collection of ornamental
plants resulted in the identification of
leaf spot, anthracnose, ring spot, mosaic,
rust, stem rot, and powdery mildew
diseases. The different pathogens found
in association with these various diseased
plants were species of Cercospora, Col-
letotrichum, Rhizoctonia, Sclerotium,
Oidium, Uromyces, Helminthosporium,
Aliernaria, Fusarium Chetothyrium and
virus. The leaf spot and stem rot diseases
were commonly noted during the rainy
season while ring spot mosaic and rust
diseases were observed during the summer
months. Powdery mildew was very
serious from November to March. This
was probably brought about by cool
nights and excessive soil moisture. The
diseases identified caused 10-30 per-
cent damage to the plants.

Damping-off disease of tobacco: Oc-
currence, distribution, and screening for
resistance. P. N. Dipon and R. G. Davide
(PTRTC-UPLB)

Four of the five pathogens reportedly
causing damping-off of tobacco were iso-
lated by the baiting technique and
through the use of selective media from
135 samples collected from seven
tobacco-growing provinces in Northern
Luzon, namely: Ilocos Norte, Ilocos Sur,
La Union, Pangasinan, Cagayan, and
Isabela.
The pathogens isolated were Pythium
sp., Fusarium oxysporum f. nicotianae,
Rhizoctonia solani and Sclerotium rolfsii.


Phytophthora parasitica var. nicotianae
was not detected. Pythium sp. and F.
oxysporum f. nicotianae were the most
common and present in all samples. R.
solani and S. rolfsii occurred very rarely
and were not present in the samples col-
lected from the provinces of Cagayan and
Abra, respectively. Pathogenicity of the
four pathogens were tested on tobacco
var. Golden Harvest. Pythium sp. was the
most virulent followed by F. oxysporum
f. nicotianae, R. solani and S. rolfsii.
Resistance of tobacco to these four
pathogens was observed mainly in the
Virginia types. All of the filler and wrap-
per types were highly susceptible. Coker
139 and Dixie Bright 102 were resistant
to S. rolfsii, while Buyers Choice, Coker
411, Coker 136, Oxford 26, Yarda, and
100 leaves were moderately resistant.
Coker 411, Coker 139, and Dixie Bright
102 were resistant to F. oxysporum F.
nicotianae, while Coker 136 and Reams
66 were moderately resistant. Virginia
21 was resistant to R. solani, whereas
Coker 411, NCBY, and Harrison Special
were moderately resistant. However,
NCBY, Coker 139, and Dixie Bright
102 were only moderately resistant to
Pythium spp.


The effective concentrations of carbon
dioxide, streptomycin, potassium per-
manganate, and copper sulfate against
Erwinia carotovora on cabbage. P. M.
Halos and F. T. Faner (UPLB)

The effective concentrations that
could retard symptom appearance of Er-
winia soft rot on cabbage at 15C incuba-
tion were 10% for CO2 and 100 ppm for
streptomycin, potassium permanganate
and copper sulfate. At these concentra-
tions, the storage life of cabbage could
be prolonged by approximately 1 week
even with the inoculation of Erwinia
carotovora.


Jan. & June 1982









Philippine Phytopathology


Economic hosts of Pseudomonas sola-
nacearum isolates from abaca. A. Rillo
(PCA)

Eleven economic plants belonging to 5
families were artificially and naturally
inoculated with P. solanacearum isolates
from abaca. Results showed that potato,
castor bean, eggplant, tobacco, tomato,
diploid banana, abaca, and heliconia
were infected upon artificial inoculation
with the organism. Under natural condi-
tions, however, only castor bean, tomato,
and eggplant were infected. The isolates
failed to infect abaca under natural
conditions suggesting the possible role of
biotic or abiotic agents in disease occur-
rence. The results of the study showed
that the organism exists as a variable
species with various pathogenic po-
tential in plants.

Simultaneous and sequential transmis-
sion of abaca-mosaic and banana-mosaic
viruses to abaca (Musa textilis Nee) by
Aphis gossypii Glover. M. L. Retuerma
(BPI)

Abaca-mosaic and banana-mosaic
viruses were simultaneously or sequential-
ly transmitted to abaca (Musa textilis
Nee) by a common vector, Aphis gossypii
Glover. Both viruses transmitted to abaca
have no interference or antagonistic
effect to each other but produced more
severe symptoms and stunted growth
than single infection of either viruses.
Each virus acts independently by pro-
ducing its own typical symptoms in the
same host. Flexuous rod-like, isometric
virus particles measuring 650-750 nm in
length and 28-30 nm in diameter, respec-
tively, were both observed under the elec-
tron microscope in crude sap extracted
from abaca used in simultaneous and
sequential transmission tests. Positive
serological reaction was observed only
against cucumber mosaic virus Y(CMV-Y)
antiserum.


Biochemical mechanisms of mimosine
toxicity in Sclerotium rolfsii. E. P.
Serrano, L. L. Ilag and E. T. Mendoza
(IPB)

Studies were conducted to explain the
biocidal activity of mimosine against Scle-
rotium rolfsii, a pathogen of mungbean.
The mycelial growth of Sclerotium
rolfsii in the presence of 2.5 mM
mimosine was reduced to 40-60%,
and was generally thinner, brownish and
not cotton-like in appearance. Mimosine
also prevented the further formation of
sclerotial bodies. This inhibitory action of
mimosine was best reversed by pyridoxal-
5-phosphate (78%) followed by amino
acid analogs tyrosine and tryptophan
(50%). Phenylalanine has little effect.
Among the metal ions Fe ) most effect-
ively decreased mimosine's inhibitory
eff ct (92% at 10 mM Fe3+) followed by
Al (80% at mM Al ) while Fe+ and
Cu2+ exhibited the least counter-effect
(about 25% and 35%, respectively at 5
mM Fe + or Cu2+). Mimosine decreased
the specific activities of aspartate transa-
minase and tyrosinase by as much as 37
and 74%, respectively while reducing that
of amylase by only 25%. Mimosine inhi-
bited aspartate transaminase activity non-
competitively with a K1 of 0.056 mM.
Tyrosinase activity was inhibited by
mimosine competitively with a K1 of
0.089 mM. ATP production in minosine-
grown cells was reduced by 70%.
Decreased DNA and protein synthesis
shown by lower incorporation
3H-tyhymidine and 4C-phenylalanine
were observed. Little or no effect on
RNA synthesis was evident. Cell-free
extracts of S. rolfsii degraded mimosine
slightly into 3-hydroxy-4(1H)-pyridone
(DHP), mimosinic acid and an uniden-
tified compound. A large amount of
undergraded mimosine remained. No
further metabolism of DHP was observed.


Vol. 18









Abstracts of Papers


Sweet potato sucrose agar: An
inexpensive culture medium for fungal
growth. L. L. Ilag and A. R. Pua (IBP)

Sweet potato sucrose sugar or SPSA
(composed of sweet potato, 200 g; suc-
rose from brown sugar, 17 g; agar bar or
"gulaman," 15 g; tap water allowed to
stand for 24 hours, to make one liter)
was found to be an excellent substitute
for potato dextrose agar (PDA). Seven
test fungi exhibited better mycelial
growth and higher sporulation in SPSA
than in PDA. The fungi tested were
Stemphylium lycopersici (Enjoji) Yam,
Colletotrichum gloeosporioides Penz.,
Pythium debaryanum Hesse, Rhizopus
nigricans Ehr., Aspergillus flavus Lk. ex
Fries, Volvariella volvacea (Bill. ex Fr.)
Sing. and Fusarium moniliforme Sheldon.
SPSA not only supported good fungal
growth, its ingredients are inexpensive
and are readily available locally.

Synergism between endomycorrhizas,
Rhizobium japonicum CB 1809 and soy-
bean (Glycine max). P. M. Halos, E. M.
Luis and M. S. Borja (UPLB)

Soybean plants responded differently
to the 8 exotic and indigenous endomyc-
rhizal isolates both in field and pot
experiments. Differences in mean height
between treatments were significant. Ino-
culated plants were noticeably larger,
taller, greener, healthier, and more vigo-
rous than the control plants. In the field
experiment, the number of pods, yield,
dry weight and height of soybeans ino-
culated with endomycorrhizas and R.
japonicum were significantly higher than
those of plants inoculated with either
endomycorrhizas or R. japonicum alone.
Not all plants inoculated with the
endomycorrhiza isolates alone exhibited
significant nodule formation. However,
when such isolates were combined with
R. japonicum, the plants showed striking-
ly increased nodule formation compared
with plants inoculated with R. japonicum


alone.

Computer simulation of corn leaf
blight. A. D. Raymundo (IPB)

A simple model of leaf blight of corn
caused by Helminthosporium turcicum
Pass. was developed using the state-
variable approach. Modeling involved
partitioning the monocycle component of
the polycycle into five components:
lesion number, lesion growth, sporulation,
dispersal, and deposition. Each of the
components was considered a sub-model.
Computer simulation was done by
integrating the sub-models using the
Continuous Systems Modeling Program
(CSMP) III computer language on IBM
370/25. The general model has been used
to generate theoretical resistance media-
ted disease progress curves.

Inheritance of resistance to leaf scald.
F. L. Nuque, C. Q. Torres, A. Obusan
J. P. Crill (IRRI)

A study was conducted to determine
the inheritance of resistance to an isolate
of Rhynchosporium oryzae in 7 cross
combinations of rice varieties. Plant were
inoculated 45 days after seeding in the
greenhouse following the clipping
method. The Fl's of the cross between
resistant and susceptible IR36 showed
resistant reactions indicating that
resistance is dominant. The progenies of
the different cross combinations between
resistant varieties Suntang Biringin,
Melot, Tjele, Montje Wowo and susceptible
variety IR36 segregated into 3:1 ratio of
resistant to susceptible plants suggesting
the presence of a single dominant gene
for resistance. All plants in the F2's of
crosses among susceptible parents IR36,
Kolai and Rama were susceptible.

Some studies on bacterial stripe of
rice. M. R. Baraoidan, T. W. Mew and T.
Aballa (IRRI)


Jan. & June 1982









Philippine Phytopathology


A disease exhibiting the symptoms of
bacterial stripe was observed on rice seed-
lings at IRRI farm. Lesions appeared as
water-soaked to brown longitudinal
stripes on leaf sheaths and leaves. In
severe cases of infection, the disease may
cause seedling stunting, rotting of the
shoots and the subsequent death of the
plant. Survey of 11 seedbeds at IRRI
showed disease incidence ranging from
0.5 to 7.5% on 14 rice varieties and lines.
The lowest and highest infections were
observed on IR42 and IR50, respectively.
The organism isolated from naturally in-
fected seedlings was pathogenic to rice
seedlings. Based on symptomatology,
morphological, cultural and physiological
characteristics, the causal organism was
found very closely related to Pseudomo-
nas setariae, the causal organism of bacte-
rial stripe of rice in Japan and of Italian
millet.
Bacterial stripe occurred on seedlings
of six rice varieties grown from seeds ob-
tained from different sources. The
development of the disease on seedlings
from seeds grown in sterile soil indicated
that the baterium did not come from the
soil. Furthermore, infection on seedlings
from disinfected seeds sown in sterile
soil indicated that the bacterium was not
on the outside of the seedcoat but most
likely inside the seeds. Bacterial stripe
developed at 2-leaf stage of rice seedlings
of IR40 and IR52 varieties from seeds
that were dipped instantly for 5 seconds
or soaked for 24, and 48 hr in bacterial
suspension. Water-soaked lesions
appeared on the coleoptile and progressed
either to the leaf sheath, primary or to
the secondary leaf. The results showed
that the incidence of the disease increased
from instant dipping to 24 hr soaking.
However, at 48 hr soaking the incidence
of the disease decreased. Severely infect-
ed seedlings eventually died. Seeds col-
lected from plants inoculated at booting
and at flowering stages produced infected
seedlings indicating that the bacteria re-


mained viable in the seed and cause
infection on the seedlings.

The isolation, pathogenicity and
identification of a fungal parasite of Pe-
naeus monodon Fabicius. Q. M. Bautista,
Jr. and L. L. Ilag (MSU-UPLB)

A fungus was isolated from an infected
population of Penaeus monodon Fabri-
cius zoea in the hatchery tanks of the
Technology Resource Center of the Min-
danao State University-Institute of
Fisheries Research and Development,
Naawan, Misamis Oriental on February
12, 1981. The fungus had non-septated,
branched hyphae when young, and
sparingly septated, branched with stout
or stubby portions at maturity. During
vesicle formation a slender hyaline cres-
cent was formed at the apex. The fungus
was holocarpic and formed vesicles
wherein zoospores differentiated. The
vesicle may be persistent or non-persist-
ent. The isolate is believed to be an un-
reported species of Lagenidium. Different
stages of P. monodon reacted differently
to zoosporic attack. The zoea and mysis
were the most susceptible stages. The egg,
nauplius, and post-larvae showed a de-
creasing susceptibility, in that order.

The interrelationships of Radopholus
similis and Meloidogyne incognita on
banana. W. Santor and R. G. Davide
(UPLB)
The interrelationships ofR. similis and
M. incognita in three varieties of banana
(Saba, Bungulan, and Giant Cavendish)
were studied in two sets of experiments
using inoculum levels of 1,000; 5,000 and
10,000. All three varieties of banana
showed equal susceptibility to infections
by both species of nematodes. The num-
ber of lesions and galls were more in
plants inoculated singly with R. similis
and M. incognita than in those
inoculated by both species. Higher popu-
lation counts of R. similis and M. incog-


Vol. 18









Abstracts of Papers


nita were, likewise obtained from plants
inoculated with either species alone than
those of the combinations. The popula-
tion of M. incognita was reduced when
R. similis was inoculated ahead of M. in-
cognita. M. incognita in different stages of
development were greatly reduced when
combined with R. similis or when R.
similis was inoculated first. Cellular ob-
servations of galled roots with Radopho-
lus lesions showed the deleterious effects
of R. similis on the giant cells of M.
incognita and undoubtedly would
become a dominant species and cause
more damage to banana plant.

Toxigenicity of Xanthomonas cam-
pestris pv. oryzae. G. P. Singh and T. W.
Mew (IRRI)

Culture filtrates of Xanthomonas cam-
pestris pv. oryzae from Wakimoto's and
Dye's modified media caused wilting and
leaf yellowing in rice seedlings with
partially excised roots within 36 hours,
indicating the toxin production by the
pathogen in culture. However, aeration
and age of the culture were found to
show marked effect on the phytotoxicity
of the filtrates. The culture filtrates also
delayed the seed germination and caused
partial root browning and growth reduct-
ion in rice seedlings. Attempts to cha-
racterize the toxic components indicated
the presence of different toxins in the
culture filtrate which vary in their heat
stability and dialysability. The major
component responsible for wilting
appeared to be heat stable. One of the
main component possibly responsible for
wilting and yellowing was found to be
dialysable while the other non-dialysable.

Determination of the probable causes
of deterioration of pilinut seeds in
storage. M. L. M. Oropesa and A. N. Por-
desimo (UPLB)

Random samples of 100 pilinut fruits
(Canarium ovatum Engler) taken monthly


from three separate batches of stored nuts
depulped by three customary processes,
viz., pounding, cold-water, and hot-water
treatments,were cracked and observed
for the degree of deterioration in storage
at ambient temperature. Microflora as-
sociated with the rotting kernels were
characterized and identified as Aspergillus
glaucus (Thom and Raper), A. flavus
(Link), A. terreus (Thom), A. ochraceus
(Wilhelm), A. fumigatus (Fresenius), A.
nidulans (Eidam), A. restricts (Smith),
Penicillium sp., and Rhizopus sp.
The ten months of observation
representing 10 sampling periods revealed
that 25% deteriorated kernels for the
hot-water, pounding, and cold-water
treatments occurred on the 5th, 6th, and
8th sampling periods, respectively. The
highest kernel deterioration of 70% was
observed to occur only under the hot-
water treatment on the 10th sampling
period. The rate of deterioration was
directly related to duration of storage.
The depulping process of hot-water treat-
ment appeared to predispose kernels to
deterioration.

Effect of age of rice ragged stunt virus
(RRSV) source on transmission. V. M.
Aguiero, R. D. Daquioag and K. C.
Ling (IRRI)

Potted TNI seedlings were inoculated
by viruliferous insects for one day. Only
those plants which showed typical symp-
toms of ragged stunt disease were used
in this experiment. Brown planthoppers
were allowed to feed on the diseased
plants from 20 to 135 days after inocula-
tion for 8 to 14 days. The percentage of
infective insects varied not only among
acquisition access times but also among
ages of RRSV sources. As the acquisition
access time lengthened, the percentage of
infective insects increased. Younger
diseased plants seemed better RRSV
sources older diseased plants.


Jan. & June 1982









Philippine Phytopathology


Vein necrosis threatens rambutan pro-
duction. A. N. Pordesimo (UPLB)

First reported to occur in Victoria,
Oriental Mindoro in 1967, vein necrosis
of Rambutan (Nephelium lappaceaum L.)
has become a serious threat to this fruit
crop in Laguna. The disease has already
defoliated quite a number of trees that
have been rendered unproductive during
the past two fruiting seasons. Its primary
cause has earlier been reported to be a
bacterium with the proposed name Xan-
thomonas nepheliae sp. n. At a distance,
affected trees are either leafless or have
dried leaves and limbs dangling from
branches. Infected leaves are easily recog-
nized by the presence of dark necrotic
areas along the veins and angular spots on
leaf blades. The disease also affects seed-
lings. It is especially destructive to succu-
lent tissues such as leaf buds and young
leaves. During dry periods, resinous gra-
nules are detectable along the infected
tissues particularly the midveins.
Epiphytotic outbreaks have been
observed to coincide with the rainy pe-
riods and stormy weather. Due to its
apparent destructiveness, it deserves
urgent attention to suppress its further
spread. Recognition of its diagnostic
symptoms will enable backyard and
orchard growers to remove and destroy
infected plant parts and practice strict
sanitation within orchards.

Fungicide foliar sprays for sheath blight
control on rice. J. M. Bandong and A.
Obusan (IRRI)

Fungicide samples were evaluated as
sprays, in separate screenhouse tests, for
sheath blight control on IR50 and
IR1317 seedlings grown in rows of 5 per
plastic tray containing soil. The first
spray was applied on seedlings at about
3 to 5 weeks after seeding. Two sub-
sequent spray applications were made at
weekly intervals. Rice grain-hull sheath
blight fungus culture was used to ino-


culate the test plants a day after the first
spray was applied. Four disease readings,
based on % infection of leafsheaths and
leafblades, were made on the seedlings;
the first one, a week after the first spray
application and the rest, weekly there-
after. Two compounds, 1-(p-chlorophe-
nyl)- -cyclopentyl-3-phenylurea (NTN
19701), 25%WP, applied at the rate of
1.0 kg formulation/2,000 1 suspension
and triphenyltin acetate, 60%WP at 0.5,
0.75 and 1.0 kg rates, very effectively
reduced sheath blight disease severity on
the test plants until the tests were termi-
nated 4 weeks after the first sprays were
applied. Other compounds such as N-
(3,5-dichlorophenyl)-5-methyl-5-carbe-
toxy-1, 3-oxazolydin-2,4-dione (Serinal)
50%WP; thiophanate methyl (Fungitox),
70%WP; each applied at the rate of 1.0
kg formulation, and 1-(2,4-dichlorophe-
nyl)-4.4-dimethyl-2-(1,2,4-triazol-l-yl)-
pentan-3-ol (PP296), 12.5%w/v, at 1.0
liter, effectively reduced disease seve-
rity on seedlings. However, PP296,
although effective for sheath blight con-
trol suppressed plant height.
Isolation, characterization and identifi-
cation of the organsim causing leaf spot
of stylo (Stylosanthes guyanensis var.
Schefield). C. K. Alagad Jr. and C. G.
Mallari (CLSU)

The leaf spot of stylo is caused by
Colletotrichum lindemuthianum Sach and
Magnus. Symptoms appeared as dark
brown, elongate more or less angular leaf
spots which appeared on the veins of the
lower side of the leaf. Petioles and stems
also bore lesions. In host tissues, acervuli
were fully developed and rose on the
epidermal tissues. Scattered throughout
the acervulus were thick walled, dark
brown setae measuring 26 to 83 u. longer
than the conidial mass. Hyphae were
branched, septate, hyaline at first
becoming dark color with age. Conidia
were continuous, hyaline, granulose, 1-2
guttulate, oblong, cylindrical with ends


Vol. 18









Abstracts of Papers


rounded and with an average measure-
ment of 5.2 x 12.4 u. One to four germ
tubes grew from a conidium. On potato
dextrose agar, the fungus produced very
little aerial white mycelia, and well or-
ganized acervuli scattered over the surface
of the colony. Conidia were produced in
profusion in the acervuli, being visibly
pink to orange-colored masses. On
maturity, the mycelia turned blackish
with numerous black sclerotial-like bodies
at the surface of the agar. The growth of
the organism was favored at a tempera-
ture of 20 to 30 C, pH range of 5 and 6,
aerial mycelial growth increased with de-
creased light duration.

An unknown disease of rice transmit-
ted by the brown planthopper Nilapar-
vata lugens in the Philippines. P. Q. Ca-
bauatan (IRRI)

An unknown disease of the rice plant
was observed at the International Rice
Research Institute (IRRI), Laguna, Philip-
pines. The disease was prevalent in fields
where the brown planthopper (bph) in-
cidence was high. At a distance, the in-
fected plants look like the rice tungro
disease. The symptoms of the disease are
stunting, mottling (mosaic), narrowing and
yellowing of the leaves, erect growth
habit, and premature death of infected
plants. When five-day old brown plant-
hopper nymphs were given access to the
diseased plant for 4 days and transferred
serially to seven-days old Thaichung
Native 1 (TN1) seedlings, positive trans-
mission of the disease was obtained.
On the other hand, negative transmis-
sion of the disease was obtained using
other insects like Nephotettix virescenes,
Recilla doraslis and Sogatella furcifera.
The symptom of the disease was ob-
served 7 to 14 days after inoculation. The
early symptoms consist of stunting,
yellowing and narrowing of the leafblade.
Irregular brownish blotches and chlorotic
streaks (mosaic) can be observed on the
discolored leaves. Preliminary results of


transmission studies showed that the
causal agent persists in the insect vector.
The infective insects continue to trans-
mit the causal agent even after molting
hence, there is no transtadial blockage.
The incubation period of the causal agent
on the insect ranges from 5 to 21 days,
mostly 6-8 days (ave. 8.4 days). Five to
30% of the insects used in separate tests
were active transmitters. So far, the
longest retention obtained was 33 days.
The other diseases transmitted by the
brown planthopper are grassy stunt,
ragged stunt and wilted stunt (reported
in Taiwan). The unknown disease is quite
similar to rice wilted stunt based on
symptomatology and virus-vector,
relationship. However, the causal or-
ganism of the rice wilted stunt has not
been identified so far. Studies of the
other related factors are underway.

A preliminary survey of plant parasitic
nematodes on garlic, cassava, corn and
cotton in Ilocos and the Visayas regions.
C. A. Baniqued (BPI)

A survey of plant parasitic nematodes
attacking agricultural crops in Ilocos and
Visayas Regions showed abundance of
Rotylenchus and Pratylenchus spp. on
cotton and corn. However, garlic and
cassava did not harbor high nematode
count.

Inheritance of resistance to bakanae
disease of rice. F. L. Nuque, K. C. Chuke,
T. Vergel de Dios and J. P. Crill (IRRI)

The inheritance of resistance to three
races of Gibberella fujikuroi (Saw.) Ito
was studied. Progenies of six crosses of
IR32, IR46, IR50, IF7790-18-1-2 and
IR9703-41-3-3-1, were inoculated
separately with pathogenic races FA-1,
FH-1 and Fl-1 by soaking the seeds in
spore suspension of the fungus. The Fl's
of crosses between resistant and suscepti-
ble parents were resistant to the disease
indicating that resistance was dominant.


