Official Organ of the Philippine Phytopathological Society, Inc.
PHILIPPINE PHYTOPATHOLOGICAL SOCIETY, INC.
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EDITORIAL BOARD 1992-1993
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EPIDEMIOLOGY AND CONTI
CAUSED BY PHYTOPHTF
Jocelyn P. Pedrosc
ISupported by the Southeast Asian Regional
(SEARCA), College 4031, Laguna. Part of the
School, University of the Philippines at Los Baiio!
2Respectively, former graduate student, UP
Zamboanga City, and Assistant Professor, Departi
Key words: Epidemiology, control, black str
The study was conducted in tei
Agricultural Corporation in Basilan, U
Basilan, Carbonell Farm in North Cotab
Glorriane Farm in North Cotabato, Mar
Gallardo Farm in Davao del Sur, San
Rubber Corporation in Zamboanga del
Rubber Plantation in North Cotabato)
development of black stripe. Incidence of
at Menzi Agricultural Corporation farm
plantations had the highest percentage inc
was observed at Zamboanga Rubber Cor
severity at 16.0%. Severity increased me
However, the rate of infection was slow.
period exerted minimal effects on the dev
at 0.63 g a.i./l, captafol (Difolatan) a
(Sandofan) at 0.45 g a.i./l, effectively co
at weekly intervals. The fungicides did
dryness of trees.
Rubber is one commodity with very higl
foreign exchange potential. With its diversified
use, millions of hectares of rubber are needed ti
satisfy world market demands.
The world population of rubber i
concentrated in Asia, particularly in Malaysia
Thailand, Indonesia, Philippines. and Sri Lanka. Ii
OL OF RUBBER BLACK STRIPE
'ORA PALMIVORA BUTLER1
and A. D. Raymundo2
Center for Graduate Study and Research in Agricultu
senior author's MS thesis submitted to the Gradua
(UPLB), College, Laguna.
.B now with the Western Mindanao State Universit
ient of Plant Pathology, UPLB, College, Laguna
pe, rubber, Phytophthora palmivora.
rubber plantations in Mindanao (Menzi
diversity of the Philippines Land Grant in
Lto, Philtread (Firestone) in North Cotabato,
F rm in Mcrtl
to determine the occurrence, severity, and
black stripe was high in all plantations except
Zamboanga Rubber Corporation and USM
idence of 100%. Highest severity of infection
oration at 90.0% while Menzi had the lowest
nths during the period of June to September.
Temperature and relative humidity during the
elopment of black stripe. Metalaxyl (Ridomil)
: 2.34 g a.i./l, and oxadixyl + mancozeb
ntrolled black stripe when spraying was done
not affect latex production or caused panel
the Philippines, rubber is a very profitable agr<
industry. Presently, a total land area of 59,086 1
h is planted to rubber in Mindanao mostly i
I Zamboanga del Sur, Basilan, and North Cotabat
Rubber production in the Philippines is lo'
s despite an ideal climate for the crop. One of th
Problems causing great reduction in yield is th
Occurrence of pests and diseases. Numerous
diseases which directly or indirectly affect yield (
ave been reported. Of these diseases, black stripe c
f the tapping panel, caused by Phytophthora e
almivora Butler, is reported to cause considerable
)sses in production (Liyanage et al., 1977). Severe
lack stripe infection causes uneven bark renewal I
resulting in burns and depressions in the panel thus
making subsequent tapping impossible.
Few studies on the epidemiological aspects of I
lack stripe are available. Knowledge on the (
development, incidence, distribution, and severity c
f the disease will enable rubber planters to e
)rmulate strategies to reduce infection to d
manageable levels. r
The increasing incidence and severity of the 4
disease have necessitated a search for effective p
ingicides that can be used to control black stripe s
1 plantations. This paper reports on the incidence, c
severity, development, and control of black stripe a
i selected plantations in Mindanao. r
MATERIALS AND METHODS
Incidence and Severity of Black Stripe. A
survey was conducted in ten plantations in the
rovinces of Zamboanga del Sur, Basilan, Davao
el Sur, and North Cotabato to determine the
occurrence, incidence, and severity of black stripe.
assessment was done during the rainy months of
une and July, a period favoring germination of
pores and resulting in severe infection. Tappable
ibber trees of the same age were considered in the c
A map of each plantation was used to locate
areas where high incidence of black stripe was F
previously reported. These areas were marked and
one-hectare area was considered the site for
disease assessment. The method used by Soyza et
1. (1983) was modified and adopted to accurately F
ssess the disease. The one-hectare area was
ivided into 16 quadrats with each quadrat
measuring 25m x 25m and enclosing from 30 to 45
rees. Each quadrat was subdivided into 4 grids.
ihe intersection of the grid or the centerpoint was F
signed a serial number which was randomly
obtained by drawing lots. Panels exhibiting typical
symptoms of black stripe were counted and a
1984) shown below. A completely randomized
design with 6 replications was followed in this
developmentt of Black Stripe
A one-hectare rubber plantation at the
University of Southern Mindanao, Kabacan, North
Cotabato was used to study the temporal
development of black stripe. The method by Soyza
;t al. (1983) was, likewise, followed in assessing
disease severity. All trees in 6 quadrats selected
andomly within the area with each enclosing 30 to
[5 trees, were marked and tagged as sampling
points. Following the above rating scale, disease
everity assessment was done monthly for a period
if three months. Relative humidity, temperature,
nd rainfall data were obtained and possible
relationships with severity were analyzed. The
parentt infection rate was estimated by using the
ogistic model of Vander Plank (1963).
Disease Index Description
0 No infection
1 1-25 % of the bark affected
2 26-50 % of the bark affected
3 51-75% of the bark affected
4 76-100% of the bark affected
Percentages of infection and severity were
omputed by using the following equations:
no. of infected tapped trees
percentt Incidence =---------------------------x 100
total no. of tapped trees in the area
sum of all disease ratings
percentt Severity =----------------- x 100
total number of ratings x
maximum disease scale
fieldd Test of Fungicides
rmpp. rmyuMop u. 1iw, Vea. e: i-a
the Firestone Plantation in Makilala, North plantations (Table 2). The lowest disease
Cotabato planted to RRIM 600 clone and where the of 16.0% was recorded at the Menzi Agr
trees are from 6 to 10 years old. A factorial Corporation plantation followed by 22
experiment involving fungicidal treatments and 2 Carbonell, 24.6% at UPLG, 25.8% at Fi
application intervals, once a week and once every 2 27.2% at USM, 31.6% at Clorriane, 5:
weeks, in randomized complete block design with Sandique, 55.2% at Martinez, and 62
3 replications and 10 plants per treatment, was Gallardo Farm. The most severe infec
followed. The fungicides were applied with a 5 cm 90.9% was observed at the Zamboanga
paint brush on the tapping panel. Assessment of Corporation plantation. Differences in
disease severity was done twice, at 4 weeks and at conditions most likely influenced the varia
8 weeks after fungicidal application. Percent severity of black stripe in the plantations. I
disease control was computed as the difference et al. (1977) has reported that this varial
between mean percentage severities of control and also be the effect of spacing, topography
treated trees in a plot and divided by the percentage and population density.
severity of control trees. The existence of more virulent strain
plantations with higher disease severities ca
discounted. Phytophthora isolates from rubl
RESULTS AND DISCUSSION been observed to be variable in many cl
(Turner, 1961). Pathogenic strains of Phytc
Incidence and Severity of Black Stripe have been identified in experiments condt
Phytophthora leaf fall (Planters Bulletin, 19
Generally high incidence of black stripe was Disease severity before tapping
observed in all plantations during the rainy months significantly higher than after tapping.
of June and July (Table 1). USM and Zamboanga Firestone rubber plantation, severity before
Rubber Corporation plantations had the highest was 70.3 % as compared to 25.8% after
incidence of 100%. Sandique, Gallardo, and (Table 3). Panels before tapping appeared
Martinez had high incidences of 99.2, 99.0, and and were heavily infected. It appears 1
98.1%, respectively. These were followed by removal of the latex affected the availal
Glorriane with 89.1 %, Philtread with 86.0%, and inoculum for subsequent infection.
Carbonell and UPLG both with 80.4%. Menzi
Philipp. Phytopathol. 1992, Vol. 28:1-8
Table 1. Incidence of black stripe on rubber at different locations in Mindanao from June to
Plantation Location Date Incidencel
University of the
Univ. of Southern
Bansalan, Davao del sur
Zamboanga del Sur
I Obtained in a 1 ha. area per plantation
I aIUi l. Z CVOIlLy UI UIo..1~i uu I I IUUi I U Il& yrIulallulla 111 piAxuralau 1 ull .ul. .
Menzi Agricultural Corporation 16.0
Carbonell Farm 22.0
UP Land Grant 24.6
Philtread (Firestone) 25.8
USM Rubber Plantation 27.2
Glorriane Farm 31.6
Sandique Farm 53.5
Martinez Rubber Corporation 55.2
Gallardo Farm 62.7
Zamboanga Rubber Corporation 90.9
I Mean of 6 replications with 30-45 trees per replication.
LSD (.05) : 15.1
CV (%) :31.9
Firestone Rubber Plantation, Makilala, Noi
ime of Disease
Mean of 6 replications with 30-45 trees per replication.
SD (.05) : 14.6
V(%) : 23.6
able 4. Efficacy of different fungicides in control
days after application.
Jntreated) Every 2 weeks
Every 2 weeks
'aptafol 4F Weekly
Every 2 weeks
Ixadixyl + Weekly
mancozeb Every 2 weeks
Each figure is a mean of 3 replications.
LSD (.05) : Fungicides
CV (%) : Frequency of application
ling black stripe on rubber at 30 and 60
After 30 Days After 60 Days
Field Test of Fungicides
Metalaxyl, captafol 4F, and oxadixyl
mancozeb were highly effective in controlli
black stripe (Table 4). The application
fungicides significantly reduced the severity
black stripe at the rates used. Weekly spraying M
more effective than one spray every two weel
This comparison was significant 30 days af
application and became very pronounced at 60 da
after application. The lowest disease severity
4.2% was observed in oxadixyl + manco2
weekly treatment. This was not significant
different from the percentages of severity obtain
with metalaxyl and captafol 4F weekly applicatic
which wer 60 7 and R 3 resnectivelv. The
preventing the emergence of strains of
palmivora that are tolerant to the compounds. ?k
+ only would the pathogen encounter two kinds
ig barrier, it would also have to contend with t,
Af modes of action considering the differing acti
Af ingredients of the compounds. It would also
is possible to use the three fungicidal treatments
s. this study in alternate applications as they ha
iMARC. 1984. Economics of production and VANDER PLANK, J. E. 1963. Plant Diseases:
marketing of rubber among small holders in Epidemics and Control. Acad. Pres. New
the Philippines. USMARC Monitor 5:11. York. 349 pp.
IOYZA, DE A. G., CHANDRA YEAH, C. S. and A. M. TAN. 1979. A new
SAMARANAYAKE, V. ABEY MARDENE, formulation for controlling black stripe. Proc.
A. H. R. JAYARATNE and S. WILBERI. RRIM Planters Conf. Rubber Res. Inst.
1983. A survey on the incidence and pattern Malaysia, p.400-408
of distribution of the brown bast disease of
Hevea in Sri Lanka. J. Rubber Res. Inst., Sri
Lanka 61: 1-6.
'URNER, P. D. 1961. Variation of Phytophthora
palmivora Butler from Theobromae cacao
isolates from West Africa. Trans. Br. Mycol.
Soc. 44: 409-416.
CERCOSPORA ARACHIDICOLA A
AND ITS RELATIONSHIP TO
Rodolfo A. Paningbal
Part of the Ph.D. thesis of the senior author
Bafios, Laguna, Philippines.
1Associate Professor, Department of Plant Prote
2Associate Professor, Department of Plant Path
College, Laguna, Philippines.
Partial resistance of five peanut cult
Hori causing early leafspots and Phaeoisn
causing late leafspots were analyzed. Ag.
350680 and NC 76446(292) sustained s
latent period (LP50), earlier to reach 5-rm
sporulation capacity and efficiency than
Across cultivars, C. arachidicola exhib
shorter latent period (LP50), 7-day shor
standard 5-mm lesions, eightfold less sl
in sporulation than did P. personata. Inf
differ significantly across cultivars. Des]
and efficiency, development of both dis
End-of-season disease intensity, area und
50% level of disease severity better
Vanderplank's apparent rate of infection.
reduced infection efficiency and sporulal
levels of severity of early leafspot in the I
LP50, infection efficiency and sporulatior
reduced late leafspots in the field. Infecti
related to severity of both diseases in the I
ND PHAEOISARIOPSIS PERSONATA
DISEASEE PROGRESS IN PEANUT
n1 and Oscar S. Opina2
submitted to the University of the Philippines at Lo
tion, Visayas State College of Agriculture, Baybay
rlogy, University of the Philippines at Los Baiios
vars to infection by Cercospora arachidicola
riopsis personata (Berk. and Curt.) von Arx
inst both pathogens, cultivars PI 259747, PI
gnificantly longer incubation period, longer
2 lesions, lower infection efficiency and less
susceptible cultivars BPI P9 and UPL Pn4.
ted 4-day shorter incubation period, 6-day
er infectious period, 13-day earlier to reach
Drulation capacity and fourfold less efficient
actionn efficiencies of both pathogens did not
ite great differences in sporulation capacity
ases in the field did not significantly vary.
:r disease progress curve, and time to reach
described disease development than the
Prolonged incubation and latent periods and
on efficiency were correlated with reduced
eld whereas reductions in incubation period,
capacity and efficiency were correlated with
)us period and lesion growth rates were not
destructive diseases (Garren and Jackson, 1973
Allen. 19831. Combined infection bv boti
n reduce pod yield by an average of 57 kg ha-1
r each percent defoliation (Backman and
rawford, 1984). C
Management of peanut leafspots has been
primarily by multiple application of fungicidal
rays (Smith and Littrell, 1980). With the high a
)st of fungicides and the development of h
mgicide-resistant strains of the two pathogens, the is
iltivation of peanut resistant varieties becomes (I
creasingly important. Moreno (1985) reports d
at chemical control of plant diseases is seldomly n
practiced by most tropical farmers. d
Complete resistance to early and late leafspot d
mgi has not been found among various species of n
rachis (Subrahmanyan et al., 1985). Resistance sl
iaracters are associated with prolonged incubation o
ad latent periods, smaller lesion size, reduced so
iorulation per lesion, delayed defoliation and o
duced infection frequency (Aulakh et al., 1972; 2
assan and Beaute, 1977; Nevill, 1981; p
mingbatan and Ilag, 1984; Ricker et al., 1985; so
ibrahamanyan et al., 1985; Sowell et al., 1976;
reen and Wynne, 1986; Paningbatan, 1987). F
analysis of cohort life table statistics showed that P
distance traits of peanut cultivars to either
ithogen were also expressed as significant
ductions in germinated conidia/total conidia ratio 2
sions/total conidia ratio or infection efficiency, d
aximum relative growth rate and net reproductive P
te (Paningbatan and Opina, 1990). Resistant t
iltivars significantly prolonged the mean w
neration time of both pathogens (Paningbatan F
d Opina, 1990). w
Despite this good number of studies, a d
rmparative analysis of partial resistance of peanut p
livars to both pathogens has not been done. h
ius, the study was conducted to analyze and rn
impare the components of partial resistance of p
anut genotypes to both pathogens and to fo
termine the relationship between each component tt
resistance and certain parameter of disease p
ogress of early and late leafspots. ir
MATERIALS AND METHODS
collection, Isolation and Maintenance of Isolates
Leaves of peanut infected by C. arachidicola
id P. personata were collected and brought to the
boratory for isolation into pure culture. The
olation technique described by Paningbatan
980) was followed. Infected leaves were surface-
sinfected with 0.5 % sodium hypochlorite for 2-3
minutes, rinsed in sterile distilled water, blotted
-y with sterile filter papers and incubated for 1-2
iys in moist chamber. Conidia picked up with
oistened sterile needle with the aid of
ereomicroscope were aseptically streaked on
lion agar slants. Cultures were maintained by
really streaking conidial suspension to fresh
lion agar slants monthly and incubating them at
5-300C. Three-week old onion agar cultures of P.
'rsonata and C. arachidicola grown at 270C
;rved as source of inoculum (Paningbatan, 1980).
reparation of Inoculum and Inoculation to Test
Peanut cultivars BPI P9, UPL Pn4, PI
259747, PI 350680 and EC 76446(292) with
fferent levels of resistance to C. arachidicola and
personata were used in this study. The first
/o are commercial cultivars in the Philippines
while the other three originated from Peru,
onduras and Uganda, respectively. Three plants
ere grown in 20-cm clay pots with heat-
sinfested soil in the screenhouse with six
)ts/variety. The ambient temperature and relative
nmidity ranged from 25-32 and 60-98%,
spectively. Crop cultural recommendations
opposed by PCARRD (1978) were routinely
allowed except for fungicide application to control
e leafspots. The fourth and fifth leaves of each
ant's main stem were tagged and uniformly
oculated late in the afternoon by spraying with an
atomizer the inoculum suspension of each fung
adjusted to 25,000 conidia ml-1 of sterile distill
water Conidial viability at the time of inoculati
ranged from 99-100%. Tween 80 was added at 1
of inoculum suspension. Inoculated plants we
covered with moistened plastic bags for 48 hours.
Measurement of Components of Partial
The components of partial resistance of cro
to pathogens that are used to compare cultiva
such as incubation period and reproductive capaci
per lesion and efficiency per unit lesion area we
examined. Unless specified, the F-test and t-te
were used to analyze variances and compa
treatment means, respectively, based on a split-pl
in a randomized complete block design with s
replicates. The degree of association of t]
components with the disease progress in the fie
determined using coefficient of correlation.
Incubation period. The study on incubati(
period was conducted six times. The number
days after inoculation was recorded when abo
half square millimeter initial lesions had appeared
The macroclimatic air temperature and relati
humidity ranged from 21-330C and 74-98M
respectively. The incubation periods of bo
pathogens on the five peanut cultivars due to eai
of the pathogens ranged from 109-151. TI
number of lesions that started sporulating at certa
period of time were inspected by probit analyst
(Shaner, 1980) to determine the LPI and LP5
LP1 was used to predict the onset of sporulati(
when 1 % of lesions are sporulating while LP,
when 50% of them are already sporulatin
Arbitrarily, LP1 was used to predict the onset
sporulation of a population of lesions due to tl
species of the pathogen and the peanut cultivars.
Infectious period. This was estimated fro
10 random lesions, one lesion per leaflet, whi(
were observed daily. Since all the lesions caust
by either pathogen kept on producing conidia whi
still intact, for practical purposes, the period
leaflet abscission was considered as the "end"
us Lesion growth. In examining the lesic
ed growth rates of the pathogens, leaflets with 4
on lesions each were tagged. At 3-day intervals fro
% 18 to 33 days after inoculation, lesion area w
;re estimated using a clear transparent grid. Oi
replication consisted of an average of four leaftle
with one lesion considered per leaflet. Pooled da
from three trials were used in the analysis durii
which the relative humidity and temperature rangi
from 70-98% and 21-350C, respectively. T1
ps slopes derived from simple linear regressi(
irs analysis of natural logarithm of lesion areas again
ty time and the predicted length of time to reach
:re standard lesion size were used to compare relati,
est colonization rates of the pathogens as influenced I
.re the peanut cultivars.
ot Infection efficiency. This parameter w
;ix quantified by getting the ratio of lesions th
he formed to the number of conidia inoculated p
Id cm2 of leaf area. Then number of conid
deposited on the leaf was observed a day aft
on inoculation. One square centimeter of random le
of samples were cut and placed in a fixing-clearii
ut solution (ethanol-acetic acid at 20-30%) for at lea
d. 24 hours. Ten random samples per plant p
ve variety were considered. After fixing and clearin
%, the sample tissues were transferred to 0.01% ac
th fuchsin in lactophenol for three minutes, mount
ch on microscope slides and conidia were county
he with a microscope.
in Reproductive capacity and efficiency. TI
;is reproductive capacity of lesions was calculated
0. the gross conidial production until lesions hl
on detached as a result of defoliation. T1
50 reproductive efficiency of each pathogen w
g. calculated based on the mean number of conid
of produced per day per unit lesion area. The lesi(
ne areas observed within five days starting from tl
onset of sporulation and the corresponding dai
m conidial yields were used for calculation. Ti
ch randomly chosen leafspots for each pathogen at oi
ed leafspot per leaf were marked for conidi
le production using an improvised spore collect,
of attached to a vacuum pump operating at 3-5 ps
of the pressure range previously determined mo
effective in collecting the conidia of bo
llnogtll. O.iUU1C iCj W"t *XMW - w__w -.,
00 hours daily until the infected leaflets had m(
tached from the plant. res
sease Progress of Early and Late Leafspot inm
i Different Peanut Cultivars int
Field experimental design. A field th(
periment was carried out during the dry season at we
e location in the Central Experiment Station of ar
SUniversity of the Philippines at Los Bafios, inc
iguna, Philippines. It involved the same five ste
anut cultivars with different levels of resistance se<
P. personata and C. arachidicola planted to a ph
3 hectare sandy loam field. The seeds were we
illed in the field furrows spaced at 75 cm at the tra
te of 96 kg ha-1 (approximately 15 plants meter- in
in plots of 2 x 6 meters. The experiment was rai
plicated three times based on a split-plot in a as:
ndomized complete block design. Except for of
ercospora leafspot control, all cultural so
commendations were followed (PCARRD, wt
'78). Complete fertilizer (14-14-14) was applied fr(
[ring sowing and at six weeks after. Tridemorph
rand Name: Calixin 50 EC) was sprayed at the 01
te of 0.8 ml commercial formulation per 16 liters w,
water at 2-week intervals to prevent peanuts co
)m being infected by Puccinia arachidis pli
ubrahamanyam et al., 1985). Likewise, ra
anocrotophos (Azodrin 168) at three ml TI
mmercial product per liter was sprayed at 14-day pl
tervals, whenever necessary. Following its w;
commended dosage, azinphos-ethyl (Gusathion pl
) was sprayed alternately with monocrotophos.
ring rainy periods, an adjuvant Tenac was b)
ixed to the spray solution at the recommended le;
sage of 0.1 ml Tenac per ml of pesticide cc
.mmercial formulation. fo
In the field experiment on disease progress of pe
rly and late leafspot, four rows of IPB Var I corn le;
-re sown three weeks ahead of planting the test
ants, and two meters away around each peanut to
ot (4 x 6 meters) to minimize interplot ur
terference. Plots of 2 x 8 were planted across fo
ain blocks to check on the natural and cross
fection occurence of leafspot in the field. Mean
monthly macroclimatic relative humidity and
mperature ranged from 78-86% and 26-290C, w
spectively, during the course of the experiment, at
nth ranged from 76-287 mm and 15-25 days,
Primarily inoculum preparation and
iculation. The primary inoculum for transfer
o the field was produced on BPI P9, a
;ceptible variety, grown in 20-cm clay plots in
screenhouse. At one month old, the seedlings
re inoculated with the virulent isolate of C.
ichidicola and P. personata. The aqueous
culum was adjusted to 25,000 conidia ml" -of
rile distilled water and was atomized onto
dlings. The seedlings were incubated inside a
stic chamber for two days after which, they
re transferred to the screenhouse. At the time of
nsfer into the field, i.e. three weeks after
>culation, the number of sporulating leafspots
iged from 80-100 per pot. The pots, randomly
signedd to the plots, were positioned in the center
each plot. Positioning of primary inoculum
irces was done late in the afternoon, and plants
re watered daily for three weeks to keep them
Gathering and analysis of data.
Pservation on percent leaf area infected per plant
.s initiated two weeks after inoculation and
ntinued at 1-week intervals thereafter. Five
Lnts in the inner two rows of each plot were
idomly selected prior to each assessment data.
e rating on an individual plant basis for each
int was pooled and averaged, and the final value
is used in calculating the disease severity of
mnts per plot.
Percent diseased leaflets was also computed
assessing the number of leaflets containing at
ist one lesion in a randomly selected plant and by
hunting the missing leaflets. Each plant had the
allowing information: total leaflets = nodes x 4;
recent defoliation (Yi) = [(leaflets lost) + total
flets] x 100.
Shaner and Finney's (1977) method was used
calculate disease severity in terms of the area
der the disease progress curve (AUDPC) as
AUDPC = [ (Yi + + Yi) 2 1 (Xi + i Xi)
lere Yi = percent diseased or defoliated leaflets
th. Wth nhcprvatinn and Y. timp nf thpe ith
Philipp. Phytopathol. 1992, Vol. 28: 9-2"
in AUDPC's were examined by using analysis of LP50, the pathogen took 18.4-26.6 days, with BP:
variance and comparison of means. P9 sustaining the shortest LP50 and PI 35068(
Field data was transformed to linearity by the showing the longest period.
logit transformation, In [Yi + (100 Yi)] Averaged across cultivars, C. arachidicoh
(Vandeqplank, 1963). Apparent rates of disease initially sporulated six days earlier thai
increase were estimated from the slopes obtained P. personata. Compared with observed onset, tho
by regressing transformed data against time. predicted LPI underestimated the onset o
Correlation coefficients were used to examine sporulation by 3.4 and 5.4 days respectively fo
the degree of association of the components C. arachidicola and P. personata. LP50 o
severities (Fn), AUDPC's, apparent infection rates C. arachidicola and P. Personata were calculated
and the predicted number of weeks to reach 50% as 15.7 and 22.2 days, respectively, across:
level of disease severity (T50) (Steel and Torrie, cultivars.
1980). Infection period. Infectious period o
C. arachidicola ranged from 3.7-7.4 days where:
that of P. personata ranged from 9.2-14.7 (Table
RESULTS 1). Both pathogens showed shorter infectiou:
period on susceptible cultivars than on resistan
Components of Partial Resistance to ones. Comparative, lesions of C. arachidicoh
C. arachidicola and P. personata remained infectious seven days shorter than P
personata regardless of cultivars.
Incubation period. Across the peanut Lesion growth. Table 2 presents thi
cultivars, C. arachidicola produced lesions 3.7 comparative colonization rates of the tw<
days earlier than P. personata (Table 1). Against pathogens on the different peanut cultivars. C
either pathogen, the ranking of the five cultivars arachidicola produced biggest lesions on BPI P
was the same with BPI P9 and UPL Pn4 exhibiting but smallest on PI 259747 and EC 76446(292
relatively shorter incubation periods than PI which was reduced by three times in size. Lesion:
259747, PI 35t' 0,( and Ec 76446(292). Under the of P. personata on PI 259747, PI 3500680 and E(
conditions of the experiment, C. arachidicola 76446(292) were likewise significantly smaller ii
infectious period of C. arachidicola (Ca) and P.
different peanut cultivars.l
LATENT PERIOD (LP)
rved Predicted3 INFECTIOUS
set4 LPI LPso PERIOD
7.7 12.9 4.4 c
) 7.5 13.7 3.7 e
9.1 16.8 5.1 e
t 9.9 18.2 4.7 e
t 9.4 16.7 5.4 d
1.6 8.7 15.7 5.1
6 12.4 18.4 9.2 c
6 12.0 19.1 11.9 b
13.8 24.0 12.0 b
12.9 26.6 13.0 ab
13.2 22.9 14.7 a
8.8 12.8 22.2 12.36
% level by DMRT.
mIn July, 1987 to February, 1988.
g upon the cultiva s. that showed sporulation onset over time. LPI
period when 50% is sporulauting. r ranged from 90-97% and were all
fiction by C. arachidicola (Ca) and P. personata
nt levels of resistance. I
:)CULATION VARIETY PATHOGEN
27 30 33 MEAN MEAN
11.55 15.30 24.00 11.71 a
9.42 12.03 20.23 9.46 b
3.88 4.57 5.12 3.83 d
7.43 10.18 13.52 7.16 c
4.20 4.87 6.33 4.06 d
7.30 c 9.39 b 11.84 a 7.24 a
4.77 5.92 6.98 4.30 d
2.97 3.65 5.30 2.78 e
1.08 1.55 1.83 1.10 f
1.37 1.70 2.48 1.28 f
1.35 1.50 2.12 1.27 f
2.31 h 2.86 gh 3.74 f 2.14b
personata (Pp) days after inoculation to d
PATHOGEN CULTIVAR INCUBATION Obsei
Ca BPI P9 7.7 d 8
UPL Pn4 8.2 d 10
PI 259747 10.3 c 12
Pi 350680 10.5 c 14
EC 76446(292) 10.2 c 14
Mean 9.4 11
Pp BPI P9 10.5 c 16
UPL Pn4 11.8 b 16
PI259747 14.3 a 22
PI350680 14.6 a 22
Ec 76446(292) 14.7 18
Mean 13.1 18
1 In a column, means with the same letter are not significant different at 5
2 Means were from pooled data of six replicates each of six trials done fro
3 Based on probit analysis of a total 109-151 Ca and Pp lesions, depending
indicates the day when 1% of lesions is sporulating whereas LP50 is the
4 At least two lesions were sporulating.
Table 2. Enlargement of lesions (mm2) due to in
(Pp) on five peanut cultivars with differ
HOST DAYS AFTER IN(
PATHOGEN CULTIVAR 18 21 24
Ca BPI P9 4.8 6.90 8.15
UPL Pn4 3.50 4.65 6.92
PI 259747 2.00 3.23 3.37
PI 350680 3.27 3.88 4.65
EC 76446(292) 2.12 3.17 3.65
Mean 3.21 fg 4.37 e 5.35 d
Pp BPI P9 1.80 2.73 3.58
UPL Pn4 1.20 1.60 1.97
PI 259747 0.60 0.72 0.83
PI 350680 0.57 0.70 0.85
EC 76446 (292) 0.62 0.87 1.15
Mean 0.96 j 1.32 ij 1.68 i
Table 3. Comparative lesion growth, infection efficiency and conidial productivity of lesions due to
infection by C. arachidicola (Ca) and P. personata (Pp) on peanut cultivars with different
levels of resistance .
LESION GROWTH (nmil2) REPRODUCTIVITY
PATHOGEN CULTIVAR INFECTION OF LESIONS
Ratel Predicted Delay in EFFICIENCY
Days to Days Capacity3 Efficiency
after Relative conidiaa/ conidiaa/
51nni2 to BPII P9 lesion) mm2)
Ca BPI P9 0.107 ab 19.0 0.18 a 1,954 c 305 c
UPL Pn4 0.116 a 21.6 2.6 0.12 c 1,023 cd 256 c
PI 259747 0.056 d 31.7 12.7 0.06 d 216 d 56 e
PI 350680 0.100 ab 23.2 4.7 0.08 d 530 d 135 d
EC 76556 (292) 0.066 ed 29.5 10.7 0.07 d 865 d 120 de
Mean 0.089 25.0 7.7 0.10 918 175
Pp BPI P9 0.089 b 28.3 0.20 a 19,289 a 1,551 a
UPL Pn4 0.098 b 32.8 4.5 0.15 b 11,088 b 1,090 b
PI 259747 0.078 c 46.1 17.8 0.08 d 580 d 122 de
PI 350680 0.100 ab 40.5 12.2 0.11 c 1,156 cd 89 c
EC 76446(292) 0.076 c 44.6 16.3 0.08 d 2,980 c 327 c
Mean 0.088 38.5 12.7 0.12 7,163 676
In a column, means with the same letter are not significantly different at 5% level by DMRT.