Jan. & June 1982









Philippine Phytopathology


The resistance in IR44/IR50, to race Fl-1,
FH-1 and FA-1 was apparently controlled
by the same duplicate genes. Resistance
in 1R44/1R7790-18-1-2 was governed by
duplicate genes to race Fl-1 and a single
dominant gene to race FH-1 and FA-1. A
single dominant gene in IR32/IR44 con-
trolled the resistance to races Fl-1, FH-1
and FA-1. The resistance in crosses
between IR46 and different susceptible
parent varied depending on races used. In
IR50/IR9703-41-3-3-1 the F2 progenies
segregated into 13:3 ratio of resistant to
susceptible plants indicating the presence
of inhibitory or suppressor genes to races
Fl-1 and FH-1. Resistance in IR 50 to
race FA-1 is controlled by a single domi-
nant gene.

Pathologic responses of banana varieties
at the UPLB genebank to Sigatoka. M.
Pantua and A. N. Pordesimo (UPOLB)

The pathologic responses to Sigatoka
of 80 varieties of existing banana plants
at the UPLB Banana Genebank were eva-
luated under conditions of natural
infection prevailing in the locality. Variety
reactions were based on percentage
yellow streak formation, degree of leaf
spotting, number of green leaves, number
of standing leaves and rate of leaf
emergence. On the basis of the observed
incidence and severity of spotting, the
varieties were rated as highly suscpetible,
susceptible, partly resistant, resistant and
highly resistant. Majority of varieties be-
longing to AA diploid and AAA triploid
groups were high susceptible. The degree
of susceptibility in the AAB group ranges
from susceptible to highly resistant, all
the ABB type clones were resistant and
the BB diploid type Clone is highly
resistant. Results of the present study
suggest that there are 2 major factors
concerned in the pathologic response of
the varieties to Sigatoka: the first is
genetic and the second is the effect of the
prevailing environmental condition in the
locality.


Inheritance of resistance to brown
spot. F. L. Nuque, B. A. Estrada, A.
Obusan and J. P. Crill (IRRI)

Studies were conducted to determine
the inheritance of resistance of nine
crosses to isolates Ho-22 (race HB-1) and
Ho-2 (GH-1) of Helminthosporium ory-
zae. Thirty-day old seedlings were inocu-
lated separately with each of the two
isolates using the injection technique.
Results showed that F1 populations of
Sekiguchi Asahi/IR36, IR36/IR14753-
120-3, IR9763-11-22-2/IR36, IR9846-
215-3/IR36, IR976445--2-/IR36,
IR9763-11-2-2-2/IRI4753-120-3, IR9764
45-2-2/IRI4753-120-3, IR9264-321-3/
Seiguchi Asahi and IR9264-321-3/
IR9846-215-3 were all resistant to isolate
Ho-22. The F2 progenies of IR9846-
215-3/IR36 and IR976445-2-2/I$36
segregated into 3:1 ratio of resistant to
susceptible plants against isolate Ho-22
(race HB-1) suggesting that resistance is
governed by a single dominant gene. The
segregation of F2 populations of S.
Asahi/IR36 and IR9264-321-3/S. Asahi
crosses gave a 9:7 ratio of resistant to sus-
ceptible plants indicating that resistance
is controlled by two pairs of complemen-
tary genes. F2 progenies of other crosses
segregated into 13:3 ratio of resistant to
susceptible plants indicating the presence
of inhibitory genes. The F2 progenies of
resistant parents IR36 and IR14753-
120-3, were all resistant. All the F1 and
F2 populations of the above crosses were
susceptible to isolate Ho-2 (race HG-1).

Effect of leaf wetness and constant
temperatures on infection by Helmin-
thosporium oryzae B de Haan. A.
Obusan, F. L. Nuque, T. Vergel Dios and
J. P. Crill (IRRI)

Different dew periods of 25 C were
used to determine the length of leaf wet-
ness that will favor the fungus to cause in-
fection on rice. No lesions were observed
on inoculated seedlings with leaf wetness


Vol 18









Jan. & June 1982


of less than 8 h. The number of brown
spot lesions on the leaf increased as the
period of leaf wetness was increased from
8 to 20 h. However, the number of le-
sions decreased as the length of leaf wet-
ness was increased to 24 h. Three constant
temperatures of 100% RH were used in
the experiment to determine the opti-
mum temperature for lesion formation.
The results showed minimum number of
lesions of 3.3 spots per plant at 15C and
highest at 25 C with 14.5 lesions per
plant. Three weeks after inoculation the
number of lesions were counted on the
leaves of the plants to ascertain whether
or not lesion number will increase. Lesion
number increased from 3.3 to 5.2 at 15 C,
3.6 to 5.3 at 20 C and 14.5 to 39.7 at
25 C. The temperature of 25 C appeared
most favorable for brown spot develop-
ment.
Greenhouse test of some fungicides for
the control of onion bulb and root rot
diseases. P. M. Halos and B. Corcolon
(UPLB)

Seed treatment with Rovral, Daconil,
Delsene MX and Difolatan were effective
against onion bulb and root rot pathogens
resulting in high percentage of seedling
emergence. Other fungicides like Benlate,
Dithane M45 and Vitigran Blue also gave
satisfactory increase in the seedling stand
compared to the control. Delsene MX,
Difolatan, Daconil, Dithane M-45, Ben-
late and Cruzate M significantly increased
the height of seedlings. Except Delsen
MX, all of the chemicals had short
residual effectiveness.

The effect of custard-apple and neem
seed oil on the survival of Nephotottix
Svierescens Distant and its transmission of
rice tungro virus. V. Mariappan, R. C.
Saxena and K. C. Ling (IRRI)

Oil extracted from seeds of custard-
apple (Annona squamosa Linn.) and
Indian neem (A. adirachta indica A. Juss)


was found to be highly effective in reduc-
ing the survival of N. virescens and its
transmission of rice tungro virus in oil-
treated TN1 seedlings. The mean percent-
age survival of and tungro transmission by
N. virescens exposed from 1 to 4 days on
plants sprayed with custard-apple and
neem oil at concentrations of 5, 10, 20,
30, and 50% were significantly different
from those exposed at the same number
of days on plants sprayed with water +
0.1% teepol (control). A significant
difference was obtained from the oil
treatment at different concentrations.
The higher 'the oil concentration, the
lower percentage of insect survival and
tungro transmission obtained in both oil
treatments. The low percentage of insect
survival and tungro transmission in oil-
treated plants was attributed to the anti-
feedant and toxic effects of custard-apple
and neem oil on N. virescens.

Genetic resistance to Philippine corn
downy mildew. M. S. Tolentino, A. D.
Raymundo, L. A. Ebron and E. A. Perez
(UPLB)

Breeding for resistance to Philippine
corn downy mildew caused by Peronos-
clerospora philippinensis Weston at the
Institute of Plant Breeding has involved
the screening of new germplasm and the
evaluation of advanced breeding materials
from populations undergoing selection
for yield. In 1981, a new dimension was
added to the program. New entries found
resistant to the disease in the screening
nursery were composite into several
populations. These populations, grouped
according to geographical source, are
undergoing further selection with
emphasis on downy mildew resistance. In-
bred lines have also been derived from
outstanding composites and have been
used in a survey of the existence of
pathogenic variants of P. philippinensis.


Abstracts of Papers









Philippine Phytopathology


Effect of artificial inoculation on seed
infestation and seedling infection by
Fusarium moniliforme. J. M. Bandong
and T. Vergel de Dios (IRRI).

The availability of highly infested
seeds with the bakanae fungus is very
necessary for continuous evaluation and
repeated tests of different fungicides as
seed soaks and seed treatments to provide
reliable information on the efficacy of
each compound for bakanae disease con-
trol. Hence spore suspensions of the
fungus were sprayed 3 times to the flowers
of IR42 plants at about the flower open-
ing period. The seeds harvested from the
sprayed and unsprayed plants were used
in determining the degree of infestation
using Komada's medium in the laboratory
and bakanae infection on dapog-raised
seedlings in the greenhouse. Spraying
spore suspensions to the plants at flower-
ing stage increased the percentage of
infested seeds and infected seedlings. In
the laboratory the average percentage
increase of infested seeds from the
sprayed plants was more than 7 times.
Similarly, when seeds harvested from the
sprayed plants were grown in dapog beds,
about 17% of the seedlings were infected
by the bakanae fungus compared with
less than 1% of those from the unsprayed
ones. These results indicate that spraying
the plants with spore suspensions during
the flowering stage increase seed infesta-
tion and seedling infection.
Histopathology of rusted grape leaves
and morphological characters of the rust
fungus. R. Villa Juan and A. N. Porde-
simo (BPI-UPLB)
Grape rust is characterized by the pre-
sence of lesions that are pinhead in size
and are cinnamon-brown due to the ure-
dia of the pathogen, located on the neither
surface of the leaf. The lower surface has
severe discoloration from yellowish to
dark necrosis which is an indication of
the presence of the telium. Severely in-


fected leaves dry up prematurely and fall
off. Only uredia and telia of the rust
fungus were found. Uredia are roundish,
subepidermal in origin, erumpent and
measure 2-3 mm x .5-.8mm. Uredospores
are ellipsoid to subspherical, 18 x 14 u,
with echinulate walls. The size of uredos-
pores does not vary with locality. Telia
form lenticular sori which are slowly
dehiscent. They remain long covered by
epidermis and are dark brown to blackish
with chains of 2-7 teleutospores. The
spores are oblong or prismatic in several
spores-deep sub-epidermal crusts with
smooth and colored walls. Uredia and
telia of infected grape leaves in the
Philippines correspond morphologically
and histologically to those of Physopella
vitis as originally described by Arthur in
1906.

Effect of relative humidity on conidial
germination of Helminthosporium oryzae
B. de Haan. A. Obusan, F. L. Nuque, S. P.
Ebron and J. P. Crill (IRRI)

Relative humidities ranging from 13 to
100% at 25C were used to ascertain
which relative humidities conidia will
germinate. Conidia germinated 2 h after
incubation at relative humidities rang-
ing from 86 to 100%. Percentage spore
germination increased with increasing
relative humidity. There was no coni-
dial germination at relative humidites
below 66%, 24 h after incubation.

Fungal diseases of Morado banana
fruits and leaves in Carmen, Davao del
Norte. R. F. Dalisay and A. N. Prodesimo
(UPLB)

Morado banana (musa paradisiaca
glaberrima Blanco), a potential export
commodity, has been found to be
affected by a number of pre-and post-
harvest diseases in Carmen, Davao del
Norte. Foliar and fruit diseases were
observed to reduce fruit yield directly


Vol. 18









Jan. & June 1982


or indirectly and affect the quality and
price of the fruit. The foliar diseases
associated with Morado were Sigatoka
caused by Myscosphaerella musicola
Leach (Cercospora musae Zimm.), and
Cordana leaf spot caused by Cordana
musae Zimm. Diamond black pit, a pre-
harvest fruit disease with which a species
of Cercospora has always been associated,
has also been a serious problem in the
locality. This disease renders the spotted
fruit unattractive. In storage and transit,
fruit rots such as anthrascnose and neck
rot caused by Collectotrichum musae
Berk. et Curt., Botryodiplodia finger rot
caused by Botryodiplodia theobromae
Pat. and crown rot caused by a fungal
complex (C. musae Berk. et Curt, B.
theobromae Pat., and Fusarium moni-
liforme Sheld.) were consistently isolated
and proven to be the causal fungi by
pathogenicity tests. These foliar and fruit
diseases have been noted to occur at vary-
ing intensities in this particular locality.
The two diseases, Sigatoka and Diamond
black pit, have been suspected to
originate from Hijo plantation, Tagum,
Davao del Norte where previous findings
reported their presence in epiphytotic
proportions. Application of fungicides,
sanitation, proper harvesting, handling
packaging, and refrigeration have been
practiced to control these diseases at a
level of minimum fruit loss.

Pathogenic races of Pyricularia oryzae
at IRRI blast nursery. F. L. Nuque, S. P.
Ebron, J. D. Yoo and J. P. Crill (IRRI)

Studies were conducted using two sets
of blast differential to determine the
pathogenic races of P. oryzae and their
frequency of occurrence at IRRI. Forty-
nine isolates were inoculated to the two
sets of differential varieties and the races
were classified based on their reactions to
the varieties. Six races were categorized
based on their reactions to the interna-
tional differentials. The most prevalent


race was IH-1 with 39 (76.6%) isolates
followed by IG-14 (8.2%) and II-13
(6.1%). Races IA-127, IC-19 and IGhave
one isolate with corresponding 2% each,
respectively. Nine races were classified
based on reactions of new Japanese dif-
ferentials. Races 002 (24.5%), 403
(20.4%) and 007 (16.4%) appeared to be
predominant. Races 003 (12.3%) ranked
4th and 006 (10.2%) and 407 (10.2%),
5th, frequency of occurrence. Varieties
Fukinishiki, Yashiro-mochi and Pi No. 4
showed resistant reactions to all the races
identified.

Unreported and/or undescribed fungal
species and genera in the Philippines. T.
H. Quimio, L. E. Abilay, E. A. de Villa
and J. Elauria (UPLB)

Five species of fungi are reported and/
or described for the first time in the
Philippines. These are Gliocephalotri-
chum bulbilium Ellis and Hesseltine from
rambutan fruits, Trichothecium roseum
(Pers.) Link ex Fries from apple, Heli-
comina sp. from grape leaves,Pithomyces
chartarum (Berk. and Curt) Ellis from
peanut leaves and Choanephora cucur-
bitarum (Berk. and Ray.) Thaxter from
jackfruit fruitlets. Except for Helicomina
sp. all have been confirmed to be causing
a disease on their respective hosts.

Wilt disease of coconut in Socorro,
Oriental Mindoro: Etiological studies. R.
G. Abad, E. C. Concibido and R. C.
Norris (PCA)

A fatal wilt disease of coconut was re-
ported in six barangays of Socorro,
Oriental Mindoro. Symptoms include
premature senescence of foliage. Allied
symptoms include premature nutfall,
cessation of reproductive growth and root
rot. Infected palms die within 3 to 7
months from the appearance of the early
symptoms. Inoculation trials on healthy
seedling using diseased tissues (leaves,









Philippine Phytopathology


rachilles, cabbage and roots) produced
negative results. The.same was true for
healthy seedling that were planted in soils
obtained from rhizospheres of infected
palms. Results of pathogenicity tests
involving fungi and bacterium isolated
from infected coconuts and nematodes
from within the rhizospheres of diseased
palms were also negative. In addition,
polyacrylamide gel electrophoresis dis-
counted the implication of viroid, and
apparently virus, as possible causal agent.
Apart from this, initial electron micros-
copy of tissue samples from infected
palms did not show presence of other
possibly associated microorganisms
(mycoplasma or uniflagellate protozoa)
but works on this and etiological studies
are still continuing. Meanwhile, in view of
the economic importance of the disease,
quarantine measures have already been
undertaken and screening of coconut
populations (coming from various parts
of the country) for disease resistance is
already on-going.

Resistance to rice tungro A case of
IR34 variety. R.C. Cabunagan and K. C.
Ling (IRRI)

Studies were conducted to determine
the mechanism and stability of resistance
of IR34 against rice tungro. Rearing green
leafhoppers, Nephotettix virescens on
IR34 for 9 generations resulted to a pro-
gressive increase in the life span and trans-
mission of rice tungro virus. A gradual
increase in the adaptability of the colony
on IR34 as shown by the change in the
life span resulted also to a gradual in-
crease in the RTV transmission with the
advancing generation. It is evident that
the rice tungro resistance of IR 34 is in-
fluenced by its resistance to the vector. In
addition, this also indicates how unstable
the resistance of a variety to tungro when
its resistance is only due to the vector.


Phytotoxicity of filtrates from
cultures of Colletotrichum lindemu-
thianum causing anthracnose of stylo
(Stylosanthes suyanensis). C. K. Alagad,
Jr. and J. D. Revilla (CLSU)

Filtrates from cultures of Colleto-
trichum lindemuthianum in Richard's
medium exhibited toxic effects when
bioassayed for activity. Cut seedling of
stylo variety Schoefield dipped in con-
centrated filtrates ( dilutions 10-1, 10-2)
wilted after two days of incubation.
Anthracnose symptom appeared _n the
leaves at dilutions 10"3 to 10 The
symptoms induced by the toxin at higher
dilution (10-3 to 10"i ) Uupicated those
of stylo plants infected by the pathogen.
The severity of the symptom decreased
as the dilution was increased. The toxin
was non-host specific, Wilting, spotting
and/or yellowing were induced on a
variety of legumes which included mung
bean, lima bean, soybean, snap bean,
string bean, hyacinth bean, cowpea
and winged bean.

Tetep: A potential source of resistance
to rice dwarf in Nepal. B.P. Upadhyay
and D. B. Lapis (IRRI)

A preliminary screening of varieties was
done in the greenhouse in Khumaltar,
Nepal in 1981. The technique of Jones et
al., 1979 was used to establish the virus
in the test plants. Out of 44 entries
tested, only seven entries, namely: IR20,
IR2071-625-1, IR3707-117-2, IR27997-
125, Tetep, IR1416-128-5-8, IRI905-81-
3-1 were highly resistant (0-5% of seed-
lings infected). Cultivars IET 2938,
IRI544-340-6-1 and IR1905-P11-29-4-1
were resistant (6-20% of seedlings in-
fected). All other cultivars showed sus-
ceptibility to rice dwarf virus in different
degrees ranging from moderate to high.
The resistance found in Tetep and Tetep-
drived lines, namely; IR1416-128-5-8,
IR1905-81-3-1, IR1544-340-6-1 and


Vol. 18









Jan. & June 1982


IR1905-P11-294-1 is of particular
significance to Nepal because blast is the
only disease causing severe yield-loss in
this locality and Tetep or Tetep-derived
improved lines are the sources that are
most commonly used in incorporating
blast resistance.

Assessment of yeild losses due to
bacterial spot and gray leaf spot of
tomato. M. V. T. Neypes and R. B.
Valdez (UPLB)

Yield losses on tomato bacterial (Xan-
thomanas vesicatoria) and gray leaf spot
(Stemphylium lycopersici) were studied
in pot experiment at three stages of
inoculation, namely, 4, 6 and 8 weeks
after seedling emergence. Losses due to
bacterial spot were 46.7%, 37.7% and
29.3% respectively in the dry season and
59.7%, 29.1%, and 19.2/ respectively, in
the wet season. Those due to gray leaf
spot were 31.3%, 28.8%, and 8.5% in
the dry season and 55.7%, 51.1%, and
33.8% in the wet season. Bacterial spot
on fruits further reduced fruit quality.

Seedling infection by ragged stunt
using the masss screening method at three
inoculation access time. R. D. Daquioag,
V. M. Aguiero and K. C. Ling (IRRI)

Following the mass screening method
for testing varietal resistance to RRSV
(IRRI, 1979), 29 rice seedlings were
transplanted per pot. Sixteen pots of test
seedlings were exposed to about 3,500
viruliferous BPH in a cage. Two inocula-
tion cages were used; one for the 8- and
16 h IAT from 0800 to 1600 hr, and
respectively and the 24-hour IAT from
0800 to 0800 hr of the following day.
Results indicated that the capaicty of the
mass screening method can be doubled,
however, the percentage of seedlings in-
fection may be increased by adding more
viruliferous insects per cage. When
seedlings of four rice varieties were tested


by the mass screening method using the
8-and 16- and 24-h inoculation
schedules, the average percentage infec-
tion of TN1 was more than 88; IR42 and
IR26, more than 61; and Ptb 21, about
14. Results indicated that the varietal
reactions to RRSV was similar using the
three inoculation access times.

Cucumber mosaic virus and potato
virus Y: Unreported viruses of tabacco
(Nicotiana tabacum L.) in the Philippines.
(L. A. Revellame and D. A. Benigno
(PTRTC-UPLB).

Cucumber mosaic virus (CMV) and
potato virus Y (PVY) were isolated from
naturally infected tobacco leaf samples
collected from Ilocos Norte, Ilocos Sur,
Abra, La Union, Pangasinan, Cagayan
Isabela, and Occidental Mindoro in 1980-
81 cropping season. These viruses were
identified through indicator hosts
reaction, physical properties, serology
and electron microscopy. CMV isolate
induced systemic mosaic, and chlorosis
on Nicotiana glutinosa L, and N. taba-
cum L. White Burley; mild systemic
symptoms on Cucumis sativus L. (var.
Pixie) and necrotic local lesions in Cheno-
podium amaranticolor Coste et Reyn.
Its physical properties were DEP =
10"4; TIP = 65 C and LIV = 4 days. It
reacted strongly to CMV-Y anti-serum
in agar-gel immunodiffusion test. The
PVY isolate did not infect D. stramo-
nium; produced mild mottling symptoms
in N. glutinosa, N. tabacum and D. metel,
and necrotic and chlorotic local lesions
were produced in Solanum tuberosum
(hybrid 'A6') and C. amaranticolor
respectively. The virus had a DEP of 10"3,
TIP was 55-60, C, LIV of 2 days, and
flexous rod particles of about 730-790
nm. It reacted positively to PVY antiserum
in ELISA test and immunodiffusion test
in agar-gel. Field symptoms on tabacco
include chlorosis, mottling, leaf mal-
formation and stunting and mottling









Philippine Phytopathology


with vein-banding for CMV and PVY,
respectively.

Effect of acquisition and inoculation
access time on rice ragged stunt virus
transmission. V. M. Aguiero, R. D.
Daquioag and K. C. Ling (IRRI).

Two thousand eight hundred one
virus-free second instar BPH nymphs were
given different acquisition access times
(AAT) and then immediately allowed to
inoculate TN1 seedlings for one day. To
obtain virus-free BPH, gravid females
were confined in screen cages with Mono-
choria vaginalis for egg laying. Healthy
TN1 seedlings were placed inside these
cages 5-6 days after insects' confinement
to serve as food for the nymphs that
would emerge. Only those that had an
acquisition feeding of 24 h or longer be-
came infective. The positive transmission
results of 24-h AAT and 24-h inocu-
lation access time indicated that the
shortest latent period of RRSV in the
vector could be at maximum of 48 .h.
Furthermore, the longer the acquisition
access time, the higher was the percentage
of infective insects. Daily serial transmis-
sion tests until the insects' death showed
positive transmission with acquisition
access times of 10, 15, 30 and 60 minutes
indicating short acquisition assess time
for virus transmission. Inoculation feed-
ing after an acquisition feeding of 10
days on diseased plants showed positive
transmission as early as 5 minutes or
longer. However, the transmission in
terms of percentage of infective insects
increased as the inoculation access time
lengthened.

Carbofuran improved sugarcane
ratooning. R. J. Serra, F. T. Gargantiel
and F. C. Barredo (VICMICO).

The application of carforuan 3G at 2
kg a.i/ha has improved yield by 27, 24,
and 54 piculs sugar per hectare over the


control in the plant, first ratoon and
second ratoon stages, respectively. The
treated field was observed to have more
millable stalks than the control which
consequently effected a higher tonnage.
This was the main factor that brought
about the increased picul sugar yield per
hectare in all stages. The nematode popu-
lation was likewise affected by the appli-
cation of the chemical. Though popu-
lation started to increase in later stages,
the damage must have been tolerated
due to the well established root system.
The application proved to be economical-
ly feasible.

Evaluation of soil sampling techniques
for plant parasitic nematodes on sugar-
cane. R.J. Serra and T. T. Reyes
(VICMICO-UPLB)

Four sampling techniques were com-
pared to determine their relative ef-
fiency in estimating nematode popula-
tion on sugarcane. The Barlett's and F -
Tests showed significant differences only
with the two sets of comparison: between
the stratified systematic sampling and
the stratified ramdom sampling, and
between the stratified systematic
sampling and the systematic sampling.
Though the stratified systematic sampling
was not statistically significant compared
to simple random sampling, the relative
efficiency analysis proved that the most
appropriate and most efficient.