2 Estimated by simple linear regression of lesion areas transformed to natural logarithm against time. Correlation coefficients are all highly
3 Includes cumulative daily conidial yield until removal of lesion by defoliation.
I1.::.,.1 Il.... ,.anhln l 11O0? V-I 1Q. U-11
Fhilipp. Phytopathol. 1992, Vol. 28: 9-23
Infection efficiency. The infection efficiency
of the two pathogens on each peanut cultivar
differed, with susceptible cultivar sustaining
significantly higher values than with resistant
cultivars (Table 3). For instance, 0.08 infection
efficiency by. C. arachidicola was obtained in BPI
P9 whereas 0.06 was obtained on PI 259747 -
indicating a threefold reduction due to the
resistance of the latter. As against C.
arachidicola, the ranking of peanut cultivars based
on infection efficiency of P. personata was
perfectly the same with BPI P9 (0.20) giving the
highest and PI 259747 (0.08) and Ec 764486 (292)
(0.08) the lowest.
Reproductive capacity and efficiency. Two
characters of sporulation of lesions were examined:
the capacity and efficiency (Table 3). The data
show that suspectible cultivar BPI P9 supported
more conidial yield for both pathogens per lesion
than resistant ones. Comparatively, the mean
conidial reproductive capacity of C. arachidicola
across cultivars (918 conidia lesion-1). Moreover,
C. arachidicola was fourfold less efficient to
produce conidia per square millimeter of lesions
than P. personata was.
Disease Progress of Early and Late
Leafspots in the Field
Disease progress curves. Figure 1
summarizes the untransformed disease progress
curves of C. arachidicola and P. personata on the
five peanut cultivars based on three measures of
disease severity. For each measure of disease
severity, four parameters were observed or
computed; the final disease severity (Fn); the area
under disease progress curve (AUDPC); the
Vanderplankian rate of disease progress curve r;
and Ihe predicted time to reach 50% level of
disease severity, (T50) (Table 4).
Based on percent leaf area infected per plant
(Fig. 1); early leafspots initially appeared two
weeks after field-placement of primary inoculum
sources in BPI P9 but three weeks after on PI
259747 and PI 350680. On the other hand, late
leafspots initially appeared on BPI P9 at three
weeks after but on PI 259747, PI 350680 and EC
76446(292) it appeared four weeks after.
Comparatively, early leafspots appeared 1-2
weeks ahead of late leafspots in the field depending
upon the cultivar. Defoliation started from 3-4
weeks and 3-6 weeks after placement, respectively.
The end-of-season disease severities were
significantly higher on BPI P9 than on PI 259747,
PI 350860 and EC 76446(292) (Table 4).
Examination of the various parameters of each
disease severity measures indicates that Fn,
AUDPC and T50 showed generally similar ranking
of the peanut cultivars against the two pathogens.
Vanderplankian r did not give ranking of the
cultivars consistent with other parameters
particularly when the disease severity was based on
percent defoliation per plant. The ranking of
cultivars against P. personata was less distinct than
the ranking of cultivars against C. arachidicola
based on r values but was more distinct when based
on T50 (Table 4).
Comparatively, differences in mean values of
Fn, AUDPC, r and T50 means between pathogens
were not significantly different for all measures of
the disease severity across cultivars.
Relationship between disease severity and
cohort life and reproductivity statistics and
components of partial resistance. Correlation
coefficients were used in relating the components
of partial resistance to disease severity parameters
in the field. For C. arachidicola, prolonged
incubation periods were correlated (P=0.01) with
reduced Fn, AUDPC and r and with increased T50
(Table 5). Prolonged observed and estimated latent
periods (Lpl and LP50) were correlated with
reduced Fn (P=0.01), ACDPC (P=0.05) and with
increased T50 (P=0.05). Infection periods and
lesion growth rates were not correlated with any of
the disease severity parameters due to
C. arachidicola. Sporulation capacity was only
positively correlated (P=0.05) with AUDPC but
reductions in sporulation efficiency were
consistently correlated (P=0.05) with increased
T50 and decreased Fn, AUDPC and r.
Incubation period of P. personata was less
consistently correlated with disease severity than
that of C. arachidicola. Prolonged incubation
periods of P. personata were correlated (P=0.01)
with reduced Fn and with increased T50 (P=0.01).
Reductions in LP50 were correlated (P=0.05) with
increased Fn, and AUDPC and with decreased
Philipp. Phytopathol. 1992, Vol. 28: 9-23
C. arachidicola P. personata
Weeks after placement of primary inoculum sources
Fig. 1 Disease progress of C. arachidicola and P. personata based on three different measures of
disease severity as affected by peanut cultivar resistance.
Philipp. Phytopathol. 1992, Vol. 28: 9-23
Table 4. The final disease severity (Fn), area under the disease progress curve (AUDPC), rate of
disease increase (r) and the predicted time to reach 50% disease level (T5o) due to C.
arachidicola (Ca) and P. personata (Pp) as influenced by peanut cultivar resistance.
Fn AUDPC r T50
Ca BPI P9
EC 76446 (292)
Pp BPI P9
EC 76446 (292)
,a BPI P9
EC 76446 (292)
EC 76446 (292)
EC 76446 (292)
Leaf Area Infected/Plant
82.80 ab 429 a
78.80 b 285 b
36.67 c 104 c
35.67 cd 106 c
34.33 cd 92 cd
90.37 abc 600 a
93.00 ab 671 a
88.10 abcd 478 b
86.93 bed 476 b
81.17 cde 433 b
88.63 a 491 a
73.20 a 292 b
53.90 b 150 c
50.53 be 155 c
43.37 bc 117 cd
1 Values are means of 3 replicates. In a column, means within each disease severity parameter with the same letter are not significantly different at
5% level by DMRT.
2rvaUes in units wk"1 were estimated by simple linear regression of logits in [Yi ;(100 Yi)] of percent disease severity against time. Severity
values after 90 days and 112 days from sowing respectively for BPI P9 and UPL Pn4, and for the other three cultivars were excluded in
analysis. Fn is in percent whereas TS0 is in weeks.
0 730 bed
rihnpp. riytepatnol. IYYv, vol. AD: Y-A3
leaf area infected per plant due to C. ara,
Incubation Period -.987 **
Latent Period, Observed -.932 **
LPI -.960 **
LP50 -.973 **
Lesions: Size .833 *
Growth Rate .769 ns
Days to Reach 5 mm2 .799 ns
Infection Efficiency .906 *
Infectious Period -.649 ns
Sporulation Capacity .799 ns
Sporulation Efficiency .941 *
SFn indicates final disease severity; AUDPC as area under the
rate of infection; and T50 as the predicted time to reach 50%
Philipp. Phytopathol. 1992, Vol. 28: 9-23
However, infection efficiency and prolonged
periods to reach a standard five mm2 lesion were
correlated (P=0.01) with decreased Fn and
AUDPC and with increased T50. Increases in
sporulation capacity and efficiency were highly
correlated (P=0.01) with increased Fn and
AUDPC and with shortened T50.
Results of the analysis of components of
partial resistance of peanut cultivars to early
leafspot and late leafspot pathogens confirmed
earlier reports (Sowell et al., 1976; Hassan and
Beaute, 1977; Nevill, 1981; Paningbatan and Ilag,
1984; Ricker et al, 1985; Subrahmanyam et al.,
1985; Green and Wynne, 1986) that partial
resistance of peanut to both pathogens was
expressed as prolonged incubation period,
prolonged latent period, prolonged infectious
period, reduced sporulation capacity and reduced
lesion size. The infection efficiency and
sporulation efficiency per unit lesion area are two
parameters included in this study which were found
to be consistently better descriptors of the effect of
resistance than gross conidial production
particularly for C. arachidicola. Infectious period
and lesion growth rates were not correlated with
disease severity of both early and late leafspots and
therefore not good parameters to quantify partial
On the basis of the components to partial
resistance which were validated in the- field, PI
259747, PI 350680 and EC 76446(292) could be
potentially valuable parental lines for early and late
leafspot breeding program. Results of recent
works on resistance of these genotypes to
C. arachidicola (Nevill, 1981) and to P. personata
(Paningbatan and Ilag, 1984; Subrahmanyan et al.,
1985) corroborate this observation.
When disease occurs, its increase may be a
critical factor in influencing crop losses by
leafspots and this should be considered in
-rr *.....1 ... ... x. .. -
correlated more highly with some of the
components of resistance than did apparent
infection rates of early and late leafspots. Since it
reflects the onset of disease in the field and timing
of disease increases between rating intervals over
the entire season, AUDPC might estimate better
the disease progress than the r calculated by
regression analysis. As it integrates the estimated
period of disease onset based on the regression line
equation, T50 better describes disease progress as
influenced by peanut resistance that delays and
retards disease epidemic than r does. Thus, in
evaluation for resistance r might conceal cultivars
that should have been identified as significantly
resistant based on the period to reach 50% level of
disease or T50.
Percent leaf area infected, leaflets infected
and defoliation per plant as bases for disease
severity could be used in analyzing disease
progress of both leafspots. Although positive
correlations were found between defoliation and
severity due to early leafspots (Green and Wynne,
1986; Johnson et al., 1986) or to late leafspots
(Paningbatan and llag, 1984), caution must be
taken because defoliation may be due to natural leaf
abscission caused by large area of the upper canopy
of the cultivar (Watson et al., 1986).
The higher correlations obtained between
parameters of disease severity and components of
partial resistance to C. arachidicola such as
incubation period, LP1, LP50, infection efficiency
and sporulation efficiency per unit lesion area
indicate the importance of these in assessment of
resistance. For P. personata, the higher
correlation obtained with LP50 make these
statistics better descriptors of late leafspot severity
than LP1 and observed latent period. LP50,
infection efficiency, predicted period to attain 5-
mm2 lesion, sporulation capacity and sporulation
efficiency per unit lesion area exhibited higher
correlations with disease severity and hence are
important parameters in assessment of late leafspot
disease progress. Lesion growth rates and
infectious period were not related to early and late
leafsnot severity in the field. Thus, these
parameters ot resistance did not have significant
influence on epidemic development of early and
Despite the great differences in sporulation
capacity and efficiency between the two pathogens
across cultivars, both diseases attained severities
which were not significantly different from each
other. The inferior conidial reproduction of C.
arachidicola might have compensated by its 6-day
shorter latent period. In epidemic development,
conidia produced relatively early in the season
must have had greater impact on disease
development than when produced later in the
season (Parlevliet, 1979; Vanderplank, 1984).
Thus, prolonging latent period and limiting
conidial reproduction of the pathogens would be
more desirable traits and should be emphasized in a
peanut breeding program. Prolonging the latent
rnmupp. rnytopatnoi. iyy1 vol. ra: -zL3
rmuupp. rnylopaumM. I~y, vol. Ja: Y-5j
ALLEN, D.J. 1983. Pathology of tropical NEVILL, D.J. 1981. Components of resistance to
legumes. Wiley, New York, USA 488 p. Cercospora arachidicola and Cercosporidium
personatum in groundnuts. Ann. Appl. Biol.
AULAKH, K.H., R.S. SANDHU and M.S. 99:77-86.
SAUNAS. 1972. Resistance to "tikka"
leafspot in groundnut germplasm. Indian J. PANINGBATAN, R.A. 1980. Culture,
Agr. Sci. 42: 952-955. morphology and pathogenic variation of
Cercospora species causing leafspots in
BACKMAN,.P.A. and M.H. CRAWFORD. 1984. peanut (Arachis hypogaea L.). M.S. Thesis.
Relationship between yield loss and severity University of the Philippines at Los Bafios,
of early and late leafspot diseases of peanut. College, Laguna. The Philippines. 116 p.
Phytopathology 74: 1101-1103.
PANINGBATAN, R.A. 1987. Host influences of
GARREN, K.H. and C.R. JACKSON. 1973. epidemic development of leafspot caused by
Peanut diseases. Pages 429-494. In Peanuts: Cercosporidium personatum (Berk. and
Culture and Uses. Amer. Peanut Res. Educ. Curt.) Deighton in peanut. Ann. Trop. Res.
Assoc., Inc. Okla. State Univ., Oklahoma 9:24-23.
PANINGBATAN, R.A. and LINA L. ILAG 1981.
GIBBONS, R.W. 1980. Peanut improvement Two leafspots of peanut in the Philippines:
research technology for semiarid tropics. etiology and host response to infection. Phil.
T1r2 __ 11 '7 '73 F.. ">-_ T- _- ----- I / -. __. .
-lJp. .i vi.. 11.01. J.,IcU a I U I IIJI.
(ICRISAT), Patancheru, A.P. India.
GREEN, C.C. and J.C. WYNNE. 1986. Field
and greenhouse evaluation of the components
of partial resistance to early leafspot in
peanut. Euphytica 35: 561-573.
HASSAN, R.M. and M.K. BEAUTE, 1977.
Evaluation of resistance to Cercospora leaf
spot in peanut germplasm potentially useful in
a breeding program. Peanut Sci. 4:78-83.
JOHNSON, C.S., M.K. BEAUTE and M.D.
RICKER. 1986. Relationship between
components of resistance and disease progress
of early leafspot on Virginia-type peanut.
MORENO, R.A. 1985. Plant pathology in the
small farm context. Ann. Rev. Phytopathol.
i-tiiniuDnl ot iN, A.t. ana LIINA L. 'IL-A.
1984. Resistance of peanut cultivars to
Cercosporidium personatum (Berk. and Curt.)
Deighton. Phil. Agr. 67:17-24.
PANINGBATAN, R.A. and O.S. OPINA. 1990.
Comparative cohort life and reproductivity
table analysis of Cercospora arachidicola
Hori and Phaeosaripsis personata (Berk. and
Curt.) von Arx on peanut. Trans. Nat. Acad.
Sci. Technol, Philipp. 22:347-372.
PARLEVLIET, J.E. 1979. Components of
resistance that reduce the rate of epidemic
development. Ann. Rey. Phytopathol.
PCARRD (Philippine Council for Agriculture and
Resources Research and Development).
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peanut. Los Bafios, Laguna. The
Philippines. 54 p.
RICKER, M.D., M.K. BEAUTE and C.L.
CAMPBELL. 1985. Components of
resistance in peanut to Cercospora
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SHANER, G. and R.E. FINNEY. 1977. The
effect of nitrogen fertilization on the
expression of slow-mildewing resistance on
Knox wheat. Phytopathology 67:1051-1056.
SMITH, D.H. and R.H. LITTRELL. 1980.
Management of peanut foliar diseases with
fungicides. Plant Dis. 64:356-361.
SOWELL, G., D.H. SMITH and R.O.
HAMMONS. 1976. Resistance of peanut
plant introductions to Cercospora
arachidicola. Plant Dis. Rept. 60:494-498.
STEEL, R.G.D. and J.H. TORRIE. 1980.
Principles and procedures of statistics: a
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New York, USA. 633 p.
SUBRAHMANYAM, P., J.P. MOSS, D.
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V.R. RAO. 1985. Resistance to leafspot
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~n n ~~
Philinn. Phvtonathol. 1992. Vol. 28: 24-33
YIELD OF TARO [COLOCASL)
AS AFFECTED BY TARO FI
INOCULATED AT VARI(
R.M. Gapasin, Ci
and A. I
Respectively, Professor, Department of Plant ]
Research Assistant, Root Crop Research and Train
Agriculture (ViSCA), Baybay, Leyte 6521, Philippinm
The effect of taro feathery mosaic virus
taro plants was determined using mechan
infected with the disease. In both pot and I
of taro (variety, Kalpao) from 2.80 to 58.1
Inoculation of plants at the earlier stage of
incidence and yield reduction than inoculalt
infected with TFMV produced more suckers
Taro [Colocasia esculenta (.L.) Schott], a
member of the Aracea Family, is an important
staple food crop of the indigenous societies of the
tropicall world. Throughout the islands of the
Pacific, Asian archipelago, Central Africa, West
[ndies and the islands of the Caribbean and Central
America, taro forms an important part of the
people's diet (de la Pefia, 1970; Plucknett, 1970).
[n the Philippines, taro is .important either as
luman food, animal feed or raw material for a
variety of processed products (Villanueva and
Despite the extensive use and importance of
aro in the tropical world, few comprehensive
studies of the maladies affecting the crop have been
undertaken. Along with leaf blight and storage
diseases, taro feathery mosaic is a serious disease
Af taro at present (Palomar et al., 1983). The
disease symptom is either an indistinct interveinal
:hlorosis and vein-banding or a pronounced white
Feather mosaic nattern with or without mottling of
ESCULENTA (L.) SCHOTT]
ATHERY MOSAIC VIRUS
)US GROWTH STAGES
isanta E. Sajise
protection (DPP), Assistant Professor and Science
ng Center (PRCRTC), Visayas State College of
(TFMV) infection on yield and growth of
cally inoculated and seedpieces already
eld experiments TFMV reduced the yield
4% and 20.24 to 32.14%, respectively.
growth, generally showed higher disease
on at the later stage. In addition, plants
han uninfected ones.
he leaves. Symptoms, regardless of severity,
disappear gradually as the leaves mature. In severe
:ases, infected plants become stunted with
nalformed leaves The taro feathery mosaic virus
TFMV) can be transmitted by a vector,
rarophagus proserpina Kirk. or by mechanical
neans through wounds and farm implements
Taro like cassava and other root crops can be
propagated colonally. Suckers, tubers or corms are
ised to establish new plantings. This method
however, ensures perpetuation of systematically
nfecting pathogens like TFMV and can be a
primary means by which the virus may be
introduced into new areas (Kaiser et al., 1982)
vhich if left unchecked may cause the disease to
each epedemic proportions with resultant
iuhstantial e-onnmic losm1t
iilipp. Phytopathol. 1992, Vol. 28: 24-33 25
are stands of clover reduced yield by 48.4% in desired seedpieces requirement to be used as test
reenhouse tests and 54.3% in field tests They plants for pot and field experiments was met.
irther stated that yield loss due to infection by Land preparation, Experimental Design and
Ifalfa mosaic virus (AMV) and bean yellow Lay-out
mosaic virus (BYMV) in both greenhouse and field
:sts ranged from 23.55% to 100%. In Africa, Pot Experiment. An area of 10m2 was
.aiser and Loiue (1982) reported losses in yield prepared, manually-cleaned of debris and levelled.
ue to cassava mosaic virus (CMV) to range from Healthy seedpieces were planted individually in a
0.90% to 100%. 14-inch diameter clay pots filled with sterilized
In British Solomon Islands, a lethal form of soil. The pots were arranged in randomized
irus known as Alomae was reported by Gollifer complete block design (RCBD) with eight
1976) to attack taro plants which could result to treatments replicated ten times. Each pot
)tal failure of the crop. On the other, hand in the represented a replication. The treatments were
'hilippines, Palomar et al. (1983) revealed that a designated as follows: TO uninoculated control;
iosaic-like disease of taro known as taro feathery TI -inoculation at the first month after planting;
mosaic was observed in Kalpao and Takudo T2 inoculation at the second month after planting;
varieties in ViSCA, Leyte and Eastern Samar, T3 inoculation at the third month after planting;
respectively. Though their study covered a broad T4 inoculation at the fourth month after planting;
ange of information about the disease such as T5 inoculation at the fifth month after planting;
disease incidence, symptomatology, transmission T6 inoculation at the sixth month after planting;
nd host range, no further attempt was made on the T7 naturally infected seed pieces.
Oilipp. Phytopathol. 1992, Vol. 28:24-33
Figure 1. Disease free (A) and severely infected (
exhibited by the diseased plant.
Inoculation. Gabi plants were inoculated
monthly from the first to the sixth month after
planting. The time of inoculation was set at early
morning or late afternoon. Before inoculation,
certain amount of Celite was added and mixed to
the liquid inoculum. Inoculation was done by
gently rubbing the cotton balls previously dipped
in the inoculum, on the upper surface of the leaf.
Then, a stream of tap water was poured on the
leaves to remove the excess hCelite.
Fertilization, Pest Control, Cultivation
The plants were applied with complete
fertilizer (14-14-14) during planting and one month
after. Insect pests were controlled alternately by
spraying Malathion and Parapest while blight
disease was controlled using Dithane M-45
following the manufacturer's recommended rates.
Snravino was done one month after nlanting and
B) taro plants. Note the feathery mosaic symptom
The crop was harvested 8 month after
planting. The corms were cut from the vegetative
,arts, cleaned and weighed, while the
suckers/runners were counted.
The following data were gathered:
1. Disease incidence on mother plants and
2. Number of suckers/runners produced by
the mother plants
3. Weight of corms
RESULTS AND DISCUSSION
Inoculation Times 1 2 3 4
(control 0 0 0 0
T1 1st month 0 4 9/4 10/7
T2 2nd month 0 0 6 6/7
T3 3rd month 0 0 0 7/3
T4 4th month 0 0 0 0
T5 5th month 0 0 0 0
T6 6th month 0 0 0 0
T7 Already infected
with TFMV 10 10/6 10/6 10/8
1 Average of 10 plants; means followed by a common letter are
... -.- -j ...... .. .....
18 Philipp. Phytopathol. 1992, Vol. 28: 24-33
disease (TI-T4, T7) than those inoculated later (T5 reported to affect symptom expression of virus
6). However, disease incidence declined at infected plants. Grasmick and Slack (1985)
maturity. Among the inoculated treatments, plants reported that potato spindle viroid (PSTV)
ioculated on the first month after planting showed concentration increased faster in tomato plants
ie highest incidence (4.88) while those inoculated grown at 31 C than at 23 C and that low light
n the sixth month gave the lowest incidence (0.50) intensity (17-18 hr) did not critically limit-iroid
f the disease. Highest incidence (8.75) was synthesis but symptoms developed more slowly and
observed in plants already infected with the were severe at high light intensities.
disease. 3. The symptom "loss" characteristic of the
This result indicates that younger plants were virus. TFMV had the tendency to lose its
lore susceptible to the disease than older ones. As symptoms in taro infected plants regardless of
-ported by Bos (1970) the age of the attacked disease severity (Palomar, 1982). Similarly,
ssue or organ is an important factor in Reinert and Gooding (1978) concluded that the
determining host reaction. In his study on red first 2 to 3 leaves to develop above the inoculated
lover mottle virus in leaves of Beka beans, a great leaves of Nicotina tabacum showed severe tobacco
umber of chlorotic local lesions was found if streak virus (TSV) symptoms, but leaves that
loculated 10 d after sowing, whereas when formed later were symptomless.
ioculated 6 d later, only numerous tiny chlorotic More suckers were produced in the inoculated
esions developed. Likewise, viruses multiply treatments and plants already infected than in
lost ranidlv in vounger plants or in voune uninoculated ones. Significant differences were
Tj 1st month
T2 2nd month
T3 3rd month
T4 4th month
T5 5th month
T6 6th month
T7 Already infected
Average of 10 plants; means followed by a
ommon letter are not significantly different at 5% lev
---r --------- /
Effects of TFMV on Corm Yield Field Experiments
The yield of the plants were significantly Plants already infected with TFMV show
affected by the time of TFMV inoculation As the highest disease incidence on mother plants a
shown in Table 2, yield of taro inoculated on the produced more suckers (Table 3). Among t
first month afte planting was significantly lower inoculated plants, those inoculated on the fi
than those plants inoculated at the later months, but month had the highest disease incidence wh
not significantly different from plants already plants inoculated on the sixth month had t
infected with the disease. Those inoculated from lowest. Uninoculated plants showed slig
the second to the sixth month after planting did not infections on both mother plants and suckers. TI
significantly exhibit reduced yield compared to the infection could be attributed to insects such as ta
control. Per cent yield reduction for all treatments plant hoppers that feed on the plants which a
ranged from 2.80 to 58.04. The results of the known to be vectors of TFMV (Palomar 198K
experiment are similar with the findings of The results of the field experiment showed t
Uyemoto et al. (1981) who observed that early same trend as in the pot experiment, however
virus infection (maize chlorotic mottle and maize more suckers were produced by the mother plant
dwarf mosaic viruses) significantly reduced the the field experiment which is understandable sin
yields of corn. In like manner, corn plants infected those that were grown in pots had limited space f
earlier with maize rayado fino virus (MRFV) sucker production. The results also confirm ai
significantly affected the yield of plants (Toler et strengthen findings of the pot experiment sin
al., 1985). Moreover, Ahhormanesh and Shalla younger plants were also observed to mo
(1981) reported that yield reduction of field-grown susceptible to the virus than the older plants.
tomatoes inoculated with tomato mosaic virus was
due to high virulence of the virus and to the fact Effects of TFMV on Corm Yield
that the plants were intentionally inoculated at an
early stage of growth. The yield of taro was affected by the disea
Plants exposed to TFMV infection at longer regardless of the time of inoculations (Table 4
period of time obtained the highest yield reduction Per cent yield reduction ranged from 20.24
compared to plants that became infected 3 or 6 32.14. Among the treatments that were inoculate
months after inoculation (Table 1). Plants already those that were already infected before or
infected with the disease from first month to the planting showed the highest reduction in yie
eighth month (incidence declined during the 7th while plants inoculated on the fifth month had tl
and 8th months obtained the highest per cent yield lowest. There was no significant difference
--..---.'-- C" gO ',A T *1 -- I 1 11 H I II
u.AIUVUJ CLL ULU U OLI ILIUU111U 4IlI IIIUaLUUaIIUI
resulted in higher yield reduction of 49.65 per cei
compared to those plants that succumbed to tt
disease later (T2-T6). This finding collaborate
with the observations made by Toler et al. (198!
and Ahoormanesh and Shalla (1981).
A better picture of yield loss may have bee
predicted if severity of the disease with time w-
used. Since TFMV cause systemic infection
incidence may be used with some caution to predict
yield loss assessment in the absence of other
V m01Ua4 lu mul 10IpuIncu uy Illicr anu ncver
1) (1982) that early infection (2-3 weeks afto
it transplanting) of tomato yellows or yellowing vin
e to tomato plants caused the greatest reduction <
d yields (60-83 %) but infections occurring as late t
) 5 weeks before harvest resulted in only 25% yiel
reduction. Agrios et al. (1985) also showed thi
n pepper plants inoculated with cucumber mosai
s virus in early growth stages had significantly fewer
, total and marketable fruits than in plants inoculate
t later. Fruit yield improved in almost dire
r proportion to the lateness of cucumber mosai
inoculation of the plants.
uninoculated with the virus produced the lowest
number of suckers while plants inoculated on th
first month had the highest number of sucker
produced followed slightly by plants already
infected with the disease (Table 4). Although their
was no significant effect of the disease on th
production of suckers among treatments, the result
suggest that the virus still enhanced sucke
production supporting the results obtained in th
With the latency and/or masked symptom
characteristic exhibited by TFMV disease a
discussed earlier, a study to investigate th
mechanisms involved should be encouraged
Likewise, the effect of using naturally infected
plants should be further verified before an'
conclusion could be drawn as to be drawn as to th,
effect of TFMV disease on yield of taro.
affected by different time of taro feathery mosaic virus (TFMV) inoculations taken monthly from planting up to harvest (pot experiment.)'
MONTH Number of
Total Average, Suckers
Inoculation Times 1 2 3 4 5 6 7 8
(control 0 0 0.33 1 1/3 1.7/7 1/10 1/14 6.03/34 0.73/4.25 107.00
T 1st month 0 5/1 8/13 9/21 6/31 7/45 6/47 4/65 45/223 5.62/27.88 163.67
T2 2nd month 0 0 8/10 6/17 8/28 8/48 3/56 3/38 36/207 4.50/25.88 153.33
T3 3rd month 0 0 0 4/26 9/26 9/40 6/28 6/51 34/175 4.25/21.88 133.00
T4 4th month 0 0 0 0 8/27 7/29 5/46 2/47 22/149 2.75/18.62 120.67
T5 5th month 0 0 0 0 0 5/46 7/39 4/62 16/147 2.00/18.38 136.33
T6 6th month 0 0 0 0 0 0 5/38 5/60 10/98 1.25/13.25 123.00
T7 Already infected
with TFMV 10 10/14 9/25 7/57 6/61 8/47 5/51 5/46 60/258 7.50/32.25 156.33
Philipp. Phytopathol. 1992, Vol. 28: 24-33 33
AGRIOS, G.N., M.E. WALKER and D.N. PERA, DE LA R.S. 1970. The edible aroids in
FERRO. 1985. Effects of cucumber mosaic the Asian-Pacific area. Proc. 2nd Int. Trop.
Virus inoculation at successive weekly Root and Tuber Crops. 1: 136-140.
intervals on growth and yield of pepper
(capsicum annuum) plants. Plant Disease 69: PLUCKNETT, D.L. 1970. The status and future
52-53. of the major edible aroids, Colocasia,
Xanthosoma, Alocasia, Cystosperma and
AHHORMANESH, A. and T.A. SHALLA. 1981. Amorphophallus.
Feasibility of cross-protection for control of
tomato mosaic virus in fresh market field- RAGLAND, C.K., C.L. CAMPBELL and J.W.
grown tomatoes. Plant Disease 65: 56-58. MOYER. 1986. The effects of clover yellow
vein virus and peanut stunt virus on yield and
BOS, L. 1970. Symptoms of Virus Diseases in two clones of Landino White clover.
Plants. Oxford and TBH Publishing Co., 2nd Phytopathology 79: 557-558.
Edition, New Delhi. pp. 16-19
REINERT, R.A. and G.Y. GOODING. 1987.
Philipp. Phytopathol. 1992, Vol. 28: 34-44
RESPONSE OF SHEATH BLIGHT DEVELOPMENT TO
RICE CROP MANAGEMENT IN LOWLAND AND
A.K.M. Shahjahan and T.W. Mew
Division of Plant Pathology, Bangladesh Rice Research Institute, Joydebpur, Dacca, Bangladesh
apartment of Plant Pathology, International Rice Research Institute, P.O. Box 933, Manila, Philippines
A D l'TD A IT-
Philipp. Phytopathol. 1992, Vol. 28: 34-4,
high yielding rice cultivars are responsive to high panicle initiation (PI) to early booting stage.
amounts of nitrogen, this creates conditions Inocula of Rhizoctonia solani isolate No. 44-8 were
conducive to sheath blight development (Ou, prepared by growing the fungus for 7-10 days in
1985). The disease has become one of the autoclaved rice hull:rice grain medium (3:1).
biological constraints to sustain stable crop Inoculation was done at booting stage by placing
production and to obtain higher yields in tropical 50 ml of the inocula/hill between the tillers al
environments. It is, therefore, important to assess water level (lowland) or 300 ml/row (upland). All
the cultural management of the disease to reduce plants except those in the border rows were
cost and loss. In this study, we tried to assess inoculated. The inoculated, inoculated + sprayed
sheath blight development in response to crop and check plots were designated as DL-1, DL-2,
MATERIALS AND METHODS
Layout, and cultural practices of thg
experiments. Experiments were conducted during
the 1985 and 1986 dry and wet seasons undei
lowland and upland environments in the farm o:
International Rice Research Institute. Experiment!
were laid out in split-plot design with threat
replications. The plot sizes wert
5 x 3 m and 3 x 3 m for lowland and upland
respectively. The following components at tht
specific levels were integrated: I. Variety (V) = 3
(a) IR54 or IR64, (b) IR58 and (c) IR62 (for bott
lowland and upland); II. Spacing (S) = 2
Lowland: (a) 25 x 25 cm, (b) 20 x 15 cm (line )
Hill); upland: (a) 40 cm or 30 cm, (b) 20 cn
(row); III. Nitrogen rate (N) = 2: (a) 60 k1
N/ha; (b) 120 kg N/ha; IV. Fungicide sprays wit[
triphenyltin acetate (Brestan 60 WP) was applied
to manipulate three disease levels; a) inoculation o:
plots with R. solani, b) fungicide spray ant
inoculation, c) plots with natural infection as checl
and as background disease pressure.