Field evaluation of Ridomil MZ 58 WP
and Ridomil MZ 72 WP against potato
late blight.. J. S. Mariano, M. J. Ferrer
and Munoz (BPI)

Ridomil MZ 58 WP, a combination of
10% acylalanine and 48% mancozeb and
Ridomil MZ 72 WP, a 20% acylalanine
and 52% mancozeb were evaluated for
the control of late blight of potato in
farmer's field at Paoay, Atok from May-
August 1981. Ridomil MZ 58 WP and


Vol. 18









Jan. & June 1982 21


Ridomil MZ 72 WP sprayed at the rate of
66.6 83.3 and 100 grams per 20 liters of
water applied at 7 and 10 day intervals
satisfactorily controlled late blight and
gave highly significant increase in yield
over the standard fungicides used.










Philipp. Phytopathol. 18: 22-33


INTERRELATIONSHIP OF RADOPHOLUS SIMILIS AND
(MELOIDOGYNE INCOGNITA IN BANANA

W. SANTOR and R. G. DAVIDE

Respectively, former graduate student of Nematology and Professor of Plant
Pathology, College of Agriculture, University of the Philippines at Los Banos, College,
Laguna, Philippines.

ABSTRACT
The interrelationships of R. similis and M. incognita inoculated to three cultivars
of banana (Saba, Bungulan and Giant Cavendish) were studied using three inoculum
levels of 1,000, 5,000 and 10,000 nematode individuals per plant. Results revealed that
the three cultivars were susceptible to infection by both species. Plants inoculated with
R1 similis alone showed typical root lesion symptoms, while those inoculated with M.
incognita developed root galls. Both lesions and galls developed in plants jointly ino-
culated by both species. Lesions were also observed in the galled portions of the roots
indicating R. similis infection.
Number of lesions observed was higher in roots of plants inoculated singly with
R. similis and likewise more galls were found in roots of plants inoculated with M.
incognita alone than those jointly inoculated by both species. Generally, the higher the
inoculum level the greater the number of lesions and galls developed when each species
was inoculated singly into the banana plants. However, when both species were jointly
inoculated there was a reduction in the nematode population and the formation of
lesions and galls indicating that the two species were affecting each other. Histo-
pathological study of the galled roots with lesions showed that the presence of R.
similis in the galled tissues had affected the development and reproduction of M.
incognita as majority of them did not develop beyond the second larval stage and
very few reached the adult female stage. The R. similis infection on the galls caused
deterioration and disintegration of the giant cells, a condition which adversely af-
fected the feeding cites and development ofM. incognita.


INTRODUCTION

Banana is the most widely planted
fruit crop in the Philippines covering
about 300,000 hectares, principally
located in Southern and Northern Min-
danao, and Southern Tagalog (Radan,
1978). This ranks the Philippines third in
international standing in terms of banana
production, behind only Ecuador and
Costa Rica (Adam, 1978).
The banana industry, however, is
being threatened by nematode pests
particularly Meloidogyne incognita Chit-
wood and Radopholus similis Cobb which
are causing serious damage on some
banana cultivars (Davide and Gargantiel,
1974). Davide (1974) observed that the
population density of M. incognita is
affected by R. similis in older banana


plantations indicating the existence of an
antagonistic effect of R. similis on the
reproduction ofM. incognita.
This paper reports on the findings
of the following studies: 1) influence of
three cultivars of banana on the repro-
duction of R. similis and M. incognita,
when inoculated singly or in combina-
tion, 2) effects of R. similis on M. in-
cognita at different population levels,
and 3) effects of R. similis infection on
the formation of galls and giant cells by
M. incognita in the infected roots of
banana.

MATERIALS AND METHODS

Two experiments were conducted
under greenhouse conditions. M.
incognita was cultured in susceptible









Interrelationship of R. similis and M. incognita


tomato plants (var. VC-11-1) starting
from a single egg mass. R. similis was
isolated from infected roots of Cavendish
banana gathered from Hijo plantation,
Davao del Norte. Three banana cultivars,
namely; Giant Cavendish, Saba, and
Bungulan were used as test plants. They
were chosen on the basis of their econo-
mic importance, susceptibility to the
nematodes and differences in genetic
make-up. Genetically both Bungulan and
Giant Cavendish are Musa AAA type
while Saba is Musa ABB.
Experiment I The three selected
varieties of banana (Giant Cavendish,
Saba and Bungulan) were separately
planted in 30 cm clay pots filled with
sterilized soil. Two months after planting,
each plant was inoculated with both R.
similis and M. incognita. Larvae and
adults of R. similis and newly hatched
larvae of M. incognita were used as in-
oculum at 1,000, 5,000 and 10,000 levels
and replicated fi4e times for each variety
in a completely randomized design. Con-
trols were provided for each variety
where plants were inoculated separately
with R. similis and M. incognita. Five
plants in each variety were not inoculated
to provide healthy controls. Three
months after inoculation, the plants were
carefully uprooted and washed with tap
water. Root samples from each treatment
of each variety were collected and placed
separately in plastic bags. Five-gram root
samples from each treatment were taken
and fixed in FAA. Histopathological
studies were made on root galls with and
without R. similis lesions to determine
the effect of R. similis infection on the
formation of giant cells and growth of
M. incognita inside the galls.
To determine the number of R.
similis present in the root system, 5-g
root samples were taken, chopped into
1 cm length, placed in 100 ml water and
macerated in a waring blendor for a few
seconds. The resulting suspension was
then poured onto a tissue paper
supported by a wire screen on a


Baermann funnel to remove plant debris
and the nematodes were drawn from it
within 2448 hours. They were then
counted in a calibrated watch glass under
a stereo microscope. For plants infected
with M. incognita alone and those with
R. similis and M. incognita combinations,
5-g root samples were taken from each
treatment and stained in boiling acid-
fuchsin lactophenol for 3-4 minutes. All
stained roots were stored separately in
vials containing plain lactophenol. The
nematodes were counted by dissecting
the roots in a watch glass under the stereo
microscope. To determine the nematode
population in the soil, 400 cc soil samples
from each pot were taken and screened
through No. 50,200 and 325 mesh sieves.
The suspensions left in No. 200 & 325
were poured into the Baermann funnels
where the nematodes were drawn out 48
h later.
Experiment II. In this experiment
only the commercial Cavendish variety
was used as test plants and were planted
as in experiment I. Two treatments were
included. The first one involved the in-
oculation of the plants with M. incognita.
They were allowed to establish and form
root galls. Three weeks later the same
plants were inoculated with R. similis.
The inoculum levels used were 1,000,
5,000 and 10,000 per plant. Each treat-
ment has 5 replications in a complete-
ly randomized design. Controls were pro-
vided for each inoculum level where only
M. incognita was introduced.
The second treatment involved the
inoculation of R. similis first and 3 weeks
later M. incognita was inoculated into the
same plants. The same level of inoculum
were used. The control plants involved
were inoculated only with R. similis.
After three months the root systems of
all plants were removed and washed with
tap water. The cleaned roots were
collected in separate plastic bags and
brought to the laboratory for nematode
analysis. Five-gram root samples from
each treatment were fixed in FAA and


Jan. & June 1982









Philippine Phytopathology


later were stained in boiling acid-fuchsin
lactophenol for 3-4 minutes. After wash-
ing the excessive stain in water the roots
were stored in separate vials containing
clear lactophenol. Later the nematodes
from these stained roots were dissected
and counted under a stereo microscope.
Soil samples of 400 cc from each treat-
ment were taken to determine the soil
population of the nematodes using the
same method of extraction described in
Experiment I.

RESULTS

Varietal reaction. All the three
cultivars tested (Giant Cavendish, Saba
and Bungulan) showed susceptible in-
fections-to R. similis and M. incognita.
Plants inoculated with different inoculum
levels of R. similis alone showed typical
root lesion symptoms, while roots in-
oculated with M. incognita alone de-
veloped galls. When plants were inocu-
lated with both nematode species
symptoms of lesion and galling of roots
were observed. Lesions were also
observed in the galled portion of the
roots.
Number of lesions in plants in-
oculated with R. similis alone was higher
than those inoculated with both nema-
tode species. A significant difference in
the number of lesions was observed at the
5,000 and 10,000 inoculum levels for
Saba and Bungulan cultivars whereas
Giant Cavendish lesion count was signi-
ficant only at the 10,000 level. Similarly,
the number of galls was higher in plants
inoculated with M. incognita alone than
those inoculated with both species. Saba
showed a significant difference in the
number of galls at the 10,000 level,
Bungulan at the 5,000 and 10,000 levels
while Giant Cavendish had a significant
difference in all levels of inoculum (Table
1). Significant differences among nema-
tode counts were found within the three
inoculum levels of R. similis and M.
incognita either inoculated alone or com-


bined. Highest nematode count was
obtained from plants inoculated initially
with 10,000 larvae of R. similis alone.
Saba had a count of 1312.4 while Bungu-
lan and Giant Cavendish had 1562.0 and
1590.4, respectively (Table 2). Saba
and Bungulan have significant population
reduction of R. similis when both species
were inoculated together at the 5,000 and
10,000 inoculum levels while in Giant
Cavendish a significant reduction at
1,000, 5,000 and 10,000 inoculum levels
was observed.
Population of M. incognita re-
covered from 5-g root sample was also
found to be higher in plants inoculated
with it alone than those inoculated joint-
ly with R. similis. Population counts were
highest in plants inoculated with 10,000
M. incognita larvae. M. incognita count
in Saba was 316.8 while Bungulan and
Giant Cavendish had 982.0 and 442.6
respectively (Table 2). Significant re-
duction of M. incognita population was
obtained in all inoculum levels in the
presence of R. similis in Giant Cavendish
and Bungulan, whereas in Saba a signifi-
cant reduction was only observed at
10,000 inoculum level.
The soil count of R. similis and M.
incognita recovered from plants in-
oculated with R. similis alone, M. in-
cognita alone, and R. similis + M. in-
cognita also showed some variations.
Generally at high inoculum level, there
were more nematodes in the soil which
may mean that there were not enough
infection sites in the roots available for
them (Table 3).
Varying the periods of the joint
inoculation of both species. When
M. incognita was allowed first to infect
and develop in the test plants, followed
by inoculation with R. similis 3 weeks
later the .population count of M. in-
cognita on 5-g root sample was higher
than those where R. similis was allowed
to infect and develop first and 3 weeks
later inoculated with M. incognita (Table
4). When inoculated ahead of R. similis,


VoL 18







Table 1. Single combined effects of Radopholus similis and Meloidogyne incognita on lesion and gall
development at three inoculum levels on the susceptible banana cultivars.


Banana Cultivar & No. of Lesions and Galls
TREATMENT Inoculum Saba Bungulan G. Cavendish
Level Lesion Galls Lesion Galls Lesion Galls

Radopholus + 1,000 + 1,000 33.8 12.4 36.8 23.4 44.5 6.0*
Meloidogyne 5,000 + 5,000 32.6* 20.8 29.8** 12.6** 38.6 7.6*
10,000 + 10,000 40.6* 13.2** 49.8** 10.0** 37.0** 13.8**
Radopholus 1,000 44.6 52.0 66.0
alone 5,000 63.2* 69.4** 64.8 -
10,000 97.4* 106.8** 102.4*** -
Meloidogyne 1,000 20.4 38.6 44.6*
alone 5,000 43.0 58.8** 54.2*
10,000 77.0** 83.0** 71.2**

Lesions Galls
LSD .05 29.1 32.2
.01 38.7 42.8

*Significant at 5% probability level, ** significant at 1% when comparing the number of galls and lesions that
developed in combined inoculation and single inoculation with R. similis or M. incognita at the same level of inoculum.









Table 2. Population counts of Radopholus similis and Meloidogyne incognita from 5-g root samples from three
banana cultivars inoculated with Radopholus alone, Meloidogyne alone, and Radopholus tMeloidogyne
combinations.

BANANA CULTIVAR & NEMATODE COUNTSa
Inoculum
TREATMENT Level Saba Bungulan Giant Cavendish
R. similis M. incognita R. similis M. incognita R. similis M. incognita

R. similis + 1,000 + 1,000 133.8* 77.8 121.6 148.6* 110.8* 25.2**
M. incognita 5,000 + 5,000 63.8** 104.4 37.8 41.4* 114.8* 71.2**
10,000 + 10,000 96.8** 65.6** 158.4** 117.6** 94.6** 118.9**
R. similis 1,000 204.6* 262.0 472.8* -
alone 5,000 390.2** 387.4** 408.4* -
10,000 1321.4** 1562.0** 1590.4**
M. incognita 1,000 107.8 493.0* 378.8**
alone 5,000 157.8 220.0* 217.6**
10,000 316.8** 982.0** 442.6***


aData represent mean of 5 replicate plants. = Significant at 5% level, ** = Significant at 1% level based on the transformed data
analyzed using LSD when comparing the means of the combined species treatment with the single species treatment at corresponding
levels of inoculum.







Table 3. Population counts of Radopholus similis and Meloidgyne incognita in 400 cc soil samples from three banana
cultivars inoculated with R. similis alone,M. incognita alone, and R. similis + M. incognita.


BANANA CULTIVAR & NEMATODE COUNTS1
Inoculum Saba Bungulan Giant Cavendish
TREATMENT Level R. similis M. incognita R. similis M. incognita R. similis M. incognita

R. similis + 1,000 + 1,000 50.6 36.8** 163.8** 187.8** 98.0 79.4**
M. incognita 5,000 + 5,000 138.4** 296.0* 49.6 75.8** 101.4 140.2
10,000+ 10,000 37.6** 61.2** 15.6** 65.4** 47.8* 260.4*
R. similis 1,000 55.6 37.8** 1 108.8 -
alone 5,000 87.4** 75.2 92.0
10,000 122.4** 179.6** 115.6 -
M. Incognita 1,000 123.4** 124.2* 250.8**
alone 5,000 178.6* 151.4** 197.6
10,000 146.4** 186.8** 163.0*


1Data represent mean of replicate plants. = Significant at 5% level, ** = Significant at 1% level based on the transformed data
analyzed using LSD when comparing the means of the combined species treatment with the single species treatment at corresponding
levels of inoculum.









Table 4. Population counts of R. similis and M. incognita from 5-g root samples of Giant Cavendish ino-
culated with R. similis first and M. incognita later, and M. incognita first followed by R. similis
3 weeks later.


TREATMENT


R. similis followed
by M. incognita




M. incognita followed
by R. similis


Inoculum
Level


1,000

5,000

10,000

1,000

5,000

10,000


LSD .05

LSD .01

cv%


NEMATODE COUNTS PER 5-g ROOTS a
R. similis M. incognita

144.0 (2.082) 21.6 (1.207)**

304.8 (2.374) 55.8 (1.503)**

620.8 (2.655) 117.6 (2.010)**

185.4 (1.907) 236.4 (2.202)

275.2 (2.055) 315.2 (2.417)

337.4 (2.131) 867.2 (2.843)

ns (0.55)

ns (0.76)


4.05 1.45


aData represent mean of 5 replicate plants. ** = Significant at LSD .01; ns = not significant. Data in parentheses are
computed log transformed values to reduce the coefficient of variation.









Interrelationship of R. similis and M. incognita


M. incognita was able to establish and
form root galls. On the other hand, R.
similis, still initiated lesions in the galled
portion of the roots even when in-
oculated later, indicating feeding action
of R. similis on the galled tissues.
When M. incognita was inoculated
3 weeks after inoculation with R. similis,
the number of galls was significantly
reduced in all inoculum levels. The galls
were only found in areas where there
were no R. similis lesions.
On the other hand, the population
counts of R. similis in 5-root sample did
not vary whether inoculated first with R.
similis or after inoculation with M. in-
cognita. The same trend of results was
observed in the soil (400 cc sample)
population counts of the nematodes
(Table 5).
Less number of M. incognita de-
veloped into adult females in plants in-
oculated with R. similis (Table 6). In the
presence of R. similis majority of M.
incognita did not develop beyond the
advanced second larval stage.
Histopathological study of galled
roots. Microtome sections of galled
roots with R. similis lesions indicate the
interaction of the two nematode species
at the cellular level. R. similis was never
observed to be directly in contact with
M. incornita. No R. similis have been
found inside the adult body of M. in-
cognita females. They were usually found
about two or three cells away from each
other (Fig. 1). The cells surrounding the
giant cells are highly stained dark red
showing the necrotic effect of R. similis.
The walls of giant cells appeared necrotic
and disintegrating in some cases. Normal
giant cells stained dark green were thick
walled with dense cytoplasm and multi-
nucleate (Fig. 1), whereas giant cells
in the presence of R. similis appeared
necrotic


DISCUSSION

Higher population counts of R.
similis and M. incognita were obtained
from plants inoculated separately than
those of the combination of both species.
The reduction in the population density
of both R. similis and M. incognita when
jointly inoculated into the test plants in-
dicates that both nematodes mutually
affect each other's reproductive capacity.
Similarly, O'Bannon et al. (1976) ob-
served that combined population of R.
similis and Pratylenchus coffeae or cit-
rus were much lower than those where
each species was present alone. They
thought that there were inhibitory effects
which could be a combination of compe-
tition for feeding sites and reaction of
compounds in plants which may be toxic
to the nematodes. In this study, the in-
hibitory effect of R. similis on M. in-
cognita in banana appeared primarily to
be competition for feeding sites and the
necrosis reaction of the R. similis-in-
fected root tissues which M. incognita
could no longer utilize as infection
sites. The presence of R. similis in the
vicinity of giant cells indicates that
R. similis was not affected by M. in-
cognita. On the other hand, M. in-
cognita was affected by the presence
of R. similis because of its destructive
effects on the giant cells as shown by the
formation of necrosis on the affected
cells.
The population ofM. incognita was
affected when R. similis was inoculated 3
weeks ahead. Evidently R. similis des-
troyed the root system as a result of its
feeding action and M. incognita fails to
infect and survive on these dead tissues of
R. similis-infected roots. A similar
observation was reported by Sikora and
Scholosses (1973) on the antagonistic
effect of Helicotylenchus nulticinctus on
M. incognita, while Estores and Tseh
(1972) noted an inhibitory effect of
Pratylenchus penetrans on M. incognita.


Jan. & June 1982








Table 5. Population counts of R. similis and M. incognita in 400 cc soil samples from Giant Cavendish
inoculated with R. similis first and M. incognita later, and M. incognita first followed by R.
similis 3 weeks later.

Inoculum NEMATODE COUNT PER 400 cc SOIL SAMPLE a
TREATMENT Level
R. similis M. incognita

R. similis followed
by M. incognita 1,000 46.6 (1.658)ns 116.6 (2.011)

5,000 59.2 (1.759)** 132.0 (2.107)

10,000 38.8 (1.544)ns 73.4 (1.855)

M. incognita followed
by R. similis 1,000 65.2 (1.754) 245.2 (2.192)

5,000 17.0 (1.222) 109.0 (2.031)

10,000 45.4 (1.633) 86.4 (1.933)

LSD .05 (0.214) ns

LSD .01 (0.392) ns

cv% 0.27 0.37

aData represent mean of 5 replicate plants. ** = Significant at LSD .01; ns = not significant. Data in parentheses
are computed log transformed values to reduce the coefficient of variation.







Table 6. Meloidogyne incognita in different stages of development recovered from 5-g root samples of Saba, Bungulan and Giant
Cavendish banana inoculated with M. incognita alone, and M. incognita + R. similis.

BANANA CULTIVAR & NEMATODE COUNTS1
Inoculum Saba Bungulan Giant Cavendish
TREATMENT Level Larval Stages Adult Larval Stages Adult Larval Stages Adult

2nd 34th Female 2nd 3-4th Female 2nd 3-4th Female

M. incognita alone 1,000 67.6 20.4 19.8 415.8 35.2 42.0 273.0 39.2 66.6

5,000 68.0 42.8 43.8 79.0 71.0 70.2 97.4 81.2 39.0

10,000 163.2 108.2 45.4 755.2 137.6 89.2 218.8 93.4 130.4

M. incognita +
R. similias 1,000 + 1,000 55.4 6.4 16.0 92.2 28.2 28.2 28.2 0.6 1.8

5,000 + 5,000 62.6 17.2 24.6 19.2 13.4 8.8 67.8 1.2 2.2

10,000 + 10,000 45.6 10.0 10.0 105.8 4.2 7.6 98.8 12.8 7.0

aData are means of 5 replicate plants.


t



0o
i
8









Philippine Phytopathology


The presence of R. similis also af-
affected growth and development of M.
incognita. The larval stages, especially the
third and fourth stages, and the adult egg-
laying stage were greatly affected in
plants inoculated by both species.
Majority of M. incognita did not develop
beyond the second larval stage. Only few
adult females reached the egg-laying stage
(Table 6). In tissue sections of galled
roots with R. similis lesions the giant cells
appeared necrotic with cytoplasm and
nuclei in process of deterioration (Fig.
1). Similar observation was also shown
by Schmidt and Lewis (1981) on the
effect of Hoplolaimus columbus on M.


incognita giant cells of cotton. Accord-
ing to them these necrosis of the tissues
may be due to the release of phenolic
compounds as a result of feeding action
of the nematodes. Evidently, in nature,
the population of M. incognita can easily
be affected if other nematode species
feeding on the same sites of the host
tissues change the physiology of the giant
cells like the production of necrosis and
inhibition of the formation and develop-
ment of these giant cells. Under this situa-
tion M. incognita and other gall forming
species become poor competitors and
have a lower chance of survival than R.
similis and other lesion forming species.


Vol. 18









Interrelationship of R. similis and M. incognita


LITERATURE CITED

ADAM, L. 1978. Bananas are still tops. Farming Today. 4.(4): 17-19.

COLBRAN, R. C. and G. W. SAUNDERS. 1961. Nematode root-rot of bananas. Quens-
land Agr. Jour. 87(1): 22-24.

DAVIDE, R. G. 1974. The association of plant parasitic nematodes with banana. A
portion of the NSDB research project No. 7314 Ag. Annual Report. March 1974.
85 p.

DAVIDE, R. G. and F. T. GARGANTIEL. 1974. Survey and identification of plant
parasitic nematodes associated with banana. Phil. Phytopathol. 10(1 & 2): 1-2.

DAVIDE, R. G. 1980. Influence of cultivar, age, soil texture, and pH on Meloidogyne
incognita and Radopholus similis on banana. Plant Disease 64: 517-573.

ESTORES, R. A. and A. C. TSEH. 1972. Interactions of Pratylenchus penetrans and
Meloidogyne incognita as coinhabitants in tomato. J. Nematol. 4:170-174.

O'BANNON, J. H., J.D. RADEWALD, A. T. TOMERLIN and R. N. INSERRA. 1976.
Comparative influence of Radopholus similis and Pratylenchus coffeae on citrus.
J. Nematol. 8: 58-63.

RADAN, R.R. 1978. Bananas. Greenfields 8(9): 18-22.

SCHMIDT, H. K. and S. A. LEWIS. 1981. Dynamics of concomitant populations of
Hiplolaimus columbus, Scutcllonema brachyurum, and Meloidogyne incognita on
cotton J. Nematol. 13: 14-47.

SIKORA, R. A. and E. SCHLOSSES. 1973. Nematodes and fungi associated with root
systems of banana in a state of decline in Lebanon. Plant Dis. Reptr. 57: 7,615-618.


Jan. & June 1982









Philipp. Phytopathol. 18: 34-42


DAMPING-OFF DISEASE OF TOBACCO: OCCURRENCE,
DISTRIBUTION, AND SCREENING FOR
RESISTANCE

P. N. DIPON and R. G. DAVIDE

Respectively, former graduate student, now Research Specialist at Philippine
Tobacco Research & Training Center, Batac, Ilocos Norte and Professor of Plant Patho-
logy, College of Agriculture, University of the Philippines at Los Banos, Colloge,
Laguna.
Portion of M.S. Thesis UPLB, Nov. 1981.