IR54 and IR64 are both long duration (120-
125 days) and moderately resistant cultivars; IR62
is intermediate both in duration (110-115 days) anc
in disease reaction, and IR58 is susceptible anc
early maturing (95-100 days). Planting followed
the common practice as in lowland (transplanting
of 21-day-old seedlings in hills) and in upland
(seeding at 100 kg seeds/ha in rows) conditions.
Nitrogen as urea in lowland and ammoniunr
sulphate in upland was applied in two equal splits:
at three weeks after transplanting or seeding and al
WP at 1 kg ai/ha was sprayed twice: 1 and 10 days
after inoculation to the DL-2 plots only. The
lowland field was irrigated regularly to maintain
standing water whereas the upland field was
irrigated by surface or sprinkler to keep the soil
moist and when necessary, a condition favorable
for ShB development (Watanabe and Takano,
Measurement of disease, yield, and yield
loss. Both horizontal (% tillers infected) and
vertical (lesion height/plant height) development of
sheath blight in plots with different treatment were
recorded at maturity. A sampling procedure of
partial replacement at 20% using a "W" pattern
was followed to measure the disease development.
The number of samples/plot was 10 hills or points
for (upland) and the sample unit was 5 tillers/hill
or point or a total of 50 tillers/plot. The final
disease severity (DS) was calculated by using the
Mean lesion height
of infected hills No. of tillers infected/plot
DS, x ---- xlO
mean plant eight total no. of tillrs
The number of productive and non-productive
tillers/plot were counted prior to harvesting. Rice
yield in each treatment was measured by harvesting
6 m2 (3 x 2 m) and 5.8 m2 (2.4 x 2.4) for lowland
and upland, respectively. The losses of grain yield
incurred by sheath blight were calculated using the
Yield of sprayed plots Yicid of inoculated plots
Grain yield loss () x 100
Phmipp. Phytopathol. 1992. Vol. 28: 34-44
-,-A ri QC/. 7- m---- t-i,
RESULTS of 41.5%
disease development. anearn ougni severiues or q1.3 7 anu lt.t 70, resp
development under lowland (mean disease severity (Tables 1, 2).
1.5%) was similar to that under upland (mean Grain yield loss. There was
lisease severity 41.3%). No significant differences difference in yield loss under different nitrol
n ShB development were observed in the three spacing combinations. Infection at booting
:ultivars differing in maturity when the disease critical to grain production occurred t
pressuree was high (i.e. inoculated) in both lowland inoculation, the early and late cultivars s
md upland environments (Tables 1, 2). In these similar amount of loss under both enviro
wo seasons, there were frequent rainfall and the (Tables 4, 5). It was the rate of nitrogo
temperature and humidity of the air were high spacing that influenced yield loss, In the Ic
especially during the maximum tillering to milk the mean yield losses, estimated on the b
stages. In the next season (dry '86) when the plots check and sprayed plots, were 13.9% (490
were not inoculated but with the carry over and 22.9% (870 kg/ha) at disease seve
nocula, the cultivar differences were very apparent 41.5% and 10.8%, respectively, while thosi
Table 3). The development of ShB in the control upland were 15.9% (444 kg/ha) and 23.4
Lots was very low due to low inoculum kg/ha) at disease severity of 41.3% and
sclerotiumm) level in the field soil. Brestan spray, respectively (Tables 1, 2, 4, 5).
)n the other hand, reduced the severity of ShB The yield loss was 25.9% or 970 kg/hi
significantly (Tables 1, 2, 3). There was variety kg N and 300 cm2 spacing (i.e. 20 x 15 cm
by disease-level interactions for disease lowland, but in the upland, it was 28.4%
development suggesting that the varietal difference kg/ha at 120 kg N and 40 cm row spacin,
in disease development would depend on the calculated on the basis of sprayed plots (Ti
inoculum level. 5, 6). However, differences in yield loss 1
Table 1. Sheath blight severity (DS) and yield of three rice cultivars grown under different nitrogen x spacing (NS) treatments and three disease
levels (DL), late dry season, 1985, lowland, IRRI.
DL-1b DL-2b DL-3b
(NSc) 1R54 1R58 IR62 Mean, 1R54 1R58 IR62 Mean IR54 IR58 IR62 Mean
Meana sheath blight DS (%)
NISI 34.2 be 36.9 41.3 a 37.5 c 5.7 a 11.1 a 8.4 a 8.4 a 1.0 a 0.8 a 0.0 a 0.6 a
N1S2 28.9 c 45.6 ab 40.6 a 38.3 bc 7.8 a 15.8 a 13.7 a 12.5 a 1.3 a 1.9 a 0.4 a 1.2 a
N2S1 44.7 a 44.9 ab 42.9 a 44.2 ab 5.3 a 10.6 a 10.8 a 8.9 a 0.7 a 0.6 a 0.9 a 0.7 a
N2S2 39.1 ab 52.8 a 46.1 a 46.0 a 10.3 a 17.5 a 12.9 a 13.5 a 1.6 a 1.7 a 1.4 a 1.6 a
Meana grain yield (tons/ha)
NISI 4.01 a 2.19 a 2.80 ab 3.00 4.98 a 2.78 c 3.27 b 3.68 4.42 a 2.35 b 3.32 b 3.4 "
N1S2 4.02 a 2.25 a 2.93 a 3.07 5.04 a 2.92 bc 3.91 a 3.96 4.45 a 2.40 b 3.53 a 3.5
N2S1 3.59 b 2.15 a 2.80 ab 2.85 4.95 a 3.02 b 3.41 a 3.79 4.31 a 2.51 ab 3.33 b 3.4
N2S2 3.86 a 2.20 a 2.69 b 2.92 4.59 h 3.25 a 3.82 a 3.89 4.47 a 2.66 a 3.56 a 3.6
aMeans of three replications. Means followed by a common letter in a column are not
significantly different at the 5% level by LSD.
bDL-1 = inoculated with R. solani. DL-2 = inoculated + sprayed with Brestan.
DL-3 = control.
CN1 = 60 kg/ha, N2 = 120 kg N/ha, SI = 25 x 25 cm. S2 = 20 x 15 cm spacings.
Table 2. Sheath blight disease severity (DS) and grain yields of three rice cultivars grown under different nitrogen x spacing (NS) treatments and three disease levels (DL), wet
season, 1985, upland, IRRI.
Varieties DL-la DL-2a DL-3a Mean treatmentsb DL-1 DL-2 DI-3 Mean
Meanc sheath blight DS (%)
IR54 40.3 ax 15.5 aby 13.7 ay 23.2 ab NIS1 36.9 ax 11.0 by 10.5 by 19.5 b
IR58 43.6 ax 17.4 ay 17.0 ay 26.0 a N1S2 39.0 ax 14.4 aby 12.4 by 21.9 b
IR62 39.9 ax 10.5 by 13.8 ay 21.4 b N2SI 40.9 ax 13.8 aby 16.6 aby 23.8 ab
Mean 41.3 x 14.4 y 14.8 y 23.5 N2S2 48.3 ax 18.6 ay 19.9 ay 28.9 a
Mean 41.3 x 14.4 y 14.8 y 23.5
Meanc grain yield (tons/ha)
IR52 2.19 bz 3.08 abx 2.71 by 2.66 b NIS1 2.47 az 3.34 ax 2.96 ay 3.0 a
IR58 2.31 bz 2.97 bx 2.70 by 2.66 b N1S2 2.51 az 3.11 abx 2.85 ay 2.9 a
IR62 2.57 az 3.21 ax 2.99 ay 2.92 a N2SI 2.02 bz 2.84 ex 2.62 by 2.5 b
Mean 2.36 z 3.08 x 2.80 y 2.75 N2S2 2.42 az 3.05 bcx 2.77 ay 2.8 a
Mean 2.36 z 3.08 x 2.80 y 2.8
aDL-1 = plots inoculated with R. solani, DI-2 = plots inoculated sprayed with Brestan,DI-3 = control.
bN1 = 60 kg/ha, N2 = 120 ke/ha. SI = 40 cm, cm, S2 = 20 cm spacings.
CMeans of three replications x four NS treatments (for variety)and three reps x three varieties (for NS treatments). Means followed by a common letter in a column (a,b,c) or a row (x,y,z) under varieties or
treatments are not significantly different at the 5% Level by LSD.
~r;~aull 17oV Ut)lLIIIU l~nl
IR54 17.5 bx 2.1 ay 8.4 axy
IR58 47.7 ax 5.9 ay 11.5 ay
IR62 11.0 bx 1.0 ax 1.3 ax
Mean 25.4 x 3.0 y 7.0 y
IR54 2.93 ay 3.20 ax 3.01 ax
IR58 2.86 az 3.40 ax 3.13 ay
[R62 2.04 by 2.36 bx 2.25 bx
Mean 2.61 y 2.99 x 2.80 xy
aDL-1 = plots inoculated with R. solani. DI-2 = plol,s inoculated + spn:
bNl = 60 kg N/ha, N2 = 120 kg N/ha, Sl = 30 cm, S2 = 20 cm iow
eMeans of three replications x four NS treatments (for variety) and three
treatments are not significantly different at the 5% level by ISDI)
Meanc sheath blight DS (%)
9.3 b NISI 16.1 bx
21.7 a NIS2 20.1 abx
4.4 b N2S1 37.1 ax
I1.8 N2S2 28.3 abx
Mean 25.4 x
Meanc grain yield (lon)s/ha)
3.05 a NISI 2.47 ay
3.13 a NIS2 2.53 ay
2.22 b N2S1 2.88 az
2.80 N2S2 2.55 az
Mean 2.61 y
Icd with Brestan, )1-I = control
icps x three varictics (lor NS Ireatmenns). Means followed by a common I
Table 4. Loss of grain yield by three rice cultivars due to sheath blight at different nitrogen x spacing (NS) treatments, late dry season, 1985, lowland, IRRI.
Meana grain yield loss
Treatments Estimated on the basis of control plots Estimated on the basis of sprayed plots
(NS)b IR54 IR58 IR62 Mean IR54 IR58 IR62 Mean
NISI 9.3 a 6.8 b 15.5 b 10.5 b 19.5 b 21.1 c 14.4 b 18.3
N1S2 9.6 a 5.5 b 16.9 b 10.8 b 20.2 b 23.0 c 25.1 a 22.8
N2S1 16.7 a 14.4 a 15.9 b 15.7 a 27.4 a 28.9 ab 17.9 b 24.7
N2S2 13.6 a 17.5 a 24.4 a 18.5 a 15.8 b 32.3 a 29.5 a 25.9
Mean 12.3 11.2 18.2 13.9 20.7 26.3 21.7 22.9
Actual loss (kg/ha)
NISI 410 b 160 b 520 b 360 c 970 b 590 b 470 b 680
N1S2 430 bn 150 b 600 b 390 bc 102 Ob 670 b 980 a 890
N2S1 720 a 360 ab 530 b 540 ab 360 a 870 ab 610 b 950
N2S2 610 ab 470 a 870 a 650 a 730 b 1060 a 113 0a 970
Mean 540 290 630 490 1020 800 800 870
a Means of three replications. Means followed by a common letter in a column are not significantly different at the 5% level by LSD. To compare 2 varieties means at each treatment,
LSD .05 (percent loss) = 7.1% and 7.6%; (amount of loss) = 230 kg/ha and 320 kg/ha for DL3-DL1 and D.L2-DL1, respectively.
b DL-1 = plots inoculated with R. solani, DL-2 = plots inoculated + sprayed with Brestan, DL-3 = control.
c N1 = 60 kg N/ha, N2 = 120 kg N/ha, Sl = 25 x 25 cm and S2 = 20 x 15 cm spacings.
(NS)b IR54 IR58 IR62 Mean IR54
NIS1 16.5 ab 20.6 a 13.0 a 16.7 a 26.9 ab
N1S2 15.5 b 12.2 a 8.2 a 11.8 a 22.1 b
N2S1 30.2 a 16.1 a 20.1 a 22.1 a 39.1 a
N2S2 15.8 ab 9.4 a 12.6 a 12.6 a 27.1 ab
Mean 19.4 14.6 13.5 15.8 28.8
NISI 509 ab 534 a 433 ab 492 a 910 a
NIS2 444 b 329 a 231 b 335 a 717a
N2S1 771 a 412 a 616 a 600 a 1146 a
N2S2 370 b 281 a 394 ab 349 a 793 a
Mean 523 389 418 444 891
a Means of three replications. Means followed by a common letter in a column are not significantly different at the 5% level by LSI
13.9% and 16.5%; (amount of loss) = 618 kg/ha and 591 kg/ha for DL3-DLI and DL2-DII, respectively.
b D1l = plots inoculated with R. solani, DL2 = plots inoculated + sprayed with Brestan, DL-3 = control. CNI = 60 kg N/ha, SI
(NS) IR54 IR
N1S2 -3.1 a 9.Ua U.1 b .U a 3.2 a 1I.!
N2S1 6.5 a 3.8 a 17.7 a 9.3 a 12.9 a 14.(
N2S2 1.4 a 14.4 a 11.2 ab 9.0 a 9.1 22.
Mean 2.1 8.5 8.9 6.5 8.1 15.:
Actual loss (kg/ha)
NISI 106 a 208 ab 150 ab 155 a 148 a 3501
N1S2 -53 a 280 ab 5b 77 a 161 a 4301
N2SI 207 a 103 b 398 a 236 a 444 a 5291
N2S2 50 a 516 a 292 ab 286 a 326 a 864
Mean 78 277 211 188 270 543
aMeans of three replications. Means followed by a common letter in a column are not significantly different at the 5% level by
LSD .05 (percent loss) = 12.4% and 8.7%;: nd (amount of loss) = 359 kg/ha 279 Kg/ha for DL3-DL1 and DL2-DL1, respe
bDL1 = plots inoculated with R. solani during the previous wet season. DL2 = plots inoculated during the previous wet season +
CNI = 60 kg N/ha, SI = 30 cm, S2 = 20 cm row spacings.
season crops (Shahjahan et al., 1985). Variety
resistance alone has not been successful to contrc
the disease. Consequently, in temperate countries
such as Japan and Korea ShB management ha
resorted to fungicides (Hori, 1984).
ShB has affected grain yield and yield losse
caused by the disease can be significant on differed
cultivars (Boyette and Lee, 1979; Lee and Rush
1983; Marchetti, 1983; Shahjahan et al., 1985
Shahjahan et al., 1986a; Ou and Bandong, 1976
Tsai, 1976; Yu, 1985). It is well established tha
under conditions of close spacing and high level
of nitrogen, ShB becomes very severe Kim et al.
1985; Kozaka, 1975; Ou and Bandong, 1976; Roy
1978; Shahjahan et. al., 1985 but information i
scanty on yield losses relative to level of cro
management, and cultivars with different duratio
in given environments. Efficiency of disease
management should reflect not only the disease
development but also yields and yield losses. Thi
is the main objective of the present study. It i
evident from the results that ShB although severe i
IR58, an early maturing cultivar, was not differed
in intermediate to late maturing cultivars such a
IR62 and IR54 when the infection was initiated a
booting stage (Tables 1 and 2). This suggests tha
if the inoculum level was high and the environment
was conducive during the critical stage of plan
growth, varietal difference in resistance to ShB wa
not a determining factor for its management. Th
losses in IR54 and IR62 were similar or high
than IR58 (Tables 4, 5). When the inoculum level
was low IR58 suffered higher yield loss than th
intermediate and late maturing cultivars, IR54 an
IR62, respectively (Table 6).
Spacing appears to have no effect on Shl
development but the yield and yield losses wer
higher with closer spacing under high nitrogen
High nitrogen stimulates vegetative growth t
produce more tillers. This confirms that under th
same N-level, the influence of spacing was nc
markable (Soepriaman and Palmer, 1977). Th
high tiller formation in wide spacing of plant
resulted in canopy development that provided higl
humidity and shade below the canopy favorable fo
ShB development (Yoshimura and Kurita, 1956
Yoshimura, 1955). Actual yields and yield losse
are results of agronomic practices (N, spacings
and not due to ShB (Tables 4, 5, 6). Conversely
il the loss was low in low N and wider spacing, but
I1 the actual yield was also low.