ABSTRACT
Four of the five pathogens reportedly causing damping-off of tobacco were
isolated by the baiting technique and through the use of selective media from 135
samples collected from seven tobacco-growing provinces in Northern Luzon, namely:
Ilocos Norte, Ilocos Sur, La Union, Pangasinan, Cagayan, and Isabela. The pathogens
isolated were Pythium sp., Fusarium oxysporum f. nicotianae, Rhizoctonia solani
and Sclerotium rolfsii. Phythopthora parasitica var. nicotianae was not detected.
Pythium sp. and F. oxysporum f. nicotianae were the most common and present in all
samples. R. solani and S. rolfsii occurred very rarely and were not present in the
samples collected from the provinces of Cagayan and Abra, respectively.
Introduction test on tobacco var. Golden Harvest showed Pythium sp. the most
virulent followed by F. oxysporum f. nicotianae, R. solani and S. roflsii.
Resistance of tobacco to the four pathogens was observed mainly in the Virginia
types. All of the filler and wrapper types were highly susceptible. Coker 139 and Dixie
Bright 102 were resistant to S. rolfsii, while Buyers Choice, Coker 411, Coker 136,
Oxford 26, Yarda, and 100 Leaves were moderately resistant. Coker 411, Coker 139,
and Dixie Bright 102 were resistant to F. oxysporum f. nicotianae, while Coker 136
and Reams 66 were moderately resistant. Virginia 21 was resistant to R. solani, where-
as Coker 411, NCBY, and Harrison Special were moderately resistant. However, NCBY,
Coker 139, and Dixie Bright 102 were only moderately resistant to Pythium sp.
Varieties resistant to one or two of the four pathogens became susceptible
when exposed to the mixture of these pathgens. Apparently, there was a synergistic
association of these pathogens resulting in more severe disease development.


INTRODUCTION

Seedbedding is an important part of
tobacco culture, and teh stand of the
seedlings in the seedbeds is a critical
factor. Seedlings infected with damping-
off usually do not recover. Once infection
affects small area of the seedbed, the
whole area is subsequently wiped out in
a relatively short time. Infection can
occur before the seedling emerges or at
any stage of the development of the


seedlings.
The monoculture of tobacco over
an extensive area and constant watering
of the seedbed provide ideal environment
for damping-off pathogens.
There had been several reports on
the organisms causing damping-off of
tobacco. In the Philippines, the disease is
either caused by Fusarium sp., Pythium
debaryanum Hesse, Phythopthora para-
sitica (Dast) var. nicotianae (Breda de
Haan) Tucker, or Rhizoctonia solani









Damping-off disease of tobacco


Sacc. (Clara, 1925; David and Roldan,
1926).
The use of resistant varieties in
controlling plant diseases can not be
overemphasized. There are several cases
to prove that resistant variety is an ans-
wer to the problem where pesticides
and other control measures fail.
One factor that determines the
success of breeding for disease resistance
is the availability of sources of resistance.
Resistant genes may be present either
in available variety, or resistant plants
from wild type species (Dalmacio, 1979).
Detection of these sources of resistance
in plants may be done through the use
of adequate screening procedures.
The study was aimed to determine
which of the different organisms causing
damping-off of tobacco is the most
prevalent and widely distributed in the
different tobacco growing areas in North-
ern Luzon and to screen different toba-
cco varieties for resistance to the diffe-
rent organisms causing damping-off.

MATERIALS AND METHODS

Survey and Collection of
Soil Sample

A survey of damping-off incidence
was conducted in seven provinces in
Northern Luzon, namely: Ilocos Norte,
Ilocos Sur, La Union, Pangasinan, Abra,
Cagayan and Isabela. It was done at the
beginning of the planting season in these
areas.
Five 5-cc soil samples were collect-
ed from seedbeds planted to tobacco
where chemical was not frequently
applied. Collection was done at random
and soil samples from each location
were placed in plastic bags and labelled.


Occurrence and Distribution

To determine the occurrence and
distribution of the pathogens, isolation
of the organisms was done direct from
the soil using selective media or by the
baiting technique.

Pythium sp.
Sorghum seeds were boiled for
about 10 minutes then halved with the
blade. Aliqouts of soil sample were placed
in sterile petri dishes, distilled water was
added, and about four halved sorghum
seeds were placed. The plates were incu-
bated and examined until mycellium
appeared surrounding the baits.
Colonized baits were washed in
running water and transferred to fresh
sterile distilled water. Using a dissecting
microscope hyphal filaments were cut
with sharp blade and planted on water
agar. A piece of the agar with the mycel-
lium was cut and transferred to new agar
plates for further examination. Pure
culture of the organisms was obtained
by plating water agar block with the
mycellium on PDA.

Fusarium oxysporum f. nicotianae
Nash medium (Nash and Snyder,
1962) consisting of 1.5% Difco peptone;
2%agar, 0.1% KH2PO4, 0.05% MgSo4.
7H20, 300 ppm streptomycin, and
1:1000 PCNB, was used. Plate was
poured with the melted medium and
incubated for 3 to 4 days before inocula-
tion. A 1:1000 soil dilution using 0.01%
agar as diluent was made and used to
inoculate the plate. Inoculated plates
were then incubated and observed for
colony growth of Fusarium.

Rhizoctonia solani
Selective medium of Herr (1973)


Jan. & June 1982









Philippine Phytopathology


was used. Paper assay disks (0.5 cm
diameter) were made from Whatman
chromatography paper No. 3 and soaked
for 3-5 minutes in Richard's solution
containing 100 ug/ml rose bengal, 100
ug/ml streptomycin sulfate, 5 ug/ml
active benomyl, and 5 ug/ml Cu from
Cupric sulfate. Treated disks were dried
at 41 C and stored in a sterile perti dish
until ready for use.
Shim brash (2 x 6 cm) was drilled
with two rows of holes (0.4 cm hole
diameter), three holes per row. The assay
disks were placed over the rows of holes
on one side of the plate and covered
with masking tape leaving one side
exposed on the other side. The assembled
disks were then placed in paper bags and
sterilized at 15 psi for 20 minutes.
Sterilized disk plates were then
inserted vertically in number 2 pots
containing the soil, incubated for 5-7
days, recovered, and freed of excess
soil. The tape was removed from the
plates and the disks were plated in
Rhizoctonia selective medium (2% water
agar containing bacterial inhibitors: rose
bengal, 100 ug/ml, streptomycin sulfate,
100 ug/ml). After 3 days at ordinary
room temperature (25-30 C) the plates
were examined for R. solani growth.
Hyphal tips were then cut and transferred
to PDA for father examination.

Sclerotium rolfsii
Sieving-flotation method was used
(Rodriquez-Kabana et al., 1974). Fifty
grams of soil was suspended in 0.5 liter
of tap water, stirred, poured on 50 mesh
screen and placed under a running water
from the faucet unitl the water coming
out on the other side of the sieve was
clear. Particles remaining in the sieve
were collected, floated in 200 ml
beaker of water, sclerotial bodies were
picked up, surface sterilized with 1:1000


HgC12 and plated on PDA.

Phytophtora parasitica var. nicotianae
Selective medium was that of
Flowers and Hendrix (1969). It consisted
of one liter distilled water, 30 g sucrose,
2 g NaNO3, 0.5 g MgSO4. 7H20, 1 g
Kh2PO4, 0.5 g yeast extract, 2 mg
thiamine HC1, 425 mg gallic acid, 0.5 mg
rose bengal, 25 mg PCNB, 80,000 units
penicillin G, 100,000 units nystatin, and
20 g agar.
Plates containing the medium were
inoculated with 1 ml of 1:50 soil suspen-
sion and incubated for 36 hours at 25 C
in dark. The soil was washed off with
running tap water and examined several
hours later.

Pathogenicity Test

To obtain information on the rela-
tive virulence of the different pathogens
isolates a pathogenicity test was con-
ducted.
The inocula were grown in PDA for
10 days prior to inoculation. Five petri
plates of each pathogen were mixed
separately with 2 liters of heat-sterilized
soil and the soil-fungus mixture was
incubated for another 10 days to permit
build up of inoculum. Control lots were
provided.
After 10 days, the soil medium was
placed in 15 x 5 cm wooden flats and
sown with 100 seeds of tobacco var.
Golden Harvest. The experiment was
conducted in the greenhouse using com-
pletely randomized design with four
replications.
Disease rating was taken 45 days
after sowing. The number of surviving
seedlings was used as criterion in measru-
ring infectivity.


Vol. 18









Damping-off disease of tobacco


Screening for Resistance

Twenty tobacco varieties were
used. The screening was done in the
greenhouse using a completely random-
ized design with four replications.
Wooden flats were used as seedbed.
The dimension of the flat was 100 x 40 x
5 cm and was further subdivided into
10 x 10 cm to make a total of 80 com-
partments, each compartment accommo-
dating one variety.
Soil inoculation was done as des-
cribed earlier. In screening for resistance
to mixture of pathogens 5 petri plates of
10-day old cultures of each organism
were mixed with 8 liters of sterile soil.
Ten days after inoculation wooden flats
were filled separately with soil infested
with a particular organism up to 2 cm
below the rim and sown with tobacco
seeds. Seeding rate was adjusted accor-
ding to percentage germination of each
variety to obtain uniform stand.
Damping-off evaluations was done
45 days after sowing and was based on
the number of surviving seedlings. Using
the rating scheme ofPuruganan (1978) the
reactions of the different varieties were
classified as follows:

HR = 100-95% seedling survival
(highly resistant)
R = 94-85% seedling survival (re-
sistant)
MR = 84-75% seedling survival
(moderately resistant)
MS = 74-65% seedling survival (mo-
derately susceptible)
S = 64-55% seedling survival
(susceptible)
HS = 54-below seedling survival
(highly susceptible)


RESULTS AND DISCUSSION

Field Incidence and Distribution
of Damping-off Pathogens

All seedbeds surveyed were in-
fested with damping-off. White patches
and toppled seedlings over the beds were
common (Fig. 1). Pythium sp. and
F. oxysporum f. nicotianae were the most
common. In contrast R. solani and
S. rolfsii were rarely detected and absent
in the samples collected from the provin-
ces of Abra and Cagayan, respectively
(Table 1).
Their difference in distribution may
be due to the difference in their survival
behavior in the soil. Soil is a natural habi-
tat of enormous number of micro-
organisms competing with one another
for survival. Garrett (1956) pointed out
that the effect of microbial population
on the pathogen depends largely on the
pathogen's level of competitive sapro-
phytic ability. He listed four general
attributes that are likely to contribute
to a high degree of competitive sapro-
phytic ability. One of them is the rapid
germination of spores and high rate of
hyphal growth, both favoring rapid
colonization. Pythium spp. have this
attribute (Lucas, 1975).
Like Pythium sp., F. oxysporum
f. nicotianae was also widely distributed.
Booth (1971) reported that Fusarium
spp. are abudantly endowed with the
means of survival, one of the mecha-
nisms of which is its capacity for rapid
change, often morphologically as well
as physiologically, to a new environemt.
R. solani has poor saprohytic competi-
tive ability and therefore its growth
in the soil will be adversely affected
(Parmeter, 1975) and perhaps so with
S. rolfsii (Papavizas, 1971). A common


Jan. & June 1982









Philippine Phytopathology


Fig. 1. Portion of tobacco seedbed in Batac, Ilocos Norte naturally infested with
damping-off Note the dead and rotted seedlings.

Table 1 Distribution of the different pathogens in the different areas surveyed.

ORGANISMa
PROVINCE
Pythium sp. F. oxysporum S. rolfsii R. solani

Ilocos Norte + + + +

Ilocos Sur + + + +
La Union + + + +
Pangasinan + + + +
Abra + + +
Isabela + + + +
Cagayan + + +


a+ = present

- = absent


observation, however, was that these
four pathogens were always associa-
ted with one another making damping-
off a complex disease. The influence
of their association is important to the
ecology of the disease.

Pathogenicity Test

Pythium sp. was the most patho-
genic where 21.75% of the seedlings


survived after 45 days (Table 2). The
post-emergence phase not only affected
the roots but also the leaves near the
soil surface. It is not uncommon there-
fore, for a field heavily infested with it
to have tobacco seedlings entirely wiped
out. Stanghellini and Hancock (1971)
reported that the special biological
characters of Pythium spp., their rapid
germination and growth rate contri-
buted to their effectiveness as damping-


Vol. 18









Damping-off disease of tobacco


Table 2. The pathogenic capabilities of the four pathogens on tobacco variety Golden Har-
vest based on the number of surviving seedlings 45 days after sowing.a

PERCENT SEEDLINGb
PATHOGEN SURVIVAL

Pythium sp. 21.75a
F. oxysporum f. nicotianae 34.25
R. solani 40.00bc
S. rolfsii 45.00c
Control 98.25e


aAverage of four replications.
bMeans followed by the same letter are not significantly different at 5% level by DMRT.


off pathogens.
F. oxysporum f. nicotine ranked
second with 34% seedling survived, fol-
lowed by R. solani, 40%, and S. rolfsii
45%. R. solani and S. rolfsii were also
pathogenic but because of their limited
distribution in the field their damage to
the crop may not be as severe as those
caused by Pythium spp. and F. oxy-
sporum f. nicotianae.

Varietal Resistance
The varieties exhibited varying
degrees of resistance to the four patho-
gens (Table 3). For S. roflsii two varieties
were resistant, these were Coker 139, and
Dixie Bright 102, and six were moderate-
ly resistant, namely: Buyers Choice,
Coker 411, 136, Oxford 26, Yarda, and
100 Leaves. For F. oxysporum f. nico-
tianae, three varieties were resistant,
namely; Coker 411, 139, and Dixie Bright
102, and two were moderately resistant,
Coker 136 and Reams 66. Only Virginia
21 was resistant to R. solani while three
were moderately resistant (Coker 411,
NCBY and Harison Special). In contrast
none of the varieties were resistant to
Pythium sp. and only four (NCBY, Coker


139, and Dixie Bright 102) were mode-
rately resistant.
The varieties Coker 139 and Yarda
were previously reported as resistant to
P. debaryanum (Pakdi and Calridad,
1971; Puruganan, 1978). Coker 139,
Dixie Bright 102 and Reams 66 were
reported also as resistant to Fusarium
(Lucas, 1975).
In general, resistance to damping-
off pathogens was observed only in the
Virginia types. In the comprehensive list-
ing by Lucas (1975) none of the varieties
of the filler and wrapper types used in
this study are resistant to any one of the
four pathogens used. Most of the resistant
varieties belong to the flue-cured tobacco.
None of the varieties resistant to
one or two of the four pathogens were
resistant to mixture of pathogens. The as-
sociation of these pathogens suggests
synergistic effect resulting to a more
severe disease development than when
either pathogen was used singly.
The identification of resistance
sources to the four pathogens is, however,
important for future breeding program.
Resistant variety remains the best answer
for practical long-range control of the
disease.


Jan. & June 1982








Table 3. Reaction of 20 tobacco varieties to individual and mixture of the four pathogens based on the number of surviving
seedlings 45 days after sowing.a

TYPE AND VARIETY S. roflsii F. oxysporum Pythium sp. R. solani Mixture
f. nicotianae
Virginia
Buyers Choice 76.50 (MR) 43.00 (HS) 55.00 (S) 56.50 (S) 46.25 (MS)
Coker 411 75.75 (MR) 88.50 (S) 49.50 (MR) 83.75 (HS) 53.75 (MS)
NCBY 67.00 (MS) 52.75 (HS) 77.50 (MR) 84.75 (MR) 50.50 (S)
Yellow Special 400 53.75 (HS) 68.75 (MS) 61.50 (S) 47.25 (HS) 45.75 (HS)
Coker 139 88.50 (R) 87.25 (R) 76.25 (MS) 67.50 (MR) 72.50 (MS)
Dixie Bright 102 86.25 (R) 86.25 (R) 79.25 (MR) 63.50(S) 59.50(S)
Coker 136 79.25 (MR) 75.75 (MR) 68.26 (MS) 56.75 (MS) 72.75 (MS)
Oxford 26 77.25 (MR) 43.00 (HS) 38.50 (HS) 59.75 (S) 39.75 (HS)
Reams 66 53.50 (HS) 79.25 (MR) 51.25 (HS) 54.50 (HS) 48.75 (HS)
Golden Mammoth 45.50 (HS) 46.50 (HS) 49.50 (HS) 54.50 (HS) 49.75 (HS)
Golden Cure 59.50 (S) 67.25 (MS) 55.00 (S) 41.25 (HS) 47.00 (HS)
Yarda 81.75 (MR) 48.00 (HS) 52.50 (HS) 59.53 (S) 63.75 (S)
Vamorr 5 47.25 (HS) 58.25 (S) 37.75 (HS) 44.50 (HS) 51.75 (HS)
Harrison Special 54.00 (HS) 40.25 (HS) 44.00 (HS) 76.75 (MR) 48.50 (HS)
Virginia 21 53.25 (HS) 53.50 (HS) 57.75 (S) 86.50 (R) 57.00 (S)








TYPE AND VARIETY S. roflsii F. oxysporum Pythium sp. R. solani Mixture
f nicotianae


Cigar-filler
Akib 52.25 (HS) 44.50 (HS) 39.50 (HS) 47.50 (HS) 42.75 (HS)
Romero 52.25 (HS) 43.00 (HS) 41.75 (HS) 48.25 (HS) 46.00 (HS)
Havana 503 48.00 (HS) 42.75 (HS) 40.00 (HS) 54.50 (HS) 29.00 (HS)
Cigar Wrapper
Reax 50.50 (HS) 49.75 (HS) 45.25 (HS) 65.75 (MS) 36.25 (HS)


aSymbols used
R = resistant (94-85% seedling survival)
MR = moderately resistant (84-75% seedling survival)
MS = moderately susceptible (74-65% seedling survival)


S = susceptible (64-55% seedling survival)
HS = highly susceptible (54%-below seedling survival)









Philippine Phytopathology


LITERATURE CITED

BOOTH, C. 1971. The genus Fusarium. Kew. CMI, England. 237 p.

CLARA, F.M. 1925. Diseases of Tobacco nicotianaa tabacum) in the Philippines. Philipp.
Agr. Rev. 18:564-570.

DALMACIO, S.C. 1979. Breeding for disease resistance. FFTC Ext. Bull. No. 129, 9 p.

DAVID, P. A. and E. F. ROLDAN N. 1926. Important field diseases of tobacco in the
Experiment Station at Los Banos and in Northern Luzon, Phil. Islands. Philipp.
Agr. 15: 287-301.

FLOWERS, R.A. and J.W. HENDRIX. 1969. Gallic Acid in a procedure for isolation of
Phytophtohora parasitica var. nicotianae and Pythium sp. form soil. Phytopatho-
logy. 59:725-731.

GARETT, S.D. 1956. Biology of Root-Infecting Fungi. Cambridge University Press,
England, 293 n

HERR, L.J. 1973. Disk-plate method for selective isolation of Rhizoctonia solani from
soil. Can J. Microbiol. 19:1269-1273.

LUCAS, G.B. 1975. Diseases of Tobacco. (3rd ed.) Biological Consulting Associates.
Raleigh, North Carolina, 593 p.

NASH, S.M. and W.C. Snyder. 1972. Quantitative estimation by plate count and pro-
pagules of soybean root rot Fusarium in field soil. Phytopathology. 52-567-572.

PAKDI, S. and F.B. CLARIDAD. 1971. Screening of some tobacco varieites for resis-
tance to damping-off disease caused by Pythium debaryanum Hesse. Araneta J.
Agric. 18:166-186.

PAPAVIZAS, C.G. 1971. Isolation and enumeration of propagules of Sclerotium cepi-
vorum from soil. Phytoppathology. 62:545-549.

PARMETER, J.R. 1970. Rhizoctonia solani Biology and Pathology. Berkeley University
Cal. Press, 255 p.

PURUGANAN, F.G. 1978. Distribution, taxonomy and pathogenicity of Pythium as-
sociated with tobacco in the Ilocos Region. MS Thesis, UPLB, College, Laguna.
79 p.

RODRIGUEZ-KABANA, R.P., A. BACKMAN, and E.A. WIFFINS. 1974. Determina-
tion of sclerotial populations of Sclerotium rolfsii in soil by a rapid flotation-
sieving technique. Phytopathology. 64-610-615.

STANGHELLINI, M.E. and J.G. HANRECK. 1971. The sporangium of Pythium ultimum
as a survival structure in soil. Phytopathology. 61:157-164.


VoL 18









Philipp. Phytopathol. 18: 43-47


WILT DISEASE OF COCONUT IN SOCORRO, ORIENTAL
MINDORO: I. SURVEY (1977-1981)

E. C. CONCIBIDO, R. G. ABAD and J. G. NUEVAS, JR.


Research Staff, Crop Protection Division, Davao Research Center, Agricultural
Research and Development Branch, Philippine Coconut Authority, Bago-Oshiro, Davao
City and Provincial Coconut Development Officer, Region II, Philippine Coconut
Authority, Calapan, Oriental Mindoro.

ABSTRACT

A lethal wilt disease of coconut in the Philippines occurs in the municipality of
Socorro, Oriental Mindoro. According to some Socorro residents, it was first observed
in the early 60's and has killed an unestimated number of palms in the area. From
1977 to 1981, the disease has been observed in 6 barangays of the municipality where
nearly 7,000 palms (mostly 25 years old and below) were reckoned to have succumbed
to the disease. The disease still occurs despite the 'cut and bur' operations conducted
in 1977, 1978 and 1980.
The disease spread in a 'leap frog' pattern suggesting infectious nature of the
malady, probably disseminated by airborne vector(s). The 4 surveys conducted within
5 years also showed a yearly average rate of disease incidence of 1.4, 1.03, 4.06 and
0.85%; the high figure for the third survey being attributed to the high combined
incidence of 2 years (1979-1980).
There are unconfirmed reports that the disease is present in other municipalities
of the province, therefore, deserving further attention.
It can be concluded that the disease is alarming, hence research on etiology
and especially control measures are of paramount importance.


The occurrence of lethal wilt disease
of coconut was first noted in the early
60's in Socorro,northern town of Oriental
Mindoro. So far, it is the first recorded
wilt disease of coconut to occur over a
wide area in the Philippines. It was
brought to the attention of the Philip-
pine Coconut Authority in 1976 (Ilagan,
1976). Initially, it was reported to occur
in three barangays of Socorro, namely:
Mabuhay, Happy Valley and Subaan. A
year after, the disease was observed in
three other barangays, namely: Batong-
Dalig, Monteverde and Calubayan (Figure
1). From 1977 to 1981, nearly 7,000
palms were reported to have succumbed
to the disease (Abad, 1981).
The disease affects palms 25 years old
and below. Its earliest symptom is prema-
ture senescence of the fronds starting
from the oldest to the youngest foliage.


The youngest leaves stay upright for a
few weeks before collapsing. Premature
nutfall and eventual cessation of repro-
ductive growth and root rot accom-
pany these symptoms (Abad et al., 1980).
It takes about 3 to 7 months for di-
seased palms to die from the appearance
of early symptoms (Abad et al, 1981).
The disease occurs in a 'leap frog' pattern
suggesting an infectious nature of the
malady probably spread by airborne
vector(s).
There are apprehensions in the coco-
nut industry sector that the disease,
whose etiology is still unknown, may
become another 'cadang-cadang' expe-
rience if left unchecked. Along this pre-
mise, survey and observations on disease
occurrence should provide additional in-
formation on the disease and the formu-
lation of remedial measures against it.









Philippine Phytopathology


Fig. 1. Map of the Philippines showing the coconut wilt-affected province
of Oriental Mindoro (right inset). Lower inset shows the munici-
pality of Socorro and its barangays including place and year the
disease was observed (Maps not drawn to scale; Lifted from Abad
et al., 1980).


VoL 18









Wilt disease of coconut


MATERIALS AND METHODS

After the report of Ilagan (1976),
technical men of the Philippine Coco-
nut Authority's (PCA's) Oriental Min-
doro staff surveyed, in 1977, the areas
where the disease was reported to occur.
Three barangays of Socorro were visited,
namely: Mabuhay, Happy Valley and
Subaan. At the same time, a 'cut and
burn' operation of affected palms in these
areas was launched by PCA and Philip-
pine Coconut Producers Federation
(COCOFED) to hopefully check disease
incidence by reducing if not eradicating
sources of inoculum.
In 1978, a resurvey was conducted in
the municipality to assess the effects of
the 'cut and burn' operation. Hundreds
of diseased palms were still recorded in
the areas. In addition, the survey revealed
the presence of the disease in three other
barangays, namely: Monteverde, Calu-
bayan and Batong-Dalig. A 'cut and
burn' operation was again conducted
right after the survey. From then on,
surveys in the diseased areas were con-
ducted yearly up to 1981 except in 1979
but a 'cut and burn' operation was again
instituted in 1980.
From the surveys, observations and
operations, the whole situation was
assessed. Disease incidence per area per
year was determined based on the total
diseased palms over the total coconut
population in each barangay. An attempt
of determining the rate of disease spread
was also made by plotting disease inci-
dence against time (year).