I, Triphenyltin acetate (Brestan 60 WP) was
s effective in suppressing the development of ShB
and consequently increasing the yield. Plants
s sprayed with Brestan gave higher yield than the
it check. Disease severities were similar suggesting
i, the fungicide (Brestan) promoted plant growth.
; Plants that received Brestan were also healthier and
; delayed in senescence.
it Due to lack of high level of resistance in rice
s to ShB, it has become necessary to find alternative
, means to manage the disease. From the present
,study, it appears feasible to integrate host
s resistance, cultural practices and chemical control.
p Burning infected debris alone is not adequate to
n completely eliminate the sclerotia as source of
e inoculum from the field (Lee and Courtney, 1982).
e Crop rotation is also not effective because the
s pathogen has a wide host range including those
s crops grown during the dry season in the rice field
n (Kozaka, 1975). Biological control of sheath
it blight, although in its rudimentary stage, appears
is promising through seed bacterization (Mew and
it Rosales, 1986). The present study suggests that
it through crop management with minimal fungicide
it spray, the disease may be adequately controlled.
it However, profitability of such an approach should
.s be assessed with a perspective of rice culture types
e under specific environments.
e LITERATURE CITED
BOYETTE, C.D. and LEE, F.N. 1979.
B Reduction in rice yield caused by sheath
e blight. Arkansas Farm Res. 28(3):5.
. HASHIBA, T., UCHIYAMADA, H. and
o KIMURA, K. 1981. A method to estimate
e the disease incidence based on the height of
At the infected parts in rice sheath blight disease.
e Ann. Phytopathol. Soc. Japan 47:194-198.
h HORI, M. 1984. Present status of occurrence and
chemical control of sheath blight in Japan.
)r Japan Pest. Inf. 44:6-10.
s KIM, C.K., DAR, D.S. and H.S. MIN. 1985.
) Ecological studies on rice sheath blight caused
by Rhizoctonia solani. III. Cultural method
and disease development. Korean J. Plant
KOZAKA, T. 1975. Sheath blight in rice plants
and its control. Rev. Plant Prot. Res. 8:69-
EE, F.N. and COURTNEY, M.L. 1982.
Burning rice straw complements other sheath
blight control tactics. Arkansas Farm Res.
.EE, F.N. and RUSH, M.C. 1983. Rice sheath
blight: a major rice disease. Plant Disease
AARCHETTI, M.A. 1983. Potential impact of
sheath blight on yield and milling quality of
short-statured rice lines in the Southern
United States. Plant Disease 67(2):167-175.
VEW, T.W. and ROSALES, A.M. 1986.
Bacterization of rice plants for sheath blight
control. Phytopathology 76:1260-1264.
)U, S.H. 1985. Rice Diseases. Commonw.
Mycol. Inst., Kew, England, 1-369.
)U, S.H. and BANDONG, J.M. 1976. Yield
losses due to sheath blight of rice. Int. Rice
Res. Newsl. 1(1):14.
tOY, A.K. 1978. Horizontal spread of sheath
blight to rice plants in relation to spacing and
nitrogen application. Curr. Sci. 47(9):307-
;HAHJAHAN, A.K.M., SHARMA, N.R.
AHMED H.U. and MIA S.A. 1985.
Spacing x nitrogen rate effect on sheath blight
disease of BR 1 rice. Philipp. Phytopathol.
21(1 & 2):3.
.HAHJAHAN, A.K.M., SHARMA, N.R.,
AHMED, H.U. and MIAH, S.A. 1986a.
Yield loss in modern rice varieties due to
sheath blight in Bangladesh. Bangladesh J.
Agric. Res. 11(2):82-90.
HAHAJAHAN, A.K.M. DUVE, T. and
BONMAN J.M. 1986b. Climate and rice
diseases. In Workshop on impact of weather
parameters on the growth and yield of rice.
7-01 Anril 1986. IRRI. Philinnines
AN, S.Y., and PAL
prison of eight
MER L.T. 1977.
rice varieties with tour plant spacings. Proc.
Ann. Phytopath. Soc. 4:150 (Abstr.).
rSAI, W.H. 1976. Assessment of yield losses
due to rice sheath blight. Plant Prot. Bull.
VATANABE, B., and TAKANO T. 1959. Some
factors in association with the development of
sheath blight disease (caused by Corticium
sasaki (Shirai Matsumoto) of upland rice
plant. Bull. Ibaraki Agric. Expt. Sta. No.
2:142-150 (Japanese with English summary).
(OSHIMURA, S. 1955. On the effect of the
shading upon the susceptibility of the rice
plant to the sheath blight, Hypochnus sasakii
Shirai. Kyushu. Agric. Res. 16:113 (Japan).
(03HIMURA, S. and KURITA, T. 1956.
Epidermical studies of sheath blight on paddy
rice. I. Relation of the microclimate in the
paddy field and the grade of plant density to
the occurrence of sheath blight. Bull. Kyushu
Natn. Agric. Exp. Stn. 4:97-106 (Japan).
(U, C.M., LING, K.C., and OU 'S.H. 1976.
Effect of nutritional and microclimate
conditions on the development of sheath
blight of rice. Plant Prot. Bull. (Taiwan)
- l-1 -., A1 ., L .J. ., .IIU JVIVl.l, U. 171 0.
Effect of temperature on disease development
of rice sheath blight caused by Rhizoctonia
solani. Proc. Assoc. Plant Prot. Hokuriku
226:4-9. (Japanese with English summary).
WIV4LI U11,11LH1 r'%.,L
Sinica 12(3):181-187. (Chime
.U 1A.Y &UF~ 1"A~
CA uuith lpinai~c
NOTE: MULTIPLE I
Cecilia B. Pascual
Supported in part by the Institute of Plant
Bafios (UPLB), College, Laguna, Philippines.
Respectively, University Research Associate
Pathology, UPLB, College, Laguna, Philippines.
In the hot and humid environment of
tropical country like the Philippines, disease
caused tremendous damage and losses in crops
Since croppings usually overlap, disease situation
are exacerbated by the continuous proliferation o
different pathogen forms thereby providing ai
opportunity for genetic recombination and th
emergence of new and possibly more virulen
A number of devastating diseases of sorghur
have been reported in the Philippines (Karganill
and Elazegui, 1973). Among these diseases ar
Rhizoctonia sheath blight caused by Rhizoctoni,
solani Kuhn, Phyllachora disease caused b:
Phyllachora sorghi, gray leaf spot caused b
Cercospora sorghi, target leaf spot caused b:
Helminthosporium sorghicola, zonate leaf spo
caused by Gleocercospora sorghi and grain mold
caused by several species of fungi.
Many of the aforementioned diseases hav
become endemic (IPB, 1988) and occasional;
destructive causing significant losses in sorghum
yield. For instance, Pascual and Raymundo (1988
reported that reduction in yield due to sheath bligh
ranges from 35-42 percent. Resistance to many o
these diseases except to sheath blight has beei
relatively easy to find in many populations. Onl'
recently has a moderate level of resistance to sheatl
blight been detected (IPB, 1988). This note report
on a type of resistance in line CS 621 which ha
been found effective not only against
R. solani but against several sorghum pathogens a
CS 621 is a white-seeded sorghum line witl
semi-compact head. It flowers in 75 days am
reaches a height of about 190 cm. For fou
M LINE CS 621
and A. D. Raymundo
Breeding (IPB), University of the Philippines at Lo
, IPB, and Assistant Professor, Department of Plan
a seasons, during the dry and wet seasons of 198!
s and 1990, CS 621 was evaluated along with othe
;. lines and cultivars at the experimental farms an,
s screenhouse nursery of the Institute of Plan
if Breeding at UP at Los Bafios. The evaluation
n scheme used was as follows: 1 no lesion; 2
e lesions covering up to 10% of the plant; 3 lesion
it colonizing more internodes and covering 10 ti
20% of the plant; 4 extensive invasion of th
n plant, lesions covering 25 to 40% of the plant; 5
a lesions covering more than 40% of the plant up ti
e death of the plant.
a CS 621 showed consistent resistant reaction ti
y sheath blight, tar spot, and gray leaf spot. Durin,
y the 1989 dry season regional trial which wa
y affected by a severe natural infection of tar spot
,t CS 621 sustained the lowest rating of 3 and was th
s only entry among 14 varieties and lines tested tha
had green leaves left at soft dough stage (Table 1)
e At this time, all the other entries had almost all o
y their entire leaves drying up.
m During the 1989 dry season test of CS lines
) CS 621 exhibited resistance to sheath blight, gra;
t leaf spot, and tar spot (Table 2). It had 10.5 ani
f 23.8 percentages of infection of sheath bligh
1 during the dry and wet seasons, respectively, witl
y equivalent ratings of 2 and 3. It showed similar
i ratings of 2 and 3, respectively, for gray leaf spo
s and tar spot during the dry season. It wa
s interesting to note that a number of the CS lines
t especially CS 622, were moderately resistant to on
s or two diseases notably sheath blight but they wer
either moderately susceptible or susceptible to the
i others. The check, UPL Sg 5, was susceptible t4
1 all the diseases considered.
Philipp. Phytopathol. 1992, Vol. 28: 45-48
bld 1. Reaction of different sorghum populations to tar spot during the dry season,
1989-90 at Tranca, College, Laguna.
Entry Rating1 Soft Dough Stage
621 3 Leaves still green
634 4 Leaves drying up
MARC 210 5
MARC 206 5
S Sor 4 5
SSor 1 5
MARC 208 5
1 Sor 2 4
L Sg5 4
based on a rating scale of 1 no lesions; 2 lesions covering up to 10 % of the plant; 3 lesions have
missed through more intcrnodes and covering 10 to 20% of the plant; 4 extensive invasion of the plant,
sions covering 25 to 40 % of the plant; 5 lesions covering more than 40% of the plant up to death of
n'% LCiL V1 u lo Uo. ULa 0 V ZuZ uUIm i, 11E
and wet seasons of 1990 confirmed previ
observations on their level of resistance to she
blight (Table 3). Both lines showed considers
degree of resistance when compared to
susceptible UPL Sg 5.
The discovery of the resistance of CS621
not only significant but unique as well. For
first time, a source of genes imparting consider,
degree of sheath blight resistance, which has b
elusive for a long time, was found. It is unique
the sense that this source, CS 621, turned out tc
resistant likewise to gray leaf spot and tar s1
diseases whose causal pathogens beh
differently. It will be of immense significance
performs as well against other sorghum disease:
ongoing studies at the Department of P
Pathology and Institute of Plant Breeding, UP
Baios hope to find out.
CS 621 has been observed to reduce the
of sheath blight development by 40.3 percent w
compared to the susceptible variety, UPL S
(Pascual and Raymundo, 1990). Sclerc
production and lesion expansion, likewise, v
found to be inhibited. A quantitative pattern
inheritance is indicated (Pascual and Raymur
1991). In an in vitro bioassay, Velasco (1S
found that compounds isolated from CS
inhibited the mycelial growth of R. solani.
CS 621 can serve as a source of mult
resistance genes in a breeding program for I
yield and for stability against diseases. Altho
the diseases abovementioned do not occur
epidemic proportion separately as their degree
severity is influenced to a large extent
geographical and environmental considerate<
their combined effects during a favorable set
can be devastating. In ecosystems where one
more of these diseases can become destructive
where conditions are known to be ideal for yi
CS 621 conceivably can be released as a cultival
iry LITERATURE CITED
ath IPB. 1988. Annual Report, institute of P1
ble Breeding, Univ Philipp., College, Lagu
is KARGANILLA, A. D. and F. A. ELAZEC
the 1973. Sorghum diseases. Upland Ci
ble Annual Rept., Coll. Agric., Univ. Phili
een College, Laguna, Phillippines.
be PASCUAL, C. B. and A. D. RAYMUN]
lot, 1988. Evaluation of resistance and yield
ave in sorghum due to Rhizoctonia sheath bli
f it Phillip. J. Crop Sci. 13: 37-42.
ant PASCUAL, C. B. and A. D. RAYMUN]
,os 1990. Epidemiological parameters
resistance to Rhizoctonia sheath and
-ate blight in sorghum. In Proc. 21st Anniv.
hen Ann. Conv., PCCP, Bacolod City, May 6
g 5 1990.
'ere PASCUAL, C. B. and A. D. RAYMUN]
of 1991. Inheritance of resistance to Rhizocto
do, solani in sorghum. Proc. Ann. Conv., I
90) Crop Sci.Soc. Philipp., Diliman, Que
521 City, Nov. 7-9, 1991.
iple VELASCO, C. K. 1989. Biochemical basis
igh resistance to Rhizoctonia sheath blight
ugh sorghum. Unpublished undergraduate the
in Univ. Philipp., College, Laguna, Philippil
able 2. Reaction of different CS line series to different sorghum diseases, Tranca,
College, Laguna during the wet and dry seasons, 1989-90.
Sheath blight Gray leaf spot Tar spot
% infection Ratingi Ratingi Ratingi
ntry Dry Wet Dry Wet 1989-90 Dry 1989-90 Dry
S621 10.5 23.8 2 3 2 2
S622 19.2 45.1 3 5 2 2
5628 25.5 41.6 3 5 4 3
S631 34.5 4 3
3626 27.0 -4 3
;zAT 11 n ;A 17 A
IDENTIFICATION, ISOLATION, AND PATHOGENICITY
OF ORGANISM(S) CAUSING LEAF DISEASES OF YAM
Respectively, Assistant Professor and Science R
Training Center, Visayas State College of Agricu
Field evaluation was conducted to determ
There were five foliar fungal diseases observed
rust, and marginal leaf spot. Likewise, the cau,
Of the five diseases, anthracnose was found to
Results of the pathogenicity tests prove
Curvularia lunata were pathogenic to yam and c
The survival ability of C. gloeosporioides (
with yam were also investigated. The patl
(Pachyrrhizus erosus) and nami (Dioscorea hispit
In the Philippines, yam is usually grown
small patches of land or as a backyard crop, me
of which are located in the regions of Northe
Mindanao, Bicol, Southern Tagalog and t
Visayas regions (Pido, 1987). Recently, ya
production was reported to increase from 18,1
metric tons/hectare in 1982 to 22,336 meti
tons/hectare in 1987. With the increasing demaj
for this crop, its production has been supported 1
both, government and privately owni
corporations. However, like any other crop, ya
production is limited by various problems like loi
growing season and low yield due to diseases.
Among the numerous fungal disease
attacking yam anthracnose leaf spot caused .1
Colletotrichum sp. holds a particular position
This disease have been found infecting Dioscorn
research Assistant, Philippine Root Crops Research a
Iture, Baybay, Leyte, Philippines
ine the different foliar fungal diseases attacking ya
namely: anthracnose leaf spot, leaf spot, leaf blig]
al pathogen of each disease was studied and identified
be the most prevalent and damaging disease infecti
I that Collectotrichum sp., C. gloeosporioides a
)mbined inoculation of the pathogens resulted to higi
in different species of crop plants and weeds associate
iogen survived and caused infection on singkarr
1973, 1974; Ferguson, 1970). The disease w
observed to greatly affect yam production becau
in of its effect on the photosynthetic activity of t
st plant thereby reducing yield to as much as 5
rn 100% if left unchecked in the field (Degras, et
ie 1983; Nwankiti and Okpala, 1980).
m In the Philippines, there is no information tl
27 will give us an idea on the kind of funj
ic pathogens causing foliar diseases of yam. T
id severity and distribution of these disease were n
>y exactly known although foliar diseases were alwa
;d observed wherever yams were grown. Likewise,
m better understanding of disease symptomatolog
ig pathogenicity, virulence and etiological agents a
needed as good bases toward identification ai
es effective control measures of the disease. T1
,y study was therefore undertaken with the followii
i. objectives: (1) to isolate and identify ai
'a determine the pathogenecity of the cause
md (3) to determine the host range of t
Collectotrichum gloeosporioides. s
MATERIALS AND METHODS
Collection, Isolation, and Identification of i
Field observations were conducted to
determine the occurrence, severity, and
;ymptomatology of foliar fungal pathogens. Plants c
showing disease symptoms were collected and
brought to the laboratory for microscopic g
examination and pathogen isolation.