RESULTS AND DISCUSSION

Survey data as presented in Table 1
showed barangay Mabuhay to have the
highest disease incidence at 1,107 infec-
ted palms in 1977. It was also learned
from Mabuhay residents that the disease
was first noted in the early 60's in this
barangay. The high incidence could be


attributed to the long presence of the
disease in this locality.
A decrease in the total number of in-
fected palms is also shown in Table 1.
From a total of 1,524 infected palms
in 1977, only 1,109 infected palms were
recorded the following year. This suggests
that the 'cut and burn' operation to some
extent played a role in reducing disease
incidence. To support this suspicion, no
'cut and burn' operation was conducted
in 1979 and an increase in the number
of infected palms (2,981) was recorded
in 1980. Thereafter, a decreased inci-
dence (1,177 infected palms) was again
noted in 1981 after the 'cut and burn'
operation of the proceeding year. With
these trends, it can be assumed that
disease incidence is affected by the pre-
sence of inoculum sources. The fairly
high number of diseased palms still
observed from year to year despite the
'cut and bum' operation of 1977, 1978,
and 1980 may be attributed, among other
things, to the presence of inoculum
sources in the form of a) infected palms
that were missed during the 'cut and
burn' operations, b) diseased palms
which manifested wilt symptoms only
after the operations, and c) alternate
hosts, if any. This indicate that the 'cut
and burn' operations, solely at least, may
work out as a remedy against disease in-
cidence.
As seen in Table 2, no significant
trends in rate of disease increase can be
discerned from the surveys and observa-
tions due to the marked fluctuations in
the yearly occurrence in the various
barangays as a result apparently of the
'cut and burn' operations. From these
data, therefore, incidence rate and its
relation to some factors cannot be
drawn up except to support previous
statements on the slightly favorable
effects of 'cut and burn' operations.
As previously reported, the unpre-
dictable mode of disease spread suggests
its infectious nature probably dissemi-


Jan. & June 1982










Table 1. Yearly wilt disease incidence in the six (6) barangays of Socorro, Oriental Mindoro (1977-1981).


WILT DISEASE INCIDENCE/YEAR


1977 (June) 1978 (March) 1979-1980 (April) 1981 (April)a


Total No. of
pop. infected
palms


Total No. of Total No. of Total No. of Total No.
pop. infected pop. infected pop. infected of Infected
palms palms palms Palms


Mabuhay 29974 1107 28867 327 28540 689 27851 191 2314

Happy Valley 38271 138 38133 88 38045 85 37960 640 951
Subaan 60841 279 60562 282 60280 593 59685 155 2231
BatongDalig 5610 NR 5610 36 5574 79 5495 16 131
Calubayan 18892 NR 18892 88 18804 217 18587 59 364
Monteverde 7196 NR 7196 368 6828 1316 5521 116 1800


TOTAL INFECTED PALMS 1524 1109 2981 1177 6791


period covered under report
NR no report


BARANGAYS









Wilt disease of coconut


Table 2. Yearly percentage disease incidence of Socorro Wilt.

PERCENTAGE INCIDENCE/YEAR
LOCALITY
1977 1978 1979-1980 1981

Mabuhay 3.6 1.13 2.4 0.6

Happy Valley 0.3 0.2 0.2 1.6
Subaan 0.4 0.4 0.9 0.2
Batong-Dalig NR 0.6 1.4 0.3

Calubayan NR 0.5 1.2 0.3
Monteverde NR 5.1 18.3 2.1

MEAN 1.4 1.03 4.06 0.85

NR no report.


nated by airborne vector(s). This is sus-
pected since the distance of one or seve-
ral infected palms to another are rela-
tively far to be attributed to a soil-borne
vector(s). In addition, this mode of
disease distribution virtually eliminates
abiotic factors (i.e. soil deficiency or toxi-
city) as primary causes of the malady.
Dissemination by mechanical means may
be overruled since previous mechanical
or sap transmission trials yielded nega-
tive results (Abad, 1981).
To determine rate of disease incidence
or infection, blocks of diseased areas


should be further observed from year to
year and where no 'cut and bum' opera-
tions shall be done. It is also necessary
that survey of other municipalities in
Oriental Mindoro be conducted to con-
firm reports that the disease occurs in
areas other than Socorro.
The nature of the disease suggests
its major importance hence quarantine
measures have been instituted in the pro-
vince. Etiological studies are being
pursued which are needed in formulating
remedial measures. Screening for disease
resistance has also been started.


LITERATURE CITED

ABAD, R.G. 1981. Wilt disease of coconut in Socorro, Oriental Mindoro. M.S. Thesis.
UPLB-CA College, Laguna.

D.A. BENIGNO and J.G. NUEVA, JR. 1980. A hitherto unreported wilt
disease of coconut in the Philippines. Philipp. J. Coco, Studies 5: 1-19.
ILAGAN, J.A. 1976. Report re: an unknown disease of coconut in Socorro, Oriental
Mindoro. Official communication to the PCA Regional Administrator Region II,
November 2, 1976.


Jan. & June 1982









Philipp. PhytopathoL 18: 48-55


SIMULTANEOUS AND SEQUENTIAL TRANSMISSION OF
ABACA-MOSAIC AND BANANA-MOSAIC VIRUSES
TO ABACA (MUSA TEXTILIS NEE) BY APHIS
GOSSYPII GLOVER

M. L. RETUERMA

Research Plant Virologist, RP-German Seed Potato Program, BPI, Baguio City
Portion of the author's dissertation presented in partial fulfillment for the degree
degree of Doctor of Philosophy (Plant Pathology), Graduate School, University of the
Philippines at Los Banos (UPLB), College, Laguna.


ABSTRACT
Abaca-mosaic and banana-mosaic viruses were simultaneously or sequentially
transmitted to abaca (Musa textilis Nee) by a common vector, Aphis gossypii Glover.
Both viruses transmitted to abaca showed no interference or antagonistic effect to each
other but produced more severe symptoms and stunted growth than single infection of
either virus. Each virus acted independently by producing its own characteirstic symp-
toms in the same host.
Flexuous rod-like and isometric virus particles measuring 650-750 nm in length
and 28-30 nm in diameter, respectively, were both observed under the electron micros-
cope in crude sap extracted from abaca used in simultaneous and sequential transmis-
sion tests. Positive serological reaction was observed only against cucumber mosaic
virus Y (CMV-Y) antiserum.


It is common in nature that plants
may be infected with two or more viruses.
This may result to either more severe
symptoms than single infection (syner-
gism,) or interference with the multipli-
cation and/or manifestation of symptoms
(antagonism). However, in most cases,
each of the viruses seems to act inde-
pendently producing its own symptoms
(Agrios, 1969).
In the previous reports, abaca mosaic
virus was readily transmitted to abaca by
several aphid species (Ocfemia, 1949;
Celino and Ocfemia, 1941; Celino, 1940;
Gavarra and Eloja, 1966), and one of
them was Aphis gossypii Glover (Ocfemia
and Celino, 1938). Likewise, the banana
mosaic virus was found to be transmitted
by A. gossypii Glover to banana (Stover,
1926) and abaca (Magnaye and Eloja,
1968). Abaca mosaic virus was not trans-
mitted to banana (Celino and Martinez,


1956), but banana mosaic virus was
transmitted to both abaca and banana
(Magnaye and Eloja, 1968) mechanical-
ly. Abaca mosaic and banana mosaic
viruses were separately transmitted by
A. gossypii to abaca (Retuerma, un-
published).
Since abaca mosaic and banana mosaic
viruses were found to be transmitted to
abaca by a common vector A. gossypii,
it is interesting to know if both viruses
can be transmitted simultaneously and
sequentially to abaca and observe the
mode of transmission by means of A.
gossypii Glover and to know the relation-
ship ob both viruses in the same host. The
study was conducted at the screenhouse
and the virus laboratory of the Depart-
ment of Plant Pathology, University of
the Philippines at Los Banos from
November 1980 to October 1981.









Transmission of abaca- and banana mosaic


MATERIALS AND METHODS

Propagation of virus-free aphid colony
Adult aphids, A. gossypii Glover were
collected from cotton plants in the field
and allowed to multiply on cotton seed-
lings enclosed in a big insect cage. From
time to time some aphids were allowed
to feed on Echinocloa colona (L.).
Link cotton seedlings, a very susceptible
host to abaca mosaic virus, were used to
determine if the aphids being propagated
and multiplied were virus-free. The virus
free aphids were used in the transmission
studies.

Transmission of abaca and banana mosaic
viruses
Virus-free adult aphids (A. gossypii
Glover) were collected and starved for 1
h and allowed to feed on leaves infected
with abaca or banana mosaic for another
hour after which they were fed on the
test plants. At least 30 aphids were
transferred to each test plant. Test plants
containing viruliferous aphids were then
caged in a rectangular plastic cage of 6 cm
x 10 cm x 5 cm for a period of 24-h ino-
culation feeding time.

Simultaneous transmission of abaca and
banana mosaic to abaca by Aphis gossypii
Glover
Two groups of virus-free aphids were
starved for 1 h. One group was allowed
acquisition feeding on abaca leaves in-
fected with abaca mosaic and the other
on abaca infected with banana mosaic.
These two groups of aphids were simul-
taneously transferred to a healthy abaca
seedling and allowed inoculation feeding
time of 24 h. Test plants were observed
daily for symptoms.

Sequential transmission of abaca mosaic
virus and banana mosaic virus to abaca
by A. gossypii Glover
Virus-free aphids (A. gossypii) were
starved for 1 h and allowed to feed for


1 h on abaca leaf infected with abaca
mosai: and transferred to a healthy abaca
seedlirg for 24 h. Seven to 14 days
after the healthy abaca became infected
with abaca mosaic, it was reinoculated
with aphids that were allowed to feed for
1 h in abaca leaf infec ed with banana
mosaic virus.
In another set, aphids were allowed to
feed for 1 h on banana leaf infected with
banana mosaic virus and allowed to feed
for 24 h on a healthy abaca seedling.
Seven to 14 days after this abaca plant
became infected with banana mosaic
virus, it was reinoculated with aphids
that were allowed to teed for 1 h on
abaca infected with abaca mosaic virus.
Test plants were observed daily for
symptoms of infection.

Electron Microscopy
A modified leaf dip method was used
with crude sap extracted from tissue of
abaca simultaneously or sequentially
infected with abaca mosaic and banana
mosaic viruses.
A small piece of infected tissue was
macerated in a glass slide with a metal
spatula, until a small amount of sap was
extracted and mixed with a drop of 2%
phosphotungstic acid (PTA). A small
amount of this mixture was carefully
dropped on a prepared EM grid, and
allowed to stand for 5 minutes. Excess
liquid was removed by touching the edge
of the drop with a piece of filter paper.
The grid was air-dried and examined
immediately under the electron micros-
cope.
A JEOL 100 U transmission electron
microscope of the National Science Re-
search Center, U.P. Diliman, Quezon City
was used.
Serology
Ouchterlony (1962) agar-gel double
diffusion technique was followed. An 0.8
g ionagar was dissolved in 90 ml citrate
buffer (0.05 M, pH 7.0) in a water bath.
About 0.85 g sodium chloride, 0.25 g


Jan. & June 1982









Philippine Phytopathology


sodium azide and 0.1 g sodium dodecyl
sulfate (SDS) were dissolved in 1 ml
citrate buffer by heating, added to the
melted agar. About 10-15 ml of agar
solution was poured in a sterile petri dish
and allowed to solidify.
A 3-center well surrounded by 10
peripheral well pattern was cut using a 5
mm diameter cork borer. Plugs were
aspirated, and melted agar was dropped
on each well to seal seepage between the
agar and the glass.
The center wells (left to right) were
filled with sugarcane mosaic virus A
(SCMV-A), cucumber mosaic virus Y
(CMV-Y) and potato virus Y (PVY)
antisera. Row of peripheral wells was
filled with crude sap from abaca infected
with abaca mosaic and reinoculated with
banana mosaic virus. The second row of
peripheral wells was filled with crude sap
extracted from abaca infected with
mosaic virus.
Wells at the extremities of the center
wells were filled with saline as controls.
Antigens were diluted to 1:1 with 3%
SDS and allowed to stand for 1 h before
being used in serological tests.
Reading of the plants was made after
overnight incubation over a box with a
hole with indirect light.


RESULTS


Transmission of abaca and banana mosaic
viruses to abaca by A. gossypii Glover
Abaca inoculated separately with
abaca and banana mosaic viruses pro-
duced typical symptoms of each disease
after 7-14 and 12-14 days, respectively.
Abaca infected with abaca mosaic
virus exhibited yellow-spindle-shaped
lesions which later elongate into narrow
yellow dashes and yellow stripe origina-
ting from the midrib to the leaf margin.
Dark green dashes along the veins occur.
The symptoms of banana mosaic on
abaca were the presence of yellow-orange


streaks with broken edges of irregular
alignment.

Simultaneous transmission of abaca-
mosaic and banana-mosaic viruses to
abaca by A. gossvpii Glover.
Abaca inoculated simultaneously with
abaca and banana mosaic viruses pro-
duced symptoms typical of abaca mosaic
virus infection in 14-16 days on the new-
ly opened leaf and the leaf became
narrowed with the tip in a whip-like
appearance. Leaf margin was wavy and
curled. Later symptoms of both diseases
appeared in the succeeding leaves (Fig.
1).


Vol. 18












Jan. & June 1982


Transmission of abaca- and banana-mosaic


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Philippine Phytopathology


Sequential transmission of abaca and
banana mosaic viruses to abaca by A.
gossypii Glover
In the sequential transmission, abaca
infected with banana mosaic and re-
inoculated with abaca mosaic exhibited
more severe mosaic symptoms of yellow
streaks with broken edges typical of
banana mosaic infection and yellow
stripes with dark green dashes along the
veins, a symptom of abaca mosaic infec-
tion in 12-14 days. The leaf became
narrowed on one side of the blade from
the midrib. Abaca infected with mosaic
and reinoculated with banana mosaic


produced yellow streaks with broken
edges in 14-16 days. The dark green
dashes along the veins were greatly reduced
in the succeeding leaf (Fig. 2a and 2b).
Flexuous rod-like and isometric virus
particles measuring 650-750 nm in length
and 28-30 nm in diameter, respectively,
were both observed in electron micro-
scopy of tissues of test plants used in
sequential transmission (Fig. 3).
Reactions were observed only against
CMV-Y antiserum, (Fig. 4) in serological
test of sap from abaca used in sequential
transmission of abaca-mosaic virus and
banana mosaic virus.


Fig. 3. Flexuous rod-like (fr) and isometric (iso) virus particles (both observed)
under the electron microscope in crude sap from abaca used in simultaneous
and sequential transmission tests.
Fig. 4. Serological reaction using crude sap from abaca used in simultaneous and
sequential transmission tests.
Row 1 abaca mosaic virus to abaca infected with banana mosaic virus (A/B)
Row 2 banana mosaic virus to abaca infected with abaca mosaic (B/A)
Center wells SCMV-A: CMV-Y; PVY-antisera


Vol 18









Transmission of abaca- and banana mosaic


DISCUSSION

Results of this study showed that
abaca mosaic and banana mosaic viruses
were readily transmitted simultaneously
or sequentially by a common aphid vec-
tor. A. gossypii Glover. No inhibitory
or antagonistic effects were observed
in the same host such that narrowing
of the leaf blade on one side from the
midrib, severe mosaic causing corrogation
on the leaf margins and stunted growth
were observed. Each virus produced its
own distinct symptoms in the inoculated
abaca.
In simultaneous transmission, typical
symptoms of each virus alternated in
the leaf blade of the infected abaca.
Abaca mosaic virus induced short and
long yellow stripes extending from the
midrib to the leaf margin with dark green
dashes along the veins. These symptoms
were also described by Celino (1940).
Banana mosaic virus induced yellow-
orange streaks with broken edges (Re-
tuerma, 1981). Severe mottling caused by
both viruses caused corrugation of the
leaf margin of infected leaf.
In the sequential transmission, typical
symptoms of abaca mosaic virus infec-
tion gradually reduced after reinfection
with banana mosaic virus, until symptoms
of each virus appeared equal in the in-
fected leaf blade. The same sequence was
observed in abaca infected with banana
mosaic and later reinoculated with abaca
mosaic virus. The narrowing of the infec-
ted leaf on one side from the midrib to
the leaf margin was observed, and could
be due to banana mosaic virus infection.
This symptom was not observed in abaca
infected alone with abaca mosaic virus
(Retuerma, 1981).
The presence of both flexuous rod-like
and isometric virus particles in crude sap
from tissues used in simultaneous and
sequential transmission is an evidence
that both viruses were transmitted to
abaca by A. gossypii.


Positive serological reactions against
cucumber mosaic virus Y (CMV-Y) anti-
serum is an added evidence that abaca
infected with abaca mosaic was later
reinfected with banana mosaic virus.
Banana mosaic virus was found serolo-
gically related to CMV-Y antiserum
(Wardlaw, 1953; Retuerma, 1981). The
negative serological reactions of abaca
mosaic virus with SCMV-A and PVY,
which are all scrologically related may
be due to the unstability of the virus
in vitro and the normally low concentra-
tion of the virus in the crude sap.
The pronouncement of Kent (1954)
that abaca mosaic is caused by a complex
of viruses had some validity in this res-
pect. Banana mosaic virus, a distinct virus
from abaca mosaic virus is capable of
being transmitted simultaneously and se-
quentially to abaca by a common vector,
Aphis gossypii Glover.
The results of the study have some
implications to multiple cropping systems.
It is not advisable to set-up abaca and
banana plantations side by side for abaca
is the common host of abaca and banana
mosaic viruses. The presence of these two
viruses in abaca have synergistic effects in
the disease syndrome and more damage
results in abaca than in banana.


Jan. & June 1982









Philippine Phytopathology


LITERATURE CITED

AGRIOS, G. N. 1969. Plant Pathology, Academic Press New York and London. 629 p.

BALL, M. E. 1974. Serological tests for the identification of plant viruses. The American
Phytopath. Soc. 31 p.

BRENNER, S. and R. CO HORNE. 1959. A negative staining for high resolution electron
microscopy of viruses. Biochem. Biophys. Acta 43: 103-110.

CALINISAN, M. R. 1938. Transmission experiment of abaca mosaic. Philipp. Agr. 9:3-9-
313;

CASTILLO, B. S. 1950. Transmission of banana mosaic in the Philippines. Plant Ind. Dig.
15: 39.

CELINO, M. S. 1940. Experiments on the transmission of mosaic of abaca or Manila Hern
plant (Musa textilis Nee). Philipp. Agr. 29(5): 379-405.

CELINO, M.S. and G. O MARTINEZ. 1956. Transmission of viruses from different plants
to abaca ((Musa textilis Nee). Philipp. Agr. 40: 285-302.

CELINO, M.S. and G. O. OCEFEMIA. 1941. Two additional insect vectors of abaca
mosaic of abaca or Manila hem plant and transmission of its virus to abaca. Philip.
Agr. 30: 70-78.

ELOJA, A. L., L. B. VELASCO and J. A. AGATI. 1962. Studies on the abaca mosaic. I
sap transmission of abaca mosaic virus. Philipp. Agr. 27: 75-84.

GAVARRA, M.R. and A. L. ELOJA. 1964. Experimental transmission of the abaca
mosaic by Toxoptera cetricidus (ker Kaldy). Philipp. J. Agr. 29: 47-54.

GAVARRA, M. R. and A. L. ELOJA. 1966. a. Further studies on the insect vectors of
abaca mosaic virus. I. The transmission of abaca mosaic by Aphis gossypii Mat.
Philipp. J. Plant Ind. 31: 9-14.

GIBBS, A. and B. HARRISON. 1976. Plant Virology. The principles. A Hoisted Press
Book, John Wiley and Sons, New York. 292 p.

KENT, G. C. 1954. Abaca mosaic. Philipp. Agr. 37: 555-591.

MAGNAYE, L. V. and A. L. ELOJA. 1968. Preliminary studies on the banana mosaic
in the Philippines. Philipp. Phytopath. 4;10-11 (Abstr.)

OCFEMIA, G. 0. 1937. The abaca disease situation in Davao. Philipp. Agr. 26: 229-236.


Vol. 18









Jan. & June 1982 Transmission of abaca- and banana-mosaic 55


OCFEMIA, G. O. and M. S. CELINO. 1938. Transmission of abaca mosaic. Philipp.
Agr. 27: 593-608.

OCFEMIA, G. O. and M. S. CELINO. 1939. Mosaic of abaca. NRCP Ball. 23: 179 p.

OUCHTERLONY, 0. 1962. Diffusion in gel. Methods for immunological analysis. Progr.
Allergy 6:30-154.

RETUERMA, M. L. 1981. Mosaics of abaca (Musa textilis Nee) and banana (Musa sapien-
tum (L.) Kuntz): Their causal viruses and properties. Ph.D. Dissertation, University
of the Philippines at Los Banos. 109 p.

ROPEROS, N. L. 1969. Notes on field incidence of banana mosaic in the Philippines.
Philipp. Phytopath. 5: 17 (Abstr.)

STOVER, K. M. 1926. A text book of plant virus diseases. Academic Press, Inc. 670 p.

WARDLAW, C. W. 1935. Diseases of banana and of the Manila hemp plant. MacMillan,
London. 615 p.








Philipp. PhytopathoL 18: 56-60


ECONOMIC HOSTS OF PSEUDOMONAS SOLANA CEA RUM
EFS ISOLATES FROM ABACA

A. R. RILLO

Portion of M.Sc. Thesis submitted to the UPLB Graduate School, College of Agri-
culture, College, Laguna, Philippines.
Research Supervisor, Philippine Coconut Authority, Albay Research Center,
Guinobatan, Albay, Philippines.

ABSTRACT
Eleven economic plants belonging to 5 families were artificially and naturally
inoculated with P. solanacearum isolates from abaca.
Results showed that potato, castor bean, eggplant, tobacco, tomato, diploid
banana, abaca, and heliconia were infected upon artificial inoculation with the organ-
ism. Under natural conditions, however, only castor bean, tomato, and eggplant were
infected.
The isolates failed to infect abaca under natural conditions suggesting the
possible role of biotic or abiotic agents in disease occurrence.
The results of the study showed that the organism exists as a variable species
with various pathogenic potentials in plants.


Bacterial wilt of abaca (Musa textilis
Nee) has been reported in Peru and the
Philippines. In Peru, it is known to be
caused by Pseudomonas solanacearum
strain infecting banana (Revilla and Var-
gas, 1968). In the Philippines, the initial
investigation on abaca wilt was made by
Calinisan (1938) when the disease was
first observed to cause considerable
damage in some abaca areas in Davao
provinces. Almost 4 decades later, Zehr
(1970) provided evidence that the disease
is caused by P. solanacearum. The strain
associated with the disease was found
apparently weakly virulent to abaca but
variably pathogenic to the commonly
used test plants.
This study was initiated to determine
the host range of the bacterium by artifi-
cial and natural inoculations.