Free hand sections of diseased tissues were i
prepared and microscopic examinations were made i
o have a preliminary identification of pathogens r
associated with the disease.
To isolate potential pathogens, several
samples of diseased tissues were collected and g
solutions were made using tissue planting and
single spore isolation techniques. For
identification of the different pathogens c
successfully isolated from diseased tissues, c
Appropriate culture media were utilized and the c
norphology of the isolates and other growth e
characteristicss were studied. Identification was c
)ased on Commonwealth Mycological Institute I
CMI) Descriptions for Pathogenic Fungi and r
bacteria and Illustrated Key for Identification of
'lant Pathogenic Fungi (Berett, 1960).
'athogenicity Testing and Interaction of
differentt Isolates 1
To check if the isolates were directly or
directly involved in the development of the
lisease, pathogenicity of the isolates was tested on t
potted yam. a
Two genotypes of yam, namely, IA 010 or c
Cabus-ok and LA-035 or Kinampay, were planted
n pots containing sterilized soil. The plants were /
providedd with stakes, fertilized, watered regularly
.nd sprayed with insecticides.
For the inoculation studies. a snore.
he spore suspension using 450 ml plastic atomizer
-pray gun. Inoculated plants were then kept in
tumid condition by covering with plastic bags for
Observations were made on symptom
development, incubation period, severity and
ncidence of infection at 24 hr interval.
Seasonal Abundance Study
Monthly evaluation of the occurrence of foliar
diseases on yam genotypes at Philippine Root
Crops Research and Training Center (PRCRTC)
germplasm was carried out from 1987-1988 and
1988-1989 cropping seasons. Foliar diseases
identified during the evaluation were noted and the
ncidence or severity of each disease was also
Survival Ability of Collectotrichum
,loeosporioides on Alternate Hosts
Weed species associated in yam field and
theirr crops (Table 1) were planted in small pots
containingg sterilized soil. Host range study was
conductedd under screenhouse condition. The
experiment was laid in completely randomized
design (CRD) with three replications. Data
gatheredd include symptom development, incubation
)eriod, incidence and severity of infection.
RESULTS AND DISCUSSION
Foliar Diseases of Yam: Symptomatology and
Results of the present study revealed, that
here were five foliar fungal diseases found
attacking yam in the field. They are listed and
Lnthrnennrc TIPnf Qnnt
The antnracnose lear spot was cnaractrnzd i
by the appearance of small, round to irregula
brown spot on the abaxial side of mature leaves
Initially, the spots, about 2mm in diameter, wer
subcircular and dark brown usually found along th
leaf margin. As the disease advanced, the spot
enlarged, spread and coalesced forming large
necrotic spots and sometimes developed concentric
circles of light and dark brown. As infection
became more severe, epidermal blackening ani
withering of infected leaves occurred. Both mature
and young leaves were susceptible, but infection
usually started for the lower leaves and move
Infection on the steam generally occurred as
result of severe leaf infection but direct penetration
of the fungus near the terminal bud or through th
petiole may also cause infection. In severe cases
defoliation proceeded to the top resulting in th
death of the plant and failure to form rhizomes o
tubers. Infection and development of symptom
can be completed in 96 hr. High humidity favored
infection and the disease spread rapidly in period o
Isolation studies revealed that man'
organisms were involved in the disease syndrome
with C. gloeosporioides as the main organism
causing the disease.
Both mature and young leaves were attacked
but frequently the former were more susceptible
Initial symptoms included yellowish browi
punctiform or small isolated spots on any part o
the leaf. Younger spots measured to 1.0 mm ii
diameter, characterized as superficial sunken, small
or dotted yellowish brown spots and grayish ti
dark brown at the center. As the disease
progressed, the center of the spots became
depressed and scorched, forming zonation witl
holes at the center. Spots formed at the lower o
older leaves were irregularly shared with larg
brown spots ranging from 8.0 to 57.0 mm ii
diameter and water-soaked at the margin. Th
center of depressed spots turned dark brown witl
necrotic areas within the spots. The affected vein
appeared dark brown. Fruiting bodies or mycelia
I Table 1. ilant species usea as noss ou
isolated from yam.
Common Name Scientific Name
* Crop Species
* Bush bean Phaseolus vulgaris
S Cor Zea mays
Eggplant Solanum tuberosum
Mungbean Vigna radiata
Nami Dioscorea hispida
S Peanut Arachis hypogea
1 Pepper Capsicum annuum
Singkamas Pachyrrhizus erosus
a Sorghum Sorghum bicolor
S Stringbeans Phaseolus vulgaris
Tomato Lycopersicum esculentum
S Kudzuo Calopogonium mucunoides
S Kulitis Amaranthus spinosus
S Sili-silihan Cleome rutidosperma
1 Kolasi Murdannianudiflora
f brenan (L.)
Kamu-kamuti Ipomoea triloba L.
Obod-obod Cyparus imbricatus
Kanaka Euphorbia heterophylla L.
Magatas Euphorbia hirta L.
S Dakayang Echinochloa colona
Agingay Rottboellia exaltata
d Olasiman Protulaca oleracea
The causal pathogen of leaf spot wa
identified as Curvularia lunata.
e Leaf Blight
The disease which was characterized by larg
Swater-soaked lesions with no distinct margi.
usually attacked lower or older leaves. As th
e disease advanced, a concentric light and brow
color zonation was often observed. Within th
s light brown, large collapsed spots, light brown
dried spots bordered with dark brown were als,
found. In the later stage of the disease, the whol
Philipp. Phytopathol. 1992. Vol. 28: 49-55
The suspected pathogens that cause the
disease included Colletotrichum sp.,
Botryodiplodia theobromae and Rhizoctonia solani.
Among the three pathogens, only B.
theobromae and Colletotrichum sp. were tested for
their pathogenicity. Both were found pathogenic,
showing the same symptoms in yam leaves as
Rust was considered a minor disease. It was
easily distinguished by the formation of thickened
orange specks on the leaf surface. Disease
occurrence was usually observed during dry to wet
The causal organism was identified as Uredo
dioscoreicola (= Uredo dioscoreae-alata Racib). It
was first observed from leaves of D. alata
collected in Manila in 1912 and was characterized
by the formation of internal teliospores submerged
in a gelatinous matrix. A sterigmata was produced
from each cell of the basidium and extended to the
surface of the matrix where a single basidiospore
was liberated (Cook, 1978).
Pathogenicity test was likewise conducted for
Uredo dioscoreae and it was found infective and
cause the same symptoms as described above.
Marginal Leaf Spot
Generally, the symptoms of the disease
exhibited reddish punctiform spots on the upper
leaf surface during the earlier stage of infection.
Later, these small spots coalesced and formed large
dark brown lesions bordered by reddish coloration.
As the disease progressed, spots fall-off.
The pathogens found associated with the
disease were Pestalotiopsis sp., Alternaria sp.,
Stemphylium sp., Fusarium sp., and Cercospora
sp. However, no pathogenicity test was conducted
for all 4 pathogens.
Results of the pathogenicity tests conducted
using C. gloeosporioides, C. lunata and
Colletotrichum sp. showed that the 3 isolates were
pathogenic to yam plants (Table 2). Furthermore,
the findings suggested that combined inoculation of
the three isolates gave the highest number of lesion
per leaf compared to inoculation by single
organisms. This suggests the possibility that
serious infection may occur with the presence of
secondary organisms specifically Colletotrichum
sp. and C. lunata.
Seasonal Abundance, Severity and Incidence of
Five Foliar Diseases
In order to determine the predominating foliar
diseases of yam and their severity and distribution,
monthly evaluation of the different yam genotypes
in the PRCRTC germplasm collection was
conducted for a period of 3 years (1987, 1988,
Results of the 3-year evaluation showed that
among the 5 foliar fungal diseases identified
earlier, anthracnose leaf spot was the most
prevalent and damaging disease infecting yam
(Table 3). As shown in Table 3, incidence of the
five foliar fungal diseases increased with time.
During the first year of evaluaion, anthracnose
incidence for instance increased from 5.71% to
61.63%. The following year, an increase (24% to
98%) in disease incidence was noted. It was also
worth mentioning that during the third year of
evaluation, 99.2% of the genotypes were found
infected with anthracnose during the first month of
rating and starting September, 100% incidence was
recorded. However, for leaf spot, marginal leaf
spot and leaf blight, a decreasing trend in
percentage disease incidence was observed. This
implies that competition among pathogens present
in yam leaves was taking place. As C.
gloesporioides dominates, the population of other
pathogens decreased. Consequently, percentage
disease incidence decreased.
Rust infection was noted to be high during the
second year (1988), where 86% of the total
genotypes evaluated were found infected even at an
earlier stage of plant growth.
Generally, there was an increasing incidence
for all the diseases monitored. Once infection was
initiated, disease incidence progressed with time
until it reached maximum.
In terms of disease severity, results revealed
that it was higher in the area were the same crop
rnmpp. rnytopathol. 199I. Vol. 24: 49-55
Table 2. Period of disease incubation and th
Curvularia lunata 6.1
Colletotrichum sp. 4.2
C. gloesporioides +
C. lunata +
Colletotrichum sp. 8.0
Distilled water 0.0
a Average of 50 leaves.
Table 3. Percentage disease incidence of
germplasm, ViSCA, Baybay, Leyte
Month ALS LS
July 5.71 1.22
Aug 9.79 3.26
Sept 21.63 21.63
Oct 40.40 28.16
Nov 56.73 47.75
Dec 61.63 47.75
July 24.00 21.63
Aug 34.00 28.16
Sept 86.00 34.00
Oct 98.00 34.00
Nov 98.00 58.00
Dec 98.00 58.00
July 99.20 64.00
Aug 99.60 37.20
Sept 100.00 36.40
Oct 100.00 39.00
M 0nn no 3 .00
five fungal diseases infecting yam in the PRCR
e Incidence (%)
MLS LB R
1.22 1.22 0.0
2.85 3.26 0.40
13.06 13.88 4.90
28.16 14.70 4.90
47.75 40.81 32.65
58.77 50.06 43.67
16.00 4.00 20.00
28.16 14.70 86.00
80.00 34.00 86.00
86.00 34.80 86.00
86.00 34.80 86.00
86.00 40.70 86.00
43.60 26.40 0.00
27.20 4.00 3.60
26.80 4.00 3.20
28.16 5.70 3.84
28.16 5.70 25.60
as continiously planted. In addition, it was DI
)served that typhoon and heavy rains contributed
the rapid development and spread of the foliar
ngal diseases of yam. The rate of disease spread
creased towards the later stage of plant growth
id finally severe infection was noted when plants
ere about to be harvested.
Table 4 shows the percentage incidence of PE
Lthracnose leaf spot evaluated for a period of 5
ars (1987-1991) taken every 8-9 months after
wanting. In 1989, a lower incidence (61.63%)
as noted and in 1991 all the genotypes evaluated HI
ere infected with the disease.
ost Range Study
Results of the inoculation revealed that out of
2 different plant species used, only singkamas
. erosus) and nami (D. hispida) were infected by
The findings revealed further that although
olletotrichum species are widely distributed all
rer the world (Hadden and Black, 1989), some
Alates from one crop species do not necessarily N)
feet other species and that similarities in
mptoms exist on diseases caused by
NON, 1973. Annual Report. Root and Tuber
Improvement Programme. IITA, Ibadan.
NON. 1974. Annual Report. Root and Tuber
Improvement Programme. IITA, Ibadan.
4RNET, H.L. 1960. Illustrated genera of
Imperfect Fungi. Burgess Publishing Co.
DOK, A.A. 1978. Diseases of tropical and
subtropical vegetables and other plans.
McMillan Publishing Co. Inc., New York.
%1TTVCCV Tir. 1 a17 V-,> A ,, A ,..,t
Philipp. Phytopathol. 1992. Vol. 28: 49-55
GRAS, L., R. ARNOLIN, C. SUARD and R.
POITOU. 1983. Selection of Dioscorea
alata Cultivars of low susceptibility to
anthracnose (Colletotrichum gloeosporioides).
Proc. 6th Symp. ISTRC. CIP, Lima, Peru.
RGUSON, T.U. 1970. The Status and Future of
Yams in Carribbean, Proc. 2nd Symp. Trop.
Root Tuber Crops, Hawaii, 2:28-30.
JDDEN, J.F. and L.L. BLACK. 1989.
Anthracnose of pepper caused by
Colletotrichum spp. of Vegetable Crops. A
disease management. (Persley, DM.,
R.O'Breen and J.R. Syme eds., Department
of Primary Industries, Queensland Gov't.
Info. Services: 66p.
VANKITI, A.O. and O.B. ARENE. 1978.
Diseases of yam in Nigeria PANS 24, 486-
VANKITI, A.O. and E.U. OKPALA 1980.
Anthracnose of water yam in Nigeria. Proc.
First Triennial Root Crop Symp. Int. Soc.
Trop. Root Crops. Ibadan, Nigeria. 166-
)O, N.L. 1987. Crop characteristics,
production and storage. In Uba: A guide to
its culture and use Pido, N.L. and Pepino,
M.M. (Authors). Phil. Root Crop
Information Service (PRIS). 78 p.
Table 4. The incidence of anthracnose leaf spot ir
Disease incidence taken 8-9 months for every croppi
1 PRCRTC yam germplasm (1987 to 1991).
ABSTRACTS OF PAPERS PRES
CONVENTION OF PEST MANAGEMI
(PMCP); 27-30 APRIL 1992,
SURVEY OF VIRUS AND VIRUS-LIKE
DISEASES OF CITRUS IN THE HIGHLANDS
OF NORTHERN LUZON. J.M. Ochasan, M.B.
Guerrero and E.A. Verzola. Bureau of Plant
Industry, Guisad, Baguio City.
A survey was carried out in the highland
provinces of Northern Luzon in 20 orchards.
Identification was done through biological indexing
using specific indicator plants. Aside from citrus
tristeza virus, which was known to be widely
distributed in the area, citrus greening disease was
detected and its insect vector, Diaphorina citri
Kuway. was noted in some areas. Another disease
called woody gall/vein enation, previously
unreported in Philippine citrus was found in two
orchards. However, its economic importance is yet
to be assessed as they do not seem to cause major
damage even on susceptible cultivars such as
DISEASE REACTION OF PROMISING
IRRIGATED LOWLAND RICE SELEC-
TIONS. D.L. Adorada, T.U. Dalisay, A.M.
Sinohin and D.B. Lapis. PhilRice-UPLB, College,
Reactions of ten promising irrigated lowland
rice selections from the National Cooperative Rice
Performance Test (NCRPT) were evaluated against
major rice diseases during the 1991 dry and wet
seasons to be used as basis on the release of
varieties for commercial propagation.
IR52341-60-1-2-2 and IR52287-15-2-3-2
were consistently resistant to rice blast and
bacterial blight for the two seasons. Except for
IR54883-152-3- and PR22909, the rest of the
entries were found consistently resistant to bacterial
ENTED DURING THE ANNUAL
ENT COUNCIL OF THE PHILIPPINES
TAGAYTAY CITY, CAVITE
blight. Against sheath blight, no entry was found
resistant and only PR22909 was rated intermediate
in both seasons. No entry was rated resistant nor
intermediate to tungro for both seasons.
IDENTIFICATION OF SOFT ROT ERWINIAS
INFECTING POTATOES (Solanum tuberosum
L.) IN THE PHILIPPINES. Vivian M. Laman-
ag and R.B. Valdez. Department of Plant
Pathology, UP at Los Bafios, College, Laguna.