MATERIALS AND METHODS

Bacterial colonies from wilted abaca
plants (Fig. 1) obtained from the Bureau
of Plant Industry, Davao City, southern
Philippines were isolated, purified by
several streaking in Kelman's medium,
and were used for artificial and natural


inoculations on the following test plants:
tomato (2029; Improved Harbot), tobac-
co (Vizbur; Bottom Special), sweet
pepper (Pimiento), eggplant (Dumaguete
Long Purple; Black Beauty), potato
(White skin?), ginger (Yellow Hawaiian),
peanut (CES 101), cowpea (VS 67-8),
castor bean (Hazera 22), bananas [Laka-
tan (AAA); Latundan (AAB); Butuhan
(BB); Giant Cavendish (AAA)], abaca
(Tangongon), and Heliconia latispatha
Benth.
Artificial inoculations on 4-5 week
old legumes, solanaceous plants, tobacco,
and castor bean seedlings were made by
placing on the axil of the first or second
leaf a drop of bacterial suspension from
24-h old streak culture standardized at
50% transmittance on a Bausch and
Lomb Spectronic 20 Spectrophotometer.
A pointed insect pin was pricked through
this drop into the stem to introduce the
bacterial cells into the plant vessels.
Abaca and banana plants were inoculated
by pouring 5 ml of the suspension into
the exposed and injured lateral roots
5-10 cm from either base or corm.
Ginger and heliconia plants were inocu-
lated by injecting 2 ml inoculum into









Hosts of Ps. solanacearum


the base of the stem with the aid of 5-ml
disposable syringe.
Two to 8 seedlings of each test plants
were used for inoculation. The natural
method of inoculation made use of
healthy seeds or seedlings planted on
the infested soil and decomposing plants
which resulted from artificial inocula-
tions described above. In both methods,
plants were observed for 7 weeks.

RESULTS AND DISCUSSION

Table 1 shows the summary results
of artificial inoculations of abaca isolates
to the different test plants. Ginger, pea-
nut, cowpea, and pepper were not infec-
ted by any of the isolates. Three isolates
(MT 1, MT 3, MT 10) were found to in-
fect potato, castor bean, eggplant, toma-
to, diploid banana, abaca, and heliconia
but failed to infect the bananas. Other
isolates (DES 2, DES 13, TA 3) were
found to infect only castor bean, white
potato, tomato, tobacco, and eggplant
but not the other test plants.
On abaca, the early noticeable symp-
toms were the cupping of the edges of
the leaf blades accompanied by loss of
glossiness which usually recover after 7
weeks. In some instances cupping was
followed by shrivelling of the midrib and
petiole resulting to general yellowing of
1 or 2 leaves. Leafsheath dried also but
without affecting the inner or adjacent
leafsheaths. The plants recovered from
the disease despite initial drying of 1 or 2
leaves.
The prominent symptoms on heliconia
were the yellowing and rotting of young-
est folded leaf or wilting of 1 leaf 2 weeks
after inoculation but rotting did not pro-
gress and plants recovered from wilting.
In Butuhan, rotting or wilting of young-
est expanded leaf occurred 2-3 weeks
after inoculation and progressed until all
the leaves turned yellow and dry.
Eggplants and castor bean plants exhi-
bited typical wilt syndrome within 1
week after inoculation and death within


6 weeks while tomato plants exhibited
rapid wilting and death in less than
2 weeks. Potato plants showed vascular
browning, wilting and death within 2.5
weeks after inoculation. Tobacco plants
showed limited necrosis at the point of
inoculation or partial wilting of 1 leaf 3
weeks after inoculation; the disease how-
ever, did not progress during the observa-
tion period.
Based on artificial inoculation studies,
abaca isolates appeared to be race 1
which conforms with the works of Zehr
(1970) and scheme of Buddenhagen,
Sequiera, and Kelman (1962).
The summary results of natural inocu-
lations are shown in Table 2. Three iso-
lates (DES 2, DES 13, TA3) did not in-
fect all the test plants while three other
isolates infected castor bean, tomato, and
eggplant. The failure of the isolates to
infect abaca under natural conditions and
the consistent recovery from initial
infections of artificially inoculated abaca
plants indicate the doubtful role of
P. solanancearum in the natural occur-
rence of bacterial wilt (Zehr, 1970;
Quimio, 1976). It is suspected that biotic
or abiotic agents are associated with the
organism in nature (Quimio, 1976). The
ability of the isolates to infect solanaceous
crops like tomato, eggplant, and castor
bean under natural conditions implies a
careful appraisal of the implementation
of farming activities that may result to
increased population of the virulent
strain, rapid spread, and possibly epiphy-
totics in a locality.
The results of the study imply further
that P. solanacearum exists as a variable
species with various pathogenic potential
(Buddenhagen, 1961). More information
is necessary to avoid confusion in deal-
ing with disease origin and spread, to
know the role of weed host species in
epiphytotic outbreaks, and to know the
possible effect of crop rotation and
fallowing as means of control measures.


Jan. & June 1982










Philippine Phytopathology


Fig. 1. Abaca plants naturally infected with bacterial wilt in Bago-Oshiro, Davao City.


Vol. 18


~ / + :: : aj & I









Hosts of Ps. solanacearum


Table 1. Summary of the reactions of various test plants artificially inoculated with
Pseudomonas solanacearum from abaca. Numbers indicate number of in-
fected plants over number of plants inoculated.


ISOLATES
Host Plant D Control
DES2 DES13 TA3 MT1 MT3 MT10


Banana
Giant Cavendish
Lakatan
Latundan
Butuhan

Abaca

Heliconia latispatha
Ginger
White potato
Castor bean
Peanut
Cowpea
Eggplant


0/4 0/4 0/4 0/4 0/4 0/4
0/2 0/2 0/2 0/2 0/2 0/2
0/2 0/2 0/2 0/2 0/2 0/2
0/2 0/2 0/2 0/2 0/2 0/2

4/4 4/4 4/4 4/4 4/4 4/4

0/4 0/4 0/4 0/4 0/4 0/4
0/4 0/4 0/4 0/4 0/4 0/4
4/4 4/4 4/4 4/4 4/4 4/4
6/6 6/6 6/6 6/6 6/6 6/6
0/4 0/4 0/4 6/6 6/6 6/6
0/4 0/4 0 /4 04 0/4 0/4


Dumaguete Long Purple 3/4 4/4 3/4 4/4 4/4 4/4
Black Beauty 1/2 1/2 2/2 2/2 2/2 2/2


Tomato
2029
Improved Harbot

Tobacco
Vizbur
Bottom Special


0/8 0/8 0/8 6/6 6/6 6/6
4/4 3/4 3/4 4/4 4/4 4/4


3/4 4/4 2/4 0/4 0/4 0/4
0/4 0/4 0/4 0/4 0/4 0/4


Jan. & June 1982









Philippine Phytopathology


Table 2. Summary of the reactions of various test plants naturally inoculated with
Pseudomonas solanacearum from abaca. Numbers indicate number of in-
fected plants over number of plants inoculated.

ISOLATES
Host Plant
HostPlant DES2 DES 13 TA3 MT1 MT3 MT10 Control


Banana
Giant Cavendish 0/4 0/4 0/4 0/4 0/4 0/4 0/4
Lakatan 0/3 0/3 0/3 0/3 0/3 0/3 0/3
Latundan 0/3 0/3 0/3 0/3 0/3 0/3 0/3
Butuhan 0/3 0/3 0/3 0/3 0/3 0/3 0/3

Abaca 0/3 0/3 0/3 0/3 0/3 0/3 0/3

Heliconia latispatha 0/4 0/4 0/4 0/4 0/4 0/4 0/4
Ginger 0/5 0/5 0/6 0/5 0/5 0/5 0/4
White potato 0/3 0/3 0/3 0/4 0/4 0/4 0/4
Castor bean 0/8 0/8 0/8 2/8 2/8 2/8 2/8
Peanut 0/10 0/10 0/10 0/10 0/10 0/10 0/8
Eggplant
2029 0/10 0/10 0/10 1/10 3/10 2/10 0/10
Tobacco
Bottom Special 0/10 0/10 0/10 0/10 0/10 0/10 0/10
Pepper 0/10 0/10 0/10 0/10 0/10 0/10 0/10


LITERATURE CITED

BUDDENHAGEN, I.W. 1961. Bacterial wilt of bananas: history and known distribution.
Trop. Agr. (London) 38: 107-121.
BUDDENHAGEN, I.W., L. SEQUIERA & A. KELMAN. 1962. Designation of races in
Pseudomonas solanacearum. Phytopathol. 52: 726 (Abstr).
CALINISAN, M.R. 1938. Vascular disease of abaca (Manila Hemp) in Davao. Philipp.
Jour. Agr. 9: 153-157.
QUIMIO, A.J. 1976. Semi-Annual Report. Abaca Research and Extension Program. UP
at Los Banos, Philippines.
REVILLA, M.V. & L.A. VARGAS. 1968. Bacterial wilt of banana in Peru. Trop. Abst.
23:310.
ZEHR, E.I. 1970. Isolation of Pseudomonas solanacearum from abaca and banana in the
Philippines. PI. Dis. Reptr. 54: 516-520.
ZEHR, E.I. 1970. Strains of Pseudomonas solanacearum in the Philippines as determined
by cross-inoculation of host at differential temperatures. Philipp. Phytopathol. 6:
45-54.


Vol. 18









Philipp. Phytopathol. 18: 61-67


EFFECTS OF FIVE NEMATICIDES ON THE CONTROL OF
NEMATODES AND YIELD OF TOMATO

R. G. DAVIDE and R. A. ZORILLA

Respectively, NCPC Deputy Director, Professor and Research Assistant, Depart-
ment of Plant Pathology, University of the Philippines at Los Banos, College, Laguna
Supported by a research grant from the National Crop Protection Center as a part
of its Vegetable Pests Management Program.

ABSTRACT

Nemacur 10G, Temik 15G, Furadan 3G, Mocap 5G and Vydate 10G using 10,
7.5, 4.5, 10 and 10 kg. a.i./ha., respectively, greatly reduced root-knot nematode (M.
incognita) infection in tomato. Population densities of other plant parasitic nematodes
were also affected by the nematicide treatment. As a result of the nematode control,
a highly significant yield increase was obtained ranging from 6 to 122%, 40 to 96% and
28 to 109% in the 1979, 1980 and 1981 trials, respectively, using tomato var. VC
11-1. The highest yield increase of 121.65% resulted from Nemacur 10G treatment,
followed by Temik 15G, Furadan 3G, Vydate 10G and Mocap 5G treatments.


Tomato is widely grown in South-
ern and Central Luzon and in the Visayas
and Eastern Mindanao. The 1974 report
of the Bureau of Agricultural Economics
showed that 16,750 hectares in the Phil-
ippines are planted to tomato with yield
varying from 2 to 12 tons per hectare.
Pest and disease problems are among the
factors responsible for this wide variation
in yield. It has been demonstrated that
tomato plants are susceptible to nematode
attack particularly the root-knot nema-
tode, Meloidogyne incognita, resulting in
significant yield reduction (Lear and Tho-
mason, 1956; Madamba et al., 1967;
de la Rosa and Davide, 1969; Ferrer et
al., 1972 and Kyron, 1973). In a field ex-
periment conducted by Ducusin and Da-
vide (1972) results showed that a number
of nematicides can effectively control
M. incognita on tomato with a significant
increase in yield.
This study was conducted to de-
termine the effectiveness of five nemati-
cides, namely: Nemacur 10G, Temik


15G, Furadan 3G, Vydate 10G and Mo-
cap 5G against M. incognita and other
nematodes associated with tomato and to
evaluate their effects on yield.


MATERIALS AND METHODS

The experiments were conducted in
the Experiment Station of the UPLB-
College of Agriculture. The area was di-
vided into 1 x 4 meters subplots. A 50-cm
space was provided between plots. Using
a randomized block design with five
replications, the following nematicides
were tested: Nemacur 10G (10% 0,
ethyl-0 (3-methyl 4 methylthiophenyl)-
isopropylamidophosphate), Temik 15G
(15% 2-methyl-2 (methylthio) propional-
dehyde 0- (methylcarbamoyl)oxime),
Vydate 10G (10% S-methyl1 /dimethyl
carbamoyl/ -N- / (methyl carbamoyl) /
thioforminidate), Furadan 3G (3%, 2,
3-dihydro 2,2-dimethyl-7-bensofuranyl
methyl carbamate) and Mocap 5G (5%









Philippine Phytopathology


0-ethyl S,S, dipropyl phosphorodithioate),
Nemacur 10G and Mocap 5G were used
at 80 g per 4 sq. m. plot while Temik
15G, Vydate 10G and Furadan 3G were
used at 20, 40, and 60 g sq. m. plot, res-
pectively. Each chemical was evenly
spread and incorporated into top 8 cm
soil a day before planting the test plants.
For pre-treatment determination of the
soil nematode population, a total of 400
cc soil samples were collected from 3 sites
per plot and after treatment, subsequent
sampling was done at monthly intervals
until harvest.
A day after treatment, each plot
was planted with 6-week old tomato
seedling var. VC 11-1 grown in small plas-
tic bags where each plant was inoculated
with two egg masses ofM. incognita be-
fore planting to insure uniform infection
of the plants. Each treatment including
the control was replicated five times
and each replicate plot had a row of to-
mato planted at 30 cm apart. Each row
contained eight plants. Throughout the
growing period, the plants were regular-
ly fertilized with ammonium sulfate
(21-0-0) and complete fertilizer (14-
14-14) and sprayed periodically with the
recommended rate of insecticide Sevin
or Thiodan and fungicide Benlate to pre-
vent insect attack and fungal infection.
All soil samples collected were processed
for nematodes in the Nematology labo-
ratory using the sieving-Baermann funnel
method. To determine the degree of
root-knot nematode infection after har-
vest, each plant was carefully uprooted
and root gall index was taken as follows:
1 for no gall; 2 for trace (1-25%), 3 for
slight-(26-50%), 4 for moderate (51-75%)
and 5 for severe (76-100%). The effect
of the treatment on yield was determined
by getting the total weight of mature
fruits at harvest time. The data obtained


were summarized and statistically analyzed
for significance test among treatment
means. The study consisted of three
trials from January 1979 to May 1981.

RESULTS AND DISCUSSION

Effects of the treatment on root-
knot nematode infection The mean
gall index ratings of the plants in three
trials clearly indicate that the nematicidal
treatments had considerably reduced the
root-knot nematode infection (Table 1).
Generally, the mean gall index ratings of
the plants in three trials followed the same
trends. The plants treated with Nemacur
10G and Temik 15G gave trace infection
as shown by low gall indices (1.5 and
1.9) and more plants showed no galls.
Vydate 10G, Mocap 5G- and Furadan
3G-treated plants had slight galling. The
control plants showed moderate to se-
vere infection. Results in the three trials
indicate that gall index rating taken at
the completion of the experiments ge-
nerally showed no relationship with the
yield increase in some treatments, par-
ticularly those of Mocap 5G and Vydate
10G. Although, the chemicals exhibited a
long lasting effect on the nematode,
the plants did not give optimum yield
performance which may be due to phyto-
toxicity. The relatively high galling index
in some treatment particularly that of
Furadan and Vydate may be due to se-
cond and possibly third generation nema-
tode infection upon which the chemicals
may have already less residual effect
(Davide, 1979).

Effect on other plant parasitic
nematodes Evidently, all the nemati-
cide treatments greatly reduced the
populations of other genera of plant para-
sitic nematodes (Table 2). Among the


Vol. 18









Effects of nematicides on nematodes and yield of tomato


treatments, Nemacur 10G and Temik
15G were superior while Furadan 3G
gave the highest nematode counts parti-
cularly during the third month but this
is still lower as compared with the con-
trol.

Effect of the treatment on yield -
The data summarized in Table 3 general-
ly showed highly significant increase in
yield of the nematicide-treated plants as
compared with those of the control
plants. In the first trial the highest yield
increase in Nemacur 10G was 122%,
whereas in the second and third trial, the
highest increase of the same treatment
using the same variety was 96% and 109%,
respectively. Temik 15G-treated plants
showed a yield increase of 66-83%, Fu-


radan 3G-treated plants gave 53-98% while
Vydate 10G-treated plants showed 27-
60% and Mocap 5G-treated plants gave
5-50% yield increase. Based on the ne-
matode control and subsequent yield
increase, Nemacur 10G and Temik 15G
were the superior treatments followed by
Furadan 3G, Vydate 10G and Mocap
5G. However, there was no significant
mean yield difference between Mocap 5G
and Vydate 10G in the first, second and
third trials, respectively. All the chemicals
tested namely: Temik, Mocap, Furadan
and Nemacur have been shown abroad
to be also effective against M. incognita
on tomato resulting in significant yield
increase (Johnson, 1978 and McCleod,
1977).


Table 1. Effects of nematicide treatments on root-knot nematode infection on tomato
var. VC 11-1 based on gall index of three trials conducted during the dry sea-
son of 1979, 1980 1981.

TREATMENT RATE TRIAL AND MEAN GALL INDEXa
(kg a.i./ha) I II III

NEMACUR 10G 10.0 2.17 1.48 1.47
TEMIK 15G 7.5 2.24 1.88 1.95
FURADAN3G 4.5 2.86 3.07 3.15
VYDATE 10G 10.0 3.31 2.83 2.47
MOCAP 5G 10.0 3.37 2.95 2.97
CONTROL No Treatment 4.40 4.90 4.90


a The gall index rating are as follows: 1 for no gall; 2 for trace (1-25%); 3 slight
(26-50%); 4 for moderate (51-75%) and 5 for severe (76-100%). Data for each trial are
means of 5 replications.


Jan. & June 1982









Philippine Phytopathology


Table 2. Mean nematode counts before and after soil treatment with nematicide on to-
mato variety VC 11-1 based on 400 cc soil samples. a

NEMATODE COUNTS PER 400 CC SOILS
TREATMENT AND
NEMATODE GENUS BEFORE AFTER TREATMENT
TREATMENT 1st month 2nd month 3rd month


NEMACUR 10G
Meloidogyne b
Rotylenchulus
Pratylenchus
Helicotylenchus
Criconemoides
Xiphinema


VYDATE 10G
Meloidogyne
Rotylenchulus
Pratylenchus
Helicotylenchus
Criconemoides
Xiphinema


MOCAP 5G
Meloidogyne
Rotylenchulus
Pratylenchus
Helicotylenchus
Criconemoides
Xiphinema


FURADAN 3G
Meloidogyne
Rotylenchulus
Pratylenchus
Helicotylenchus
Criconemoides
Xiphinema


484.4
7.2
4.6
8.6
3.2
7.2
Total- 505.6


488.0
7.6


Total- 517.6


402.0
6.8


Total 428.2


520.2
6.8
7.2
4.0
1.8
8.8
Total- 544.6


23.2
2.6
1.4
3.6
1.0
4.0
35.8


32.2
2.4
1.8
2.0
1.2
5.6
45.2


27.2
5.4
2.2
3.8
2.0
3.6
44.2


33.0
6.6
3.8
3.4
2.8
7.0
56.6


45.0
5.4
3.4
4.2
1.6
5.4
65.0


59.4
6.6
5.6
3.0
1.6
4.8
80.4


25.2
6.4
1.8
3.4
1.6
3.6
42.0


48.8
6.6
5.0
3.2
2.0
7.2
72.8


44.4
5.6
3.8
3.8
2.0
6.0
65.6


133.4
6.0
6.8
2.8
2.0
6.4
157.0


57.4
5.0
3.0
3.2
0.4
1.2
69.8


Vol. 18









Effects of nematicides on nematodes and yield of tomato


Table 2. cont'd...

NEMATODE COUNTS PER 400 CC SOILS

TREATMENT AND
NEMATODE GENUS BEFORE AFTER TREATMENT
TREATMENT 1st month 2nd month 3rd month



TEMIK 15G
Meloidogyne 487.2 13.2 27.2 24.8
Rotylenchulus 8.8 2.0 4.2 2.8
Helicotylenchus 3.0 1.2 2.0 4.4
Criconemoides 5.8 3.4 3.8 2.2
Xiphinema 3.6 2.2 1.8 1.6
8.6 1.6 2.0 4.2
Total- 517.0 24.6 41.0 40.0

CONTROL
Meloidogyne 484.4 595.0 776.0 855.8
Rotylenchulus 5.2 7.0 13.2 6.2
Pratylenchus 4.6 5.4 15.0 10.0
Helicotylenchus 8.2 9.0 14.2 11.8
Xiphinema 1.2 4.2 6.2 5.4
6.8 7.0 8.2 8.2
Total- 510.0 628.6 832.8 897.4


a Data are means of 5 replication from third trial. The first and second showed
similar trend of results.


b Second stage larvae.


Jan. & June 1982









Philippine Phytopathology


Table 3. Effects of nematicide treatments on yield (Kg) of tomato var. VC 11-1 during
dry seasons of 1979, 1980 and 1981.


TRIALS


TREATMENT



NEMACUR 10G
TEMIK 15G
FURADAN 3G
VYDATE 10G
MOCAP 5G
CONTROL


RATE
(kg a.i./ha)

10.0
7.5
4.5
10.0
10.0
No Treatment


I
1979
4.8a
3.9a
4.2a
2.8 b
2.3 b
2.2 b


Increase
(%)
121.6
82.5
98.2
26.7
5.5


II
1980
13.4a
11.4ab
10.9 b
10.9 b
9.5 b
6.8 c


Increase III
(%) 1981
96.0 7.5a
66.5 6.6ab
53.4 5.9 b
60.5 5.4 b
39.8 4.6 b
3.6 c


a Data of each trial are means of five plot replicates.

b Means followed by the same letters in a column are not significantly different
at 5% level with DMRT.


Increase
(%)
108.9
82.7
63.2
50.4
28.1


Vol. 18









Effects of nematicides on nematodes and yield of tomato


LITERATURE CITED

DAVIDE, R. G. 1979. Effects of nematicides and Tagetes erecta on the control of Me-
loidogyne incognita and on yield of tomato. Philipp. Phytopathol. 15: 141-144.

DUCUSIN, A. R. and R. G. DAVIDE. 1972.Meloidogyne incognita. Its effect on tomato
yield and some method of control. Philipp. Agr. 55: 261-281.

ROSA, DELA A. G. and R. G. DAVIDE. 1969. Pathogenecity test of four genera of
plant parasitic nematodes on vegetable crops. Philipp. Phytopathol. 5: 29-38.

FERRER, COLON M., AYALA, A. and D. CUEVAS. 1972. Preliminary result of an ex-
periment with enmaticides for the control of nematode attacking tomato in sandy
soil. Nematropica 2(1): 16-17.

JOHNSON, A. W. 1978. Effect of nematicide application through overhead irrigation on
control of root-knot nematodes on tomato transplants. Plant Dis. Reptr. 62: 48-51.

KYROU, N. C. 1973. Effect of soil treatments on root-knot nematodes affecting fresh
fruits and canning tomatoes in California. Plant Dis. Reptr, 57: 1033-1035.

LEAR, B. and I. J. THOMASON. 1956. Control by soil fumigation of rootknot nema-
todes affecting fresh fruits and canning tomatoes in California. Plant Dis. Reptr.
40(11): 981-988.

MADAMBA, C. P., GOSECO, G.G., DEANON, J. R. Jr. G. B. 1967. Yield responses of
some vegetable and field crops to soil fumigation for the control of plant parasitic
nematodes. Philipp. Agr. 50: 804-816.

McLEOD, R. W. 1977. Control of root-knot in tomatoes; Trials with granular nematicide.
Agr. Gasette New South Wales 88: 38-41.


Jan. & June 1982









Philipp. Phytopathol. 18: 68-77


SORGHUM GRAIN MOLDS: IDENTIFICATION, INCIDENCE
AND PATHOGENICITY

MARIA P. DAYAN and S. C. DALMACIO

Respectively, former Graduate Student and Assistant Professor, Department of
Plant Pathology, College of Agriculture, University of the Philippines at Los Banos,
College, Laguna.
Portion of a Master of Science thesis of the senior author.
This study was supported by the National Science Development Board (NSDB),
now the National Science and Technology Authority (NSTA).

ABSTRACT

Twenty fungal genera were found associated with sorghum grains at harvest.
These include: Alternaria, Arthrobotrys, Aspergillus, Botryodiplodia, Cephalospo-
rum, Cladosporium, Curvularia, Colletotrichum, Fusarium, Gleocercospora, Helmin-
thosporium, Nigrospora, Phaetrichoconis, Penicillium, Pestalotia, Phoma, Phomopsis,
Rhizopus, Rhizoctonia and Trichoconis. The fungal genera consistently observed in all
tests in decreasing order were: Fusarium, Curvularia, Phoma, Penicillum and Helmin-
thosporium. Fusarium moniliforme and Curvularia lunata were the most predominant
species observed.
F. moniliforme and C. lunata showed higher infection during the wet season.
The two fungi invaded both the embryo and endosperm, thereby, reducing seed via-
bility. F. moniliforme appeared more aggressive than C. lunata.


Grain mold refers to the diseased
appearance of sorghum grain resulting
from the infection of the developing grain
by one or more parasitic fungal species
(Williams and Rao, 1980). Severely in-
fected grains may appear completely
covered with pink or black mold and dis-
integrate into powder in the threshing
process. On the other hand, lightly infec-
ted grain may appear almost completely
normal except for slight discoloration on
a small portion of the surface.
Sorghum breeders and pathologists
from Africa, Asia, and the Americas con-
sidered grain molds as one of the major
diseases and research problems in the
improvement of the sorghum crop
(Williams and Rao, 1980). This may
have resulted from the development and
release of high-yielding, short-duration,


nonphotosensitive varieties that mature
during wet weather, hence, vulnerable to
attack by grain mold pathogens.
As many as 32 genera fungi have
been reported to be associated with
sorghum grains (Williams and Rao, 1980).
The incidence of these fungi may vary
from one country or locality to another.
The most frequently encountered genera
were: Fusarium, Curvularia, Altemaria,
Aspergillus and Phoma.
In the Philippines, particularly in
Luzon, grain molds have been commonly
observed during the wet season. It is not
unusual to observe maturing sorghum
heads completely covered with molds
(Fig. 1) hence, one way of avoiding grain
mold would be to plant sorghum only
during the dry season. Planting sorghum
during the dry season would also take


Vol. 18









Sorghum grain molds


Fig. 1. Sorghum head completely covered with head mold fungi.


advantage of the crop's ability to to-
lerate limited water supply better than
any dry season crop. On the other hand,
major sorghum growing areas in the Phil-
ippines have even distribution of rainfall
(Type 4 rainfall pattern) so that rain du-
ring crop maturity cannot be avoided.
Since the use of chemicals to control


grain, molds would pose hazard to ani-
mals, the most appropriate approach
would be the use of varieties/hybrids with
adequate resistance to grain mold infec-
tion. As a first step towards this end, fungi
associated with sorghum grains must be
identified and their relative importance
ascertained; hence, this study.


Jan. & June 1982









Philippine Phytopathology


MATERIALS AND METHODS

Mature sorghum seeds of different
genotypes were collected at harvest
time, dried and placed in individual coin
envelopes prior to sampling. One hundred
seed samples of each variety were tested
using Agar Plate test and Blotter test. In
the Agar Plate test, seeds were soaked
in 1% sodium hypochlorite (Na0C1)
solution for 10 min, rinsed with sterile
distilled water and seeded at the rate of
10 seeds each in plates containing 15-20
ml potato dextrose agar (PDA). For
Blotter test, seeds were sown in petri
dishes with moistened filter paper at 50
seeds per plate. Seeded plates were in-
cubated at 25-28C under 12 hr light-
dark cycle for one week.
The fungi associated with individual
sorghum seeds were examined under the
microscope, identified and recorded. Iden-
tification of the fungi was based on the
techniques employed by the International
Seed Testing Association (ISTA) for de-
veloping countries exemplified by the
works of Ram Nath et al. (1970) and
Benoit and Mathur (1970) on Fusarium
and Curvularia spp., respectively.
The pathogenicity ofF. moniliforme
and C. lunata were tested on sorghum at
flowering and soft dough stages. Spore
suspensions were prepared from sterilized
sorghum grains inoculated with pure cul-
tures of the fungi. Inoculated and non-
inoculated panicles were covered with
plastic bags for 48 hr and replaced with
tassel bags until reading was made 3
weeks after inoculation or at harvest time.
To determine the location of the
fungi in the seed, seeds from inoculated
panicles were soaked in 5% KOH for 30
min. Seeds were then dissected and em-
bryo was taken out. Embryos and endo-
sperms were then treated with 1% NaOC1


for 5 min, plated in PDA and incubated
at 25-28 C under alternate light and dark
condition for 7 days. Presence of the
fungi in the endosperm and embryo was
recorded.

RESULTS

A total of 20 fungal genera were
found associated with sorghum grains.
These include: Alteraria, Arthrobotrys,
Aspergillus, Botryodiplodia, Cephalospo-
rium, Cladosporium, Colletorichum, Cur-
vularia, Fusarium, Gleocercospora, Hel-
minthosporium, Nigrospora, Penicillicum,
Pestalotia, Phaetrichoconis, Phoma, Pho-
mopsis, Rhizoctonia, Rhizopus and Tri-
choconis. The frequencies of these fungal
genera varied with the trials. Fungal
genera that were consistently observed
and present in the order of decreasing
frequency were: Fusarium, Curvularia,
Phoma, Penicillum, and Helminthospo-
rium (Table 1).
Fusarium and Curvularia were the
most predominant fungal genera found
associated with sorghum grains, account-
ing for about 84% of all infected seeds
(Fig. 2). Two species each were identi-
fied, namely: F. moniliforme and F. se-
mitectum (Fig. 3) for Fusarium and C.
lunata and C. pallescens (Fig. 3) for
Curvularia. F. moniliforme was found in
85 and 84% of allFusarium-infected seeds
during the wet and dry seasons, respec-
tively.
Results of inoculation studies with
F. moniliforme and C. lunata are summa-
rized in table 2. Although non-inoculated
heads produced infected grains, the effect
of inoculation is quite evident. Inocula-
tion of sorghum heads at flowering showed
higher infection by the two fungi when
compared to inoculation at soft-dough
stage. Results also showed higher infec-


Vol. 18









Sorghum grain molds


Fig. 2. Sorghum kernels infected with Fusarium and Curvularia spp.


Jan. & June 1982









Philippine Phytopathology


Fig. 3. Photomicroprahs showing A) microconidia of F. moniliforme (1525X), B)
macroconidia ofF. semitectum (645X), C) conidia of C. lunata (51OX), D)
conidia of C. pallescens (983X).


Vol. 18









Sorghum grain molds


Table 1. Frequency of
harvest.


fungal genera consistently associated with sorghum grains at


TRIAL
GENERA
Ia IIb IIIc IVc TOTAL

Fusarium 315 1197 1808 527 3847
Curvularia 274 202 718 454 1648
Phoma 210 110 23 10 353
Penicillium 91 25 99 12 227
Helminthosporuim 23 19 21 15 78


aBased on 1,700 grains from 17 different sorghum lines.
bBased on 3,500 grains from 35 different sorghum lines.

CBased on 5,000 grains from 50 different sorghum lines.





Table 2. Disease rating of sorghum heads inoculated with F. moniliforme and C. lunata
at flowering and soft-dough stages.


Flowering


Wet Season
Noninoculated
Control
F. moniliforme
C. lunata
Dry Season
Noninoculated
Control
F. moniliforme
C. lunata


Mean


Mean


2.36a
4.11
3.88
3.45


1.18
2.33
2.07
1.86


Soft-dough


1.98
3.58
3.66
3.07


aAverage rating of 50 sorghum lines; 5 heads per line. Rating of 1 = 1-20% head dis-
coloration; 2=21-40%; 3=41-60%; 4=61-80% and 5=81-100% head discoloration.


Jan. & June 1982









Philippine Phytopathology


Table 3. Effect of F. moniliforme and C. lunata on seed viability of sorghum inoculated
at flowering and soft-dough stages.

Flowering Soft-dough Mean

Wet Season
Noninoculated
Control 68.38 a 84.9 76.64
F. moniliforme 48.02 58.90 53.46
C. lunata 45.08 55.00 50.04
Mean 53.83 66.27 60.04

Dry Season
Noninoculated
Control 87.08 88.12 87.60
F. moniliforme 71.72 71.80 71.76
C. lunata 71.88 76.06 74.97
Mean 76.89 78.66 78.11



a Percent germination of mature sorghum seeds harvested from heads inoculated with
F. moniliforme and C. lunata at flowering and soft-dough stage.


tion during the wet as compared to the
dry season. Furthermore, F. moniliforme
appeared more aggressive than C. lunata
when inoculation was done at flowering
but not at soft-dough stage.
F. moniliforme and C. lunata were
found to colonize both the embryo and
endosperm. The frequency of occurrence
of both fungi was much higher in the en-
dosperm than in the embryo. F. monili-
forme was observed in 87% of the endo-
sperm as compared to 43% of the embryo
samples examined. Likewise, C. lunata was
observed in 47% and 10% of the endos-
perm and embryo samples examined,
respectively.
Infection of the endosperm and
embryo is reflected by the reduced via-
bility of sorghum seeds (Table 3). As ex-
pected, seed viability was lower during


the wet season and when inoculation was
done at flowering. During the 1979
wet season, non-inoculated control, F.
moniliforme- and C. lunata-inoculated
heads at flowering gave 68, 48 and 45%
germination, respectively. On the other
hand, non-inoculated control, F. mo-
niliforme-and C lunata-inoculated heads
gave 87, 71 and 72% germination, respec-
tively, during the 1980 dry season.

DISCUSSION

The association of a number of fun-
gal genera as found in the present study
confirmed the results of studies in other
countries. Rao and Williams (1980)
isolated 17 fungal species in 11 genera
from field-collected molded sorghum
grains. Williams and Rao (1980) also enu-


VoL 18









Sorghum grain molds


merated as many as 32 different genera
of fungi associated with moldy grains as
reported by various investigators. Among
these fungal genera, the following appeared
most frequently associated with moldy
grains: Fusarium, Curvularia, Alteraria,
Aspergillus, Phoma and Trichotecium
(Mathur et al., 1967; Williams and Rao,
1980; Rao and Williams, 1980). Likewise,
Castor and Frederiksen (1980) found that
Fusarium and Curvularia were the most
important grain molds in Texas.
The presence of Alternaria and As-
pergillus in less frequency may be attribu-
ted to the type of samples used. In the
present study, only newly harvested sorg-
hum grains were used. Hence, Dalmacio
and Dayan (1977) found that Aspergillus
predominated over Fusarium in samples
that have been collected or used long after
harvest. Seitz et al., (1975) found that
the presence of field fungi may also in-
hibit the development of storage fungi
like Aspergillus spp. This may also ex-
plain the present results since seeds were
tested right after harvest. On the other
hand, 7 fungal genera reported in the pre-
sent study have not been observed else-
where. This may be attributed to diffe-
rences in the native microflora which may
be influenced by the vegetation in the
surrounding fields and the local environ-
mental conditions.
The abundance of grain molds du-
ring the wet season is also consistent with
the observations of other workers abroad.
It is generally accepted that wet weather
following flowering is necessary for grain
mold development and the longer the wet
period the greater the mold development.
Dry weather during flowering and grain
development followed by wet weather
near maturity will not promote serious
mold infection as when wet weather oc-
curs from the time of flowering onward


(Kateswar Rao and Poormachandrudu,
1971; Gray et al., 1971; Rao and Wil-
liams, 1980; and Williams and Rao,
1980). Castor and Frederiksen (1980)
stated that the presence of heavy rain does
not only favor fungal growth of the or-
ganisms but also delays harvest which in
turn prolong the disease cycle. The latter
observations may also explain the higher
incidence of grain molds when inocu-
lation was done at flowering time. Sorg-
hum heads inoculated earlier are subjected
to colonization by both fungi for a longer
period of time.
The aggressiveness ofF. moniliforme
as demonstrated in the present study
also supports the findings of Castor and
Frederiksen (1980) in Texas, U.S.A. On
the other hand, studies at International
Crops Research in the Semi-Arid Trophies
(ICRISAT) showed that C. lunata was
more damaging than F. moniliforme.
Such discrepancy may be attributed to
the environmental conditions as well as
the varieties used. Hence, lines such
as SC 0103 and SC 0748 may be more
damaged by Curvularia spp than by
Fusarium spp. (Castor and Frederiksen,
1982). This was also observed in the
present study where sorghum line CS 264
showed higher infection rating for C.
lunata than for F. moniliforme.
The reduced viability of sorghum
seeds may be attributed to the ability of
the fungi to invade both the endosperm
and the embryo. Mathur et al., (1975) re-
ported that F. moniliforme initially colo-
nizes the scuttellar region. Such proximity
to the embryo could easily explain the re-
duced germination of infected seeds.
Glueck (1979) has observed that C.
lunata enters the kernel along with the
uptake of water which enters primarily
through the hilar end. Since embryo is
near the hilar end the fungus infects


Jan. & June 1982









Philippine Phytopathology


the surrounding cells of the embryo
thus reducing seed germination.
In view of the importance of F.
moniliforme and C. lunata in grain mold
problem, screening for resistance to grain
mold should be directed against these
pathogens. The Philippines would be a
suitable site for grain mold resistance
screening because of favorable environ-


mental conditions during the rainy season
and the natural abundance of inoculum.
Hence, in recent trials at College, Laguna
using yellow-seeded sorghum hybrids
from ICRISAT, serious incidence of grain
molds, primarily F. moniliforme, C. lu-
nata and Phoma spp. was encountered
without artificial inoculation.


REFERENCES

BENOIT, M.A. and S.B. MATHUR. 1970. Identification of species of Curvularia on rice
seed. Proc. Int'l Seed Test. Assoc. 35:99-119.

CASTOR, L. L. and R. A. FREDERIKSEN. 1980. Fusarium and Curvularia grain molds
in Texas. In ICRISAT, Proc. Int'l. Workshop on Sorghum Diseases, 11-15 Dec.
1978, Hyderabad, India.

CASTOR, L. L. and R. A. FREDERIKSEN. 1982. Grain deterioration in sorghum. In
ICRISAT, Proc. Int'l Symp. on Sorghum Grain Quality, 28-31 October 1981, Pa-
tancheru, A. P., India.

DALMACIO, S. C. and M. M. dela PENA. 1977. Seed-borne diseases of major crops in
the Philippines. Terminal Research Report, College, Laguna.

GRAY, E. G., D. LACEFIELD and J. Q. LAWE. 1971. Head mold on grain sorghum.
Pit. Dis. Reptr. 55(4): 337-339.

GLUECK, J. A. 1979. Studies on sorghum head mold caused by C. lunata. Seed Sci. and
Tech. 7:535.

KATESWAR RAO, G. and POORNACHANDRUDU. 1971. Isolation of head molds and
assessment of moldy grains in certain sorghum varieties. The Andhra Agr. J. 18(4):
153-156.


MATHUR, S. K., MATHUR, S. B. and P. NEERGARD. 1975. Detection of seed-borne
fungi in sorghum and location of Fusarium moniliforme in the seed. Seed Sci and
Tech. 3:683-690.


Vol. 18









Jan. & June 1982 Sorghum grain molds 77


RAM NATH, P. NEERGARD and S. B. MATHUR. 1970. Identification of Fusarium
species on seeds as they occur in Blotter test. Proc. Int'l Seed Test. Assoc. 35:121-
144.

RAO, K.M. and WILLIAMS, 1980. Screening for sorghum grain mold resistance at
ICRISAT. In ICRISAT, Proc. Int'l. Workshop on Sorghum Diseases, 11-15, Dec.

SEITZ, L. M., D. B. SAVER, H.E. MOHR and R. BURROUGHS. 1975 Weathered
grain sorghum, natural occurrence of altemariols and storability of the grain.
Phytopath. 65: 1259-1263;

WILLIAMS, R. J. and K. N. RAO. 1980. A review of sorghum grain molds. In ICRISAT,
Proc. Int'l Workshop on Sorghum Diseases, 11-15 Dec. 1978, Hyderabad, India.









Philipp. PhytopathoL 18: 78-88


SWEET POTATO SUCROSE AGAR AN INEXPENSIVE
CULTURE MEDIUM FOR FUNGAL GROWTH

LINA L. ILAG, ARACELI R. PUA and VICTORIA A. MARFIL

Associate Professor, Research Associate and Research Assistant respectively,
Department of Plant Pathology and Institute of Plant Breeding, College of Agriculture,
U.P. at Los Banos, College, Laguna, Philippines.


The authors are grateful to Mrs. Angelina R. Gabriel for technical
assistance.

ABSTRACT

Sweet potato sucrose agar or SPSA (composed of sweet potato, 200 g; sucrose
from brown cane sugar, 17 g; agar bar or "gulaman", 15 g; tap water allowed to stand
for 24 hours, to make one liter) was found to be an excellent substitute for potato
dextrose agar (PDA).
Seven test fungi exhibited better mycelial growth and higher sporulation in
SPSA than in PDA. The fungi tested were Stemphylium lycopersici (Enjoji) Yam,
Colletotrichum gloeosporioides Penz., Pythium debaryanum Hesse, Rhizopus nigri-
cans Ehr., Aspergillus flavus Lk. ex Fries, Volvariella volvacea (Bill. ex Fr.) Sing. and
Fusarium moniliforme Sheldon.
SPSA not only supported good fungal growth, its ingredients are inexpensive and
are readily available locally.


INTRODUCTION

The Philippine government spends mil-
lions of pesos each year for research.1
As the cost of labor, supplies, materials,
equipment and everything else continues
to rise, it is about time for responsible
and concerned scientists to find ways of
reducing the cost of research. It is to-
wards this end that this study was
conducted to find a cheap, readily
available and effective medium for the
growth of plant pathogens.
At present, the culture medium that
is most widely used for the isolation,
maintenance and storage of fungi is po-
tato dextrose agar (PDA) which is com-
posed of white potato, dextrose, pow-
dered agar, and distilled water. In this

I/PCARR. 1981. List of Researches by
Priority Area. Philippine Council for Agri-
culture and Resources Research. Los Banos,
Laguna.


study we determined the possibility of
substituting sweet potato for white po-
tato, sucrose from cane sugar for dex-
trose, the local agar bar or "gulaman"
for the imported powdered agar, and
rain or tap water for distilled water.

MATERIALS AND METHODS

Mycelial growth and sporulation

Potato dextrose agar (PDA) was pre-
pared and sterilized for 15 minutes at 121
C in a pressure cooker. PDA consisted of
a filtered decoction from 200 g white
potato; dextrose, 20 g; powdered agar
(Japanese brand), 17 g; distilled water, to
make 1 liter. The initial sweet potato
sucrose agar (SPSA) medium tested con-
sisted of sweet potato, 200 g; sucrose
(white table sugar), 17 g; agar bar ("gula-
man"), 15 g; rain water, to make one
liter. It was prepared and sterilized in
the same manner as PDA. The media









Sweet potato sucrose agar


were plated and separately seeded with
Fusarium moniliforme Sheldon,
Volvariella volvacea (Bill. ex. Fr.) Sing.
and Rhizopus nigricans Ehr. The colony
diameter of the cultures were measured
for the next seven days. The number of
spores formed in the different media were
determined with a haemacytometer 7
days after seeding.
All plates were incubated at room tem-
perature (19-30 C).

Effect of sucrose source in SPSA

SPSA was prepared as above except
that instead of using white table sugar as
the sucrose source, brown sugar or "pa-
nocha" was substituted. Mycelial expan-
sion and sporulation were determined as
in the previous experiment.

Effect of water source in SPSA

The SPSA used in this study consist-
ed of sweet potato, brown sugar and agar
bar or "gulaman" as before with only the
water source varied. Rain water, water
fresh from the tap, and tap water allow-
ed to settle for 24 hours were tested for
their comparative ability to support fun-
gal growth.

Effect of sweet potato varieties in SPSA

SPSA was prepared as before with 200
g sweet potato per liter of medium. Four
different cultivars of sweet potato were
tested to determine any variation in
growth and sporulation that may be at-
tributed to varietal differences. The
cultivars used were Rinagaygay (a local
promising variety), UPLB Ace. 225,
Kinabakab and VISCA Acc. 98. The
colony diameter and/or number of
spores formed by F. moniliforme, V
volvaceae and R. nigricans in the media
were determined.


Comparative mycehlal expansion and spo-
rulation in PDA and the standard SPSA

The mycelial growth and sporulation
of seven fungi were compared in the
usual PDA medium and what may be
called the improved or standard SPSA
medium. The standard SPSA is the cul-
minating medium which was not only
shown in previous experiments to be
highly capable of supporting luxuriant
mycelial growth and sporulation of
certain fungi but is also very inexpen-
sive to prepare. This medium is com-
posed of sweet potato, 200 g; brown
sugar, 17 g; agar bar or "gulaman", 15 g:
and tap water (1 liter) allowed to stand
for 24 hours.

RESULTS

Comparative mycelial growth and
sporulation of fungi in PDA and in the
initial SPSA tested

F moniliforme formed bigger colo-
nies in the initial SPSA medium than in
PDA seven days after seeding (Table 1).
V. volvacea grew more rapidly in SPSA
than in PDA as noted on the third day of
incubation. Further comparisons of
mycelial expansion were difficult to make
as growth completely filled and even-
tually overran both the SPSA and PDA
plates. Colony diameters of R. nigricans
in SPSA were smaller than in PDA.
F. moniliforme and R. nigricans produced
millions of spores per ml in both media.
F. moniliforme produced about the
same number of spores in both media
whereas R. nigricans sporulated better in
PDA (Table 1).


Jan. & June 1982









Table 1. Linear expansion and sporulation of three fungi in PDA (potato dextrose agar) and
initial SPSA (sweet potato sucrose agar)*.


Colony Diameter** (spores/ml
Day 3 Day 5 Day 7 (x 106)**
Fungi PDA SPSA PDA SPSA PDA SPSA PDA SPSA


Fusarium
moniliforme 34.5 d 36.3 d 61.8 d 63.8 d 79.8 c 84.7 b 2.9 c 2.0 c

Volvariella
volvacea 51.5 b 58.5 a 90.0 a 90.0 a plates were 0.0 0.0
overgrown
Rhizopus
nigricans 48.8 b 42.7 c 80.7 b 69.3 c 87.7 ab 79.3 c 7.5 a 4.4 b



PDA consisted of white potato, 200 g; dextrose, 20 g; powdered agar (Japanese brand), 17 g; distilled
water, to make 1 liter.

SPSA consisted of sweet potato, 200 g; white table sugar, 17 g; agar bar (gulaman), 15 g; rain water, to
make 1 liter.

**Average of 3 replicates; means with the same letter in each day of observation are not significantly
different at the 5% level by DMRT.









Sweet potato sucrose agar


Effect of sucrose source in SPSA

The test fungi grew rapidly in all the
sucrose sources tested. However, V. vol-
vacea exhibited the most rapid linear
growth of mycelia in SPSA with brown
sugar as the source of sucrose (Table 2).
Linear expansion was slightly slower
when white table sugar was used and
slowest in panochaa" F. moniliforme


also formed the largest colonies in brown
sugar and the smallest in panochaa"
as noted on the seventh day of incuba-
tion. Sporulation by this fungus on the
third day was least in SPSA with brown
sugar. However, on the seventh day,
essentially the same number of spores
were formed in the three sucrose sour-
ces (Table 2).


Table 2. Mycelial growth and sporulation in SPSA* (with different sources of sucrose).



Fungus/Sucrose Colony Diameter (mm)** Spores/ml (x106)**
Source Day 3 Day 5 Day 7 Day 3 Day 7

Fusarium moniliforme

white sugar 37.3 d 66.7 b 86.2 c 1.26 a 1.73 a
brown sugar 38.8 d 68.2 a 89.5 b 0.93 b 1.69 a
panochaa" 38.5 d 68.5 b 82.7 d 1.45 a 1.76 a

Volvariella volvacea

white sugar 59.5 b 90.0 a plates were overgrown
brown sugar 68.2 a 90.0 a plates were overgrown
panochaa" 52.8 c 90.0 a plates were overgrown

*SPSA composed of sweet potato, 200 g; sucrose (white, c brown, or panochaa"), 17 g;
agar bar ("gulaman'), 15 g;rain water to make 1 liter.
**Average of 3 replicates; means with the same letter in each day of observation are not
significantly different at the 5% level by DMRT.