Morphological, cultural and biochemical tests
of 34 isolates of soft rot Erwinias from white
potato in the Philippines showed that 13 were
Erwinia carotovora subsp. atroseptica (Eca), and
7 were Erwinia chrysanthemi (Ech). All the
cultures showed identical characteristics in all the
tests employed except in the production of acid
from trehalose and in the production of indole.
There was a predominance of Ech in Bukidnon
while Ecc and Eca were prevalent in Benguet
province including Baguio City.
ANALYSIS OF DIVERSITY IN POPULA-
TION OF Helminthosporium sativum PAMMEL,
KING, & BAKKE. Cecilia B. Pascual and A.D.
Raymundo. Institute of Plant Breeding and
Department of Plant Pathology. U.P. at Los
Bafios, College, Laguna
Diversity in population of H. sativum,
collected from wheat growing areas in Northern
Luzon and from College, Laguna, was measured
based on the following parameters; lesion length,
lesion number, incubation period, spore size,
number of septa, colony size, toxin production,
and protein banding pattern. Estimation of
divprcitv '1- an. mth th-4, ml0' lt;ro;tn m.t..rln
L:nn.- .,,rLd*J 106Q V.nl 122 4&.2
principal component analysis, cluster analysis, and
multiple regression analysis.
Significant differences among isolates were
observed in all the parameters considered.
Principal component analysis showed that the first
component, which accounted for almost half of the
total variance, was dominated by number of septa,
spore size, lesion length, and toxin production.
Average linkage cluster analysis using each of these
four parameters, revealed three main clusters of
isolates. Significant correlation coefficients,
involving several parameters, were obtained.
FIELD EVALUATION OF NEMATOPHA-
GOUS FUNGI FOR THE BIO-CONTROL OF
POTATO CYST NEMATODE, Globodera
rostochiensis WOLL. IN ATOK, BENGUET.
R.A. Zorilla and R.G. Davide. Department of Plant
Pathology and National Crop Protection Center,
U.P. at Los Bainos, College, Laguna.
Field experiments conducted in a severely
cyst-infested area in Atok, Benguet revealed that
Paecilomyces lilacinus (BIOCON) and Peru
isolates consistently and significantly reduced
potato cyst nematode population resulting in more
than 50% increase in tuber yield. The other P.
lilacinus isolates and nematophagous fungi,
Metarhizium anisopliae, Penicillium oxalicum and
P. anatolicum gave comparable nematode control
and yield with nematicide Carbofuran 3G
treatment. The tuber-dip treatment of P. lilacinus
alone gave the most effective control of cyst
nematode and the highest increase in yield (70%).
However, combination of P. lilacinus with other
fungi did not give any disadvantageous effects. On
the other hand, increasing the level of spore
concentration of all fungal isolates tested from 2
million spores/ml to 8 million spores/ml in tuber-
dip treatment resulted in higher percentage cyst
nematode control and higher tuber yield increases.
Generally, the nematode control and tuber yield
from the fungal treated plots were significantly
higher than those in the nematicide treated-plots
and the untreated (control) plots.
Attempts to recover the nematophagous fungi
using the soil dilution method from the treated field
gave positive results. The fungus recovery was
high in the 10-1 dilution. This indicates that these
nematophagous fungi can survive and reproduce in
the soil and can remain effective in controlling the
nematodes for a longer period of time compared to
BIOCONTROL EFFICIENCY OF SOIL
FUNGI AGAINST ROOT-KNOT NEMA-
TODE, Meloidogyne incognita OF TOMATO.
R.A. Zorilla and R. G. Davide. Department of
Plant Pathology and National Crop Protection
Center, U.P. at Los Bafios, College, Laguna,
The effectiveness of the soil fungi
Paecilomyces lilacinus, Penicillium oxalicum,
Penicillium anatolicum and Metarhizium anisopliae
were evaluated against root-knot nematode,
Meloidogyne incognita under laboratory and
Laboratory assay indicated that P. lilacinus
(BIOCON), other isolates of the same species and
other soil fungi tested were capable of parasitizing
and infecting M. incognita eggs and larvae. All
fungal isolates significantly reduced egg hatching
resulting higher percentage mortality of the
nematode larvae compared with those in the
Extracts of fungal isolates [P. lilacinus (5
isolates), P. anatolicum, P. oxalicum, M.
anisopliae] tested under greenhouse conditions
were effective in reducing root-knot nematode
infection. Low gall indices, low gall counts and
low egg mass production were observed.
Increasing the spore concentration of all fungal
isolates from one million spdres/ml to 4 million
spores/ml gave comparable effects with the
Carbofuran 3G nematicide treatment and in some
cases even better for the biocontrol of tomato root-
Philipp. Phytopathol. 1992. Vol. 28: 56-68
BACTERIAL CROWN tALL: A Ir vw
DISEASE OF ROSE IN THE PHILIPPINES.
R.G. Bayot; M. Renon, and T. Cadatal. National
Crop Protection Center, UP at Los Bafios.
A disease resembling bacterial crown gall was
recently observed on stems of roses planted in the
garden of Mr. Tomas Cadatal at Hillside, College,
Laguna. Approximately 10% of the plants had
galls. The galls ranged from 1 to 4 cm in
diameter. Since bacterial crown gall caused by
Agrobacterium tumefaciens is not known to be
present in the country, it was deemed necessary to
determine the cause of the disease.
The pathogen was isolated successfully into
pure culture using potato-dextrose agar (PDA).
White, domed, circular, mucoid colonies
developed on PDA 48 to 72 hr after streaking.
Representative colonies were inoculated to young
tomato seedlings (cv. VC-11-1) by wounding the
succulent stem with scalpel and despositing a
loopful of bacterial growth onto fresh wounds.
Typical crown gall symptoms developed on tomato
stems 3 wk after inoculation. Gall size increased
up to 2.5 cm after 12 wk.
These results suggest that the stem gall of rose
in the Philippines is caused by A. tumefaciens.
The disease was probably introduced into the
country through planting materials imported rose
cuttings latently infected with the crown gall
EFFECT OF DIFFERENT FER'LIZER LE-
VELS ON THE INCIDENCE AND DEVELOP-
MENT OF BLACK STRIPE OF RUBBER.
Teresita B. Bayaron and S. Rivera, U.S.M.,
The effect of four levels of complete fertilizer
on black stripe of rubber caused by Phytophthorn
palmivora was investigated. The experiment was
laid out in randomized complete block design
replicated three times. The rates used were 2.0,
1.5, 1.0 and zero kg/three/year. Six months
thereafter, the effect were determined for two
Prior to fertilizer application, the trees were
assessed of black stripe infection. These trees
showed symptoms of brown to black lesions on top
the tapping panel.
Application of complete fertilizer at different
levels significantly reduced the severity of black
stripe. When the application of fertilizer was
increased to 2.0 kg/tree/year, the infection was
significantly reduced to a severity rating of 1.26.
Using 'the farmers recommended rate of 1.5
kg/tree/year had lowered the infection to 1.46.
Further, infection of black stripe was not
significantly different between the farmers rate and
those trees applied with 1.0 kg/tree/year resulting
to a rating of 1.67. Infection of untreated trees
were significantly higher with a mean of
Black stripe was likewise suppressed with the
continued fertilizer application. Mean infection
rating of 1.60 during the first applications was
significantly decreased to 1.51, 1.45 and 129 after
the second, third and fourth applications.
Fertilization, therefore is necessary for the
control of black stripe disease of rubber.
EFFICACY OF Paecilomyses lilacinus
ISOLATES FOR THE CONTROL OF ROOT-
KNOT NEMATODE (Meloidogyne incognita) IN
SWEET POTATO. Celia D. Galano and R.M.
Gapasin. Department of Plant Protection, ViSCA,
The application of different P. lilacinus
isolates grown grown in water hyacinth substrate,
50 days after M. incognita egg inoculation
increased fresh vine and fibrous root weights by
32.6-36.2% and 29.6-35.1%, respectively over
that of the untreated control. On the other hand,
chicken manure and ethoprop-treated plants had an
increase of 43.0 and 37.9% and 29.9 and 18.6%,
The mean number of root galls, egg masses
and nematode population in fibrous roots and soil
Philipp. Ihytopathol. 1992. VoL 28: 56-68
produced in plants applied with P. lilacinus isolates
ranged from 27.8-42.0, 40.9-58.1, 8.4-11.5 and
392.0-800.8, respectively. The Matalom isolate
gave the lowest mean root galls (27.8) and egg
masses (40.9) produced per root system and the
highest percent egg mass reduction of 55.
However, it did not significantly differ from the
rest of the isolates. Chicken manure-treated plants
iad mean root galls of 28.8 and egg masses of
40.3. Egg mass reduction was 55.7%. Ethoprop
gave the lowest number of galls (4.2) and egg
masses (6.2) compared to other treatments.
Percent reduction based on egg masses produced
The results showed that the efficacy of P.
!ilacinus in reducing root-knot galls, egg masses
md nematode population was comparable to
chickenn manure but not with ethoprop.
COMPARATIVE ANALYSIS OF PARTIAL
RESISTANCE OF PEANUT TO Cercospora
2rachidicola HORI AND Cercosporidium
personatum (BERK. & CURT.) DEIGHTON.
R.A. Paningbatan and O.S. Opina. Department of
Plant Protection, ViSCA, Baybay, Leyte and
Department of Plant Pathology, UP at Los Baios,
Components of partial resistance of peanut
[BPI P9, UPLB Pn4, PI 259747, PI 350680, EC
764466 (292)] to Cercospora arachidicola Hori
and Cercosporidium personatum (Berk. and Curt.)
Deighton were examined based on one cycle of
infection process in pot experiments. Relationship
of these components to different parameters of
diseases progress in the field was established.
Across cultivars, C. arachidicola exhibited 4-
day shorter incubation period, 6-day shorter LP50
(mean latent period of 50% lesions), 13 day earlier
to reach the standard 5-mm2 lesions, and fourfold
less efficient in sporulation per unit lesion area
than did C. personatum. Partial resistance of
peanut cultivars to both pathogens manifested as
prolonged incubation period, prolonged LP50 and
prolonge period to attain a standard lesion area,
orrelated with decreased end-of season disease
severity, AUDPC, and with increased time to reach
0% disease severity (T50) but not with apparent
ifection rate. Because they showed consistent
ranking of peanut cultivars, end-of-season disease
everity, AUDPC, and predicted time to reach
0% level of disease severity were considered
letter parameters to assess the level of resistance in
INDIGENOUS FUNGAL PATHOGENS WITH
POTENTIALL TO CONTROL Sphenoclea
eylanica. R.G. Bayot and M. Renon. National
.rop Protection Center, UP at Los Baiios, College,
Sphenoclea zeylanica is one of the major
owland weeds in the Philippines. There are
populationss of this weed in some parts of the
countryy that are reportedly becoming resistant to 2,
[-D. It has also been observed that S. zeylanica is
>eing attacked by leaf mold and leaf blight
diseases. This study was conducted to determine
he infectivity of leaf mold and leaf blight
>athogens to S. zeylanica and selected economic
S. zeylanica plants with mold and blight
symptomss were examined microscopically and the
fungal pathogen isolated into pure culture on potato
lextrose agar (PDA). Pathogenicity of the isolates
vas tested on S. zeylanica seedlings in the
grenhouse. Selected economic crops were also
noculated with the fungal isolates.
The two fungal pathogens causing leaf blight
ind leaf mold of S. zeylanica were tentatively
identified as Alternaria sp. and Cercosporidium
;p., respectively. The fungus isolated from leaf
nold-infected leaves did not sporulate on PDA,
)atmeal agar and sterilized stems of S. zeylanica at
-oom temperature (28-31C). Leaf mold symptoms
appeared 12-14 days after spraying S. zeylanica
seedlings with spores of leaf mold pathogen
gathered from heavily infected leaves. Disease
progress of leaf mold on young plants was slow.
Philipp. Phytopathol. 1992. Vol. 28: 56-68
Alternaria sp. sporulated well on FDA al
room temperature. Spores germinated in about (
hours and penetrated leaf tissues directly 12 to 1(
hours after inoculation. S. zeylanica seedlings
developed blight symptoms in only 1 to 2 day.
after spraying with spores of Alternaria sp. al
concentration of approximately 30,000 spores per
ml under greenhouse conditions. Inoculatec
seedlings were dead after 5 days. Culture filtratf
of the pathogen did not produce blight symptom!
when applied as drops on leaves or as spray or
young S. zeylanica seedlings. Culture filtrate was
prepared by growing Alternaria sp. in flash
containing potato-dextrose broth and filtering th
liquid after 14 to 21 days.
Both fungal pathogens did not infect rice
corn, wheat, sorghum, okra, tomato, potato
soybean and mungbean. All seedlings wert
sprayed twice (at weekly interval) with sport
suspension of the pathogen and incubated in mois
chamber for two days.
These results suggest that Alternaria sp. ha!
great potential as biocontrol agent against S.
zeylanica. However, more rigid tests must bt
undertaken to ensure that the biocontrol agent i,
safe to humans, economic crops, and tht
EFFECT OF SOIL ORGANIC AMENDMENTS
WITH Trichoderma harianum RIFAI O1
SCLEROTIUM STEM ROT DISEASE Of
TOMATO. H. La Rosa, D. Paderes, and A.
Lalap. Central Luzon State University, Muno,
Trichoderma harzianum produced as compose
fungus activator (CFA) at CLSU Mass Production
Center, funded by PCARRD-DOST Project was
screened for its biological control activity against
Sclerotium rolfsii, causing stem rot disease of
CFA consisted of T. harzianum grown in a
mixture of ipil-ipil and sawdust. Application of
different levels of CFA on S. rolfsii infested soil
chnwiAi a hiohlv cionifiarnt incrpae, in thep niimhpr
of tomato that survived at 14 and 21 days after
transplanting. Plants treated with different levels
of CFA alone provided the same number of
survived plants similar to uninoculated control.
In vitro test for antagonism suggested that
CFA has no effect on sclerotial germination.
However, mycelial growth was suppressed by T.
harzianum 2 days after seeding followed by total
colinization on germinated selerotia.
SURVEY AND IDENTIFICATION OF
SEEDBORNE FUNGI OF DIFFERENT
VEGETABLE CROPS. Elenita G. Sison, Jane S.
Bartolini, and Maribel Querijero. Bureau of Plant
Seed samples were submitted at the Seed
Quality Control Services for seed health tests using
the blotter method. Seeds were incubated for 12
hours at NUV and 12 hours darkness. After 7
days, seeds were examined under the microscope;
and range of infection was computed and recorded.
There were 37 species of vegetable seeds
tested for seed health from January to December
1991. Several species of seedborne fungi were
identified such as Aspergillus spp.. Alternaria sp.,
Botrytis sp., Cercospora sp., Curvularia spp.,
Chaetomium sp., Cephalosporium sp.,
Cladosporium sp., Colletotrichum sp., Fusarium
spp., Helninthosporium sp., Macrophoma sp.,
Macrophomina sp., Myrothecium sp.,
Nigronervosa sp., Phoma sp., Penicillium sp.,
Phomopsis sp., Rhizopus sp., Sremphyllum sp.,
Infection ranged from 0.5 100%.
DIVERSE SOURCES OF RESISTANCE TO
Peronosclerospora philippinensis (WESTON)
SHAW IN CORN. B.J. Calilung Jr. and A.D.
Raymundo. Institute of Plant Breeding and
Department of Plant Pathology, U.P. Los Bafios,
Philipp. Phytopathol. 1992. Vol. 28: 56-
Institute of Plant Breeding sifice the 1960's ha
focused on Philippine downy mildew caused b
Peronosclerospora philippinensis (Weston) Shaw
A number of cultivars, including the DMR (down
mildew resistant) series and IPB Var. 1, wit
considerable resistance to the pathogen, have