Effect of water source

The mycelial growth of F. monilifor-
me was equally good in SPSA with rain
water and in the same medium with tap
water allowed to stand or settle for 24
hr (Table 3). Mycelial expansion was
inhibited in SPSA with fresh tap water.
Sporulation of the fungus did not differ


significantly in the three kinds of water.
V. volvacea, on the other hand, produced
on the third day of incubation the lar-
gest colonies in fresh tap water and the
smallest colonies in tap water allowed
to stand for 24 hours. Colony diameters
were, however, the same in the various
water sources five days after seeding
(Table 3).


Jan. & June 1982









Table 3. Mycelial growth and sporulation in SPSA* with different sources of water.


Fungus/Water Colony Diameter (mm)** Spores/ml (x105)**
Source Day 3 Day 5 Day 7 Day 3 Day 7

Fusarium moniliforme

rain water 33.8 d 58.7 b 83.8 b 6.75 a 9.75 a
fresh tap 30.0 d 51.3 d 68.3 c 7.75 a 13.60 a
tap water
allowed to
stand tor 24 hr 31.3d 55.0b 82.2b 7.25a 18.85a

Volvariella volvacea

rain water 60.0 b 90.0 a plates
overgrown

fresh tap water 68.1 a 90.0 a plates
overgrown

tap water allowed
to stand for
24 hr 52.8 c 90.0 a plates
overgrown



SPSA is composed of sweet potato, brown sugar, agar bar or gulaman and water from various sources.
** Average of 3 replicates; means with the same letter in each day of observation are not significantly
different at the 5% level by DMRT.









Sweet potato sucrose agar


Comparative fungal growth in PDA and
in standard SPSA

All the fungi tested (Stemphylium
lycopersici, Colletotrichum gloeosporioi-
des, V. volvacea, F. moniliforme, Py-
thium debaryanum, R. nigricans and
Aspergillus flavus) exhibited more rapid
mycelial expansion and higher sporula-
tion in standard SPSA than in PDA
(Table 4).

Effect of varieties on SPSA

The fungi tested differed in their
varietal preference for mycelial expan-
sion and sporulation. F. moniliforme
and R. nigricans grew and sporulated
best in UPLB Acc. 225 whereas V. vol-
vacea preferred Kinabakab (Table 5).
The least number of spores were formed
in VISCA Acc. 98. Nevertheless, all va-
rieties supported good mycelial growth of
the three fungi and varying degrees of
sporulation by F moniliforme and R.
nigricans.

DISCUSSION

This study shows that SPSA can subs-
titute for PDA as a general purpose la-
boratory medium for fungal growth. In
fact, compared to PDA, SPSA was shown
to provide better mycelial growth (Figs.
1-4) and sporulation of the fungi tested.
This is not surprising since sweet potato
contains more starch and food energy
as well as more vitamins and more mine-
rals than white potato The protein
content of sweet potato is less, although
varietal differences probably exist. Also,
the brown sugar and tap water used in
SPSA may contain various growth factors
not present in the dextrose and distilled


PARR. 1977. The Philippines Recom-
mends for Root Crops. Phil Council for Agric.
and Resources Research. Los Banos, Laguna.


water added to PDA. However, different
sources of tap water vary in their organic
and inorganic contents specially in the
kinds and amounts of minerals present.
It is best therefore, to perform a preli-
minary test on your water source if it is
being used as an ingredient in a culture
medium for the first time.
There is no reason to believe that a
microorganism grown in SPSA will
readily change in pathogenicity. An im-
perfect fungus grown in SPSA will not
suddenly go into a sexual stage and
hybridize, nor will it mutate in SPSA
any more or any less often than it would
in PDA.
A distinct advantage of SPSA over
PDA is the inexpensive ingredients the
former requires compared to those
needed for the latter. White potato is
four times more expensive than sweet
potato; dextrose is 7.85 times more ex-
pensive than table sugar; the imported
powdered agar is 1.8 times higher in cost
than the local agar bar (Table 6). The tap
water used in SPSA is not only cheaper
but is also more readily available than
distilled water. Moreover, SPSA requires
less sugar and less agar than PDA.
All the ingredients for SPSA are not
only less expensive but are also locally
available, nullifying the need to import
expensive media ingredients.


Jan. & June 1982









Table 4. Mycelial expansion and sporulation of various fungi in PDA and in standard SPSA.

Colony Diameter (mm)** Spores/ml (x103)**
Fungi Day 3 Day 5 Day 7 7th day
PDA SPSA PDA SPSA PDA SPSA PDA SPSA

Stemphylium 27.8 28.0 47.1 48.8 60.7 63.8 1.66 3.0
locepersici

Colletotrichum
gloeosporioides 27.9 32.7 36.1 53.8 41.3 71.6 160.00 194.0

Volvariella
volvacea 44.2 50.5 88.8 90.0 plates plates 0.0 0.0
over- over-
Fusarium grown grown
moniliforme 33.6 33.4 53.1 57.6 73.8 78.8 2035.0 2360.0

Pythium
debaryanum 90.0 90.0 plates plates plates plates 3.0 6.0
over- over- over- over-
grown grown grown grown

Rhizopus nigricans 32.9 33.3 48.8 54.3 58.8 69.1 1940.0 5065.0
Aspergillusflavus 28.0 28.7 44.0 46.2 55.3 60.3 5425.0 7785.0


**Average of 3 replicates.









Sorghum grain molds


Table 5. Mycelial growth and sporulation in SPSA* with different varieties of
sweet potato.

Fungus/Sweet Potato COLONY DIAMETER (mm)** Spores/ml (x106)**
Variety DAY 3 Day 5 Day 7 Day 7


Fusarium monilifbrme
Rinagaygay 37.3 63.3 88.2 6.43
UPLB Acc. 225 37.5 63.3 88.3 7.61
Kinabakab 36.5 60.8 85.3 5.61
VISCA Acc. 98 36.7 60.7 84.8 3.97

Volvariella volvacea
Rinagaygay 78.0 plates overgrown
UPLB Acc. 225 65.7 90.0 plates overgrown
Kinabakab 81.2 plates overgrown
VISCA Acc. 98 75.5 plates overgrown

Rhizopus nigricans
Rinagaygay 34.0 56.0 76.3 4.72
UPLB Acc. 225 41.8 67.7 87.6 5.53
Kinabakab 33.8 53.8 73.7 4.64
VISCA Acc. 98 32.2 50.5 69.3 1.71


*SPSA is composed of sweet potato (different varieties), brown sugar, agar bar, tap water
allowed to settle for 24 hours.


**Average of 3 replicates.


Jan. & June 1982









Philippine Phytopathology


Table 6. Comparative prices1 of ingredients in PDA and SPSA media.


PDA SPSA Price
Ingredients Price Ingredients Price Ratio2


White potato P12.00/kg Sweet potato P3.00/kg 4.0

Dextrose 31.00/kg Sucrose
(table sugar) 4.00/kg 7.85

Agar (powdered, Agar bar
Japanese brand) 300.00/kg (gulaman) 170.00/kg 1.8

Distilled water highly rain or tap much cheaper than
expensive water distilled water

1Prices as of December, 1981.
2Price of ingredient in PDA divided by price of corresponding substitute ingredient in SPSA.


Vol. 18









/Sorghum grain molds


Fig. 1. Comparative mycelial growth of Colletotrichum gloeosporioides in SPSA and PDA.


Fig. 2. Comparative growth of Stemphylium lycopersici in SPSA and PDA.


Jan. & June 1982









Philippine Phytopathology


Fig. 3. Comparative mycelial growth otfRhizopus nigricans in SPSA and PDA.


Fig. 4. Comparative growth of Aspergillus flavus in SPSA and PDA.


Vol. 18









Philipp. Phytopathol. 18: 89-101


COMPARATIVE STUDIES ON THE DIPLODIA-LIKE
ORGANISMS ISOLATED FROM FRUITS

TRICITA H. QUIMIO and YOLANDA DELA CRUZ

Associate Professor and former undergraduate student, respectively. Department
of Plant Pathology, UPLB, College, Laguna.

ABSTRACT

Pathogenicity studies showed that representative isolates of Diplodia, Botryo-
diplodia and Lasiodiplodia from a vareity of Philippine fruits were capable of cross-
infecting different fruits. Identical rots were produced by the organisms on all the
fruits tested.
When subjected to different media, temperature and light conditions, the
isolates showed variability on mycelial growth and color, stromata and pycnidial for-
mation and sporulation. Potato dextrose agar best supported the mycelial growth of
the isolates. All isolates grew and sporulated well under continuous light and at 30 C,
except isolates 4, 5, 8, and 12 which failed to sporulate under any of these conditions.
Pycnidial morphology was found to vary with the environmental conditions and
substrates thus making it unreliable for purposes of classification. Pycnidiospore
characters were more or less constant regardless of the cultural conditions. The pycni-
diospores produced by the isolates were dark and two-celled at maturity, placing them
in the genus Lasiodiplodia, following the most current taxonomy on Deuteromycetes.
Spore size, shape and ornamentation were slightly variable depending on the isolates
but they all fit into the ubiguitous species, L. theobromae. Isolates from chico, ram-
butan and santol are being reported for the first time.


In the course of a survey of fungal
diseases of Philippine fruits in 1979-81,
the senior author isolated many Diplodia-
like organisms; majority were causing rot-
ting of a variety of tropical fruits. Quite
frequently, but not always, the rot
started near the base of the fruit where
the pedicel was detached (Fig. 1). The
affected portion appeared brown at first
and grew darker and softened as it
enlarged, until dense white mycelial
growth covered the affected area. In
other cases, rots started from wounded
areas suggesting that the causal pathogens
are weak parasites causing considerable
damage especially during storage and
transit.
Diplodia, Botryodiplodia and Lasio-
diplodia constitute the majority of the
rot-producing organisms, all forming the


characteristic 2-celled, dark-colored, oval
conidia produced inside pycnidia. These
three genera were previously distinguish-
ed by the way their pycnidia are borne.
Diplodia forms scattered pycnidia,
Botryodiplodia forms pycnidia which are
clustered botryosee) within a stroma,
while Lasiodiplodia forms pycnidia
enclosed in a hemispherical stroma. De-
finitely, these characters are of little taxo-
nomic importance because of their unsta-
bility and their natural range of variation.
As a result, confusion has arisen in the
naming of these organisms and in most
cases two or three different names refer
actually to only one.
In a series of papers, Webster et al.
(1969, 1971a, 1971b, and 1974) have
shown the variability of some 250 isolates
representing several reported genera all









Philippine Phytopathology


Fig. 1. Typical fruit rots caused by Diplodia-like
c) mango, d) pineapple, e) jackfruit, f) banana.


exhibiting the Diplodia-like characteris-
tics. He proposed that the fungi pro-
ducing dark, two-celled spores in a
pyenidium be included in the genus
Diplodia thereby putting all the other
related genera as synonyms.
Following the latest concept on the
taxonomy of the Deuteromycetes, Sutton
(1980) retained Diplodia in the Sub-order
Blastopycnidianae and recognized only
one species of the genus, D. mutila. Lasio-
diplodia adopted the genus name Botryo-
diplodia and is retained in Suborder Blas-
tostromatineae, forming spores within
uni- or multilocular stromata. This
follows the earlier suggestion of Zambet-
takis (1955) that B. theobromae be re-
tained in Lasiodiplodia.
The present paper compares the
pathogenicity and cultural characteristics


organisms. a) guava, b) grapes,


of the isolates of Diplodia-like fungi
attacking a variety of Philippine fruits.
The study also aims to clarify the
relationship between the isolates and to
confirm congeneric characters and identi-
fication.

MATERIALS AND METHODS
The isolates listed on Table 1 were
used in this study. All were isolated from
diseased specimens using tissue culture
technique on potato dextrose agar (PDA).
They were maintained in agar tubes
of the same culture medium during the
course of the study. Whenever spores
were needed, the culture plates or tubes
were incubated under continuous light.

Pathogenicity Studies
All the isolates studied were in-


Vol. 18










Diplodia-like organisms from fruits


Table 1. List of Diplodia and Diplodia-like isolates and their respective fruit hosts
used in the study.

HOST REPORTED REFERENCE
ISOLATE CAUSAL
NO. ORGANISM


1 Banana
(Musa sapientum Linn.)

2 Chico
(Achras sapota Linn.)

3 Avocado
(Persea americana Mill.)

4. Mabolo
(Diospyros discolor Willd.)

5 Atis
(Annona squamosa Linn.)

6 Papaya
(Carica papaya Linn.)


7 Guava
(Psidium guajava Linn.)

8 Lanzones
(Lansium domesticum Jack.)

9 Rambutan
(Nephelium lappaceum)

10 Mango
(Mangifera indica Linn.)


B. theobromae


Wardlaw,
1931


No report


D. natalensis
B. theobromae


Home, 1926
Wardlaw, 1934


No report


L. theobromae


B. theobromae

L. theobromae

B. theobromae


Bureau of Agr.
Phil., 1926

Hunter et al.,
1969
Reinking, 1918

Srivastava &
Tandon,1969


No repui


No report


D. natalensis
B. theobromae
L. theobromae


Mallamaire, 1936
Fernando, 1937
Charles, 1906


11 Santol
(Sandoricum koetjape
[-Burm. t] Merr.)

12 Citrus
(Citrus nobilis Lour.)


No report


B. iheo, n

D. natalensis


Wardlaw & Leonard
1937
Reichert &
Hellinfer, 1932


I~------


Jan. & June 1982









Philippine Phytopathology


oculated on the following available
fruits: banana, chico, avocado, papaya,
guava, mango and citrus. These are also
original hosts of most of the isolates used.
The fruit surface was first swabbed with
sterile water, pin-pricked, then inocula-
ted with a mycelial disc placed on the
pricked areas. The inoculated fruits were
incubated inside plastic bags at 300C
until the symptoms of the disease
appeared. Uninoculated healthy fruits
served as control.


Cultural Studies

Effect of various agar media
The different isolates were culti-
vated on the following media: v-8 juice
agar, Czapeck's agar and PDA. The com-
position of the media were followed from
Tuite (1969). Twenty ml of each of the
sterile media were plated. A mycelial disc
of each of the isolates cut with a sterile
cork borer from the margins of 2-day old
colonies on PDA were planted centrally
on each medium. Incubation was done at
300C under light for 20 days.

Effect of temperature
Mycelial discs of each isolate were
planted centrally on plated PDA and
were incubated under light for 20 days
at 10, 20, 30 and 400C.

Effect of light
Mycelial discs of each isolate were
planted centrally on plated PDA and were
exposed to different light conditions as
follows: continuous light (CL), con-
tinuous darkness (CD), and alternate light
and dark (ALD). To provide for con-
tinuous darkness, plates were wrapped
with carbon paper. ALD was 12-hr dark
and 12-hr light. Incubation was done at
300C for 20 days.


In all of the above experiments,
photographs of the culture plates and
photomicrographs of the pycnidiospores
were taken after the incubation period.
Replicate plates were provided for the
study of pycnidial morphology and
pycnidiospore characters. Observations
on the following characters were noted:
mycelial growth and pigmentation;,
stromata, pycnidia formation; pycnidial
characters like shape, distribution of
pycnidia, orientation of the pycnidia with
respect to the substrate, and presence of
hairs; and pycnidiospore characters like
size, shape and ornamentation. The spore
size (length x width) was measured
using a calibrated Filar micrometer.


RESULTS AND DISCUSSION

Pathogenicity Studies
Table 2 shows that all the isolates
cross-infected their respective original
hosts with varying degrees of virulence.
Papaya and citrus appeared to be less
susceptible to the various isolates while
the guava and lanzones isolates showed
less virulence in all the inoculated host
fruits. The nature of the rots produced
were all identical.
Although the above results would
appear that all the isolates are the same
species or kind, host alone should not be
used as basis for identification. The
subsequent cultural characteristics of the
different isolates should therefore, add
light to their probable identity and no-
menclature.

Cultural Studies

Mycelial growth on culture media
The 3 media tested all supported
good mycelial growth of the 12 isolates.
The growth characteristics slightly varied


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Diplodia-like organisms from fruits


Table 2. Summary results on the pathogenecity of Diplodia and Diplodia-like isolates on
different hosts.

ISOLATE NO. DEGREE OF INFECTION
AND HOST

banana chico avocado papaya guava mango citrus
1. banana ++ ++ ++ ++ ++ ++ +

2. chico ++ ++ ++ + ++ ++ +

3. avocado ++ ++ ++ + ++ ++ +

4. mabolo ++ ++ ++ + ++ ++ +
5. atis ++ ++ ++ + ++ ++ +

6. papaya ++ ++ ++ + ++ ++ +
7. guava + + + + ++ + +

8. lanzones + + + + + + +

9. rambutan ++ ++ ++ + ++ ++ +

10. mango ++ ++ ++ + ++ ++ +
11. santol ++ ++ ++ + ++ ++ +

12. citrus ++ ++ ++ + ++ ++ +


aTaken 5 days after inoculation
++ = Fully infected (3-5 cm da rot)
+ = Slightly infected (1-2 cm da rot)


among isolates as well as according to the
medium. In general, Czapeck's medium
appeared to best support mycelial growth
than PDA and v-8 juice medium. The
pigmentation of the colonies ranged from
light olive gray to pale and deep gray to
dark olivaceous grey.

Reproductive structures on culture media
Formation of stromata and pycni-
dia was observed as early as seven days
after transfer of mycelial disc. Great
variation on pycnidial characters was


observed among isolates and among
media (Table 3). While some of the iso-
lates produced pycnidia depending on the
medium, isolates 4, 5, and 8 did not form
any on any of the media. Generally, the
pycnidia observed singly (not in groups)
were black, carbonaceous, globose and
ostiolate. Pycnidia aggregated in colum-
nar stromata were irregular shapes and
sizes. Many were also black and carbo-
naceous.
Extrusion of pycnidiospores
through the ostioles were observed 15-20


Jan. & June 1982










Philippine Phytopathology


Table 3. Pycnidial characters of isolates of Diplodia and Diplodia-like fungi on different
media incubated at 300C with continuous light for 20 days.

MEDIUM
ISOLATE V-8 juice Czapeck's Potato dextrose
agar agar agar

Loc St H Sh Loc St H Sh Loc St H Sh

1 SM GN H Su SM N H Su

2 SM N H Su M GN NH Su

3 SM GN NH GI

4

5 -

6 SM GN NH GI

7 M N H GI

8- -- --

9 SM N H Su S G H GI S GN G GI

10 SM B H GI S N G GI M N H GI

11 SM GN G GI S GNH GI S G NH I

12 SM N H GI SM N H Su



aLoc = Location
S, M, Sm superficial, submerged, superficial and submerged, respectively

St = Status
G, N, GN grouped, not grouped, grouped and not grouped, respectively

H = Hair
H, NH hairy, not hairy, respectively

Sh = shape
Su, GI, Gl, I subglobose, globose, globose and irregular, irregular, respectively


pycnidia not formed


Vol. 18









Diplodia-like organisms from fruits


Table 4. Pycnidiospore characters of isolates of Diplodia and Diplodia-like fungi on
different media incubated at 300 with continuous light for 20 days.

MEDIUM
ISOLATE V-8 juice Czapeck's Potato dextrose
NO. agar agar agar

Or SN ConC Sh Or SNCon C Sh Or SNCon C Sh

1 SG 1 +.-B O = = = = S 1 +.-D OE

2 SG 1 D OE Sm D O G 1 D O

3 = = = = = = = = = = S 1 D O




6 = = = = = = = SmG 1 D E

7 = = = = = = S 1 D

8 = = = = = = = = = =

9 Sm 1 B O Sm 1 +.- B O S 1 D E

10. = = = = = = = G 1 D O

11 G 1 +.-D O = = = = = Sm 1 D O

12 = = = = = =


aOr = ornamentation
S, G, SG, Sm, SmG striated; granular, striated and granular, smooth, smooth
and granular, respectively
SN = septa number
Con = constriction
+.-; present and absent; absent, respectively
C = color
B, D brown, dark, respectively
Sh = shape
E, OE, O ellipsoidal, oval to ellipsoidal, oval, respectively
= pycnidiospores not formed


Jan. & June 1982







Philippine Phytopathology


Pa F 6


Fig. 2. Photomicrographs showing representative spores produced on PDA by the
isolates from a) banana (#1), b) chico (42), c) avocado (43), d) papaya (44),
e) guava (47), f) rambutan (#9), g) mango (#10), and h) santol (#11), (800X).
Numbers in parentheses correspond to the isolates enumerated in table 2.


I:


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Diplodia-like organisms from fruits


Table 5. Spore dimension (L x W) of isolates of Diplodia and Diplodia-like fungi grown on
PDA at 300C with continuous light for 20 days.

ISOLATE NO. RANGE (u) AVERAGE

1 22.5-33.3 x 13.5-16.2 26.7 x 14.6
2 21.6-24.3 x 13.5-14.4 22.1 x 13.8
3 23.4-27.9 x 13.5-15.3 25.2 x 14.2
4 -
5

6 18.0-26.1 x 11.7-14.4 21.6x 13.1
7 17.1-19.8 x 10.8-12.6 18.4 x 11.7
8
9 18.0-23.4 x 11.7-13.5 20.7 x 11.1
10 18.9-27.9 x 13.5-15.3 23.2 x 14.6
11 21.6-27.0 x 11.7-13.5 24.8 x 12.8
12


days after mycelial disc transfer. They
appeared as black exudate at the mouth
of the pycnidium.
Table 4 summarizes the pycnidios-
pore characters of the isolates. PDA best
supported the production of pycnidios-
pores. Eight out of 12 isolates fruited on
PDA while only four and two fruited on
v-8 and Czapeck's, respectively. The
pycnidia of isolate 12 on PDA did not
develop pycnidiospores.
The spores produced were generally
one-celled (non-septate) and hyaline
when young and two-celled (uniseptate)
and dark when mature. Spore ornamen-
tation slightly varied among the isolates
on PDA.
Spores were commonly oval and
rarely ellipsoid. Spore sizes (L x W) of
the isolates produced on PDA are shown
on Table 5. Photomicrographs of repre-


resentative spores produced by the
isolates on PDA are shown in Fig. 2.

Effect of temperature on vegetative
growth
Generally, the 12 isolates grew best
at 300C, then at 20 C. The plates in-
cubated at 30 C were covered with
mycelium two days after mycelial disc
transfer while those at 20 C were covered
five days later. Scanty mycelial growth
was observed at 10 C and 40 C. Most of
the isolates at these temperatures did not
cover the 9 cm diam petri dish within 20
days.
The range of pigmentation of the
isolates varied from light to olive gray,
pale olive gray to dark olive gray to 10 C
to deep olive gray, deep grayish olive,
mouse gray and olivaceous black at 20
C and 30 C to pale gray, light gray at 40


Jan. & June 1982









Philippine Phytopathology


C. The color of the media exposed to
40 C changed from clear to pink.
All isolates did not produce
stromata and pycnidia at 10 C and 40 C
(Table 6). Stromata were abundant on
the isolates exposed to 30 C. They
appeared about a week after mycelial
disc transfer as cylindrical structures one
or more cm long arising from the mat of
vegetative mycelium. Stromata were
scantily developed and sometimes absent
in isolates exposed at 20 C.
The isolates exposed to 30 C pro-
duced numerous pycnidia than at 20 C
except isolate 9 which produced relative-


ly more pycnidia at 20 C. Only six out of
nine isolates which produced pycnidia at
30 C produced pycnidia at 20 C.
Pycnidial character, pycnidiospore,
size and shape and septation were not
affected by temperature.

Effect of light on growth and
reproduction
The isolates grew equally well
under all light conditions continuous
light, continuous darkness and alternate
light and darkness. Color of colonies
ranged from dark olive and olivaceous
black to the usual shades of gray.


Table 6. Effect of temperature on pycnidial production of the different isolates of Diplodia
and Diplodia-like fungi grown under continuous light for 20 days.

TEMPERATURE
ISOLATE NO. 10 20 30 40

1 + ++

2 + ++

3 ++

4
5

6 ++
7 -++

8

9 -++ +

10 ++

11 + ++
12 + ++


no pycnidia formed
2-5 pycnidia per plate
6-20 pycnidia per plate


Vol. 18




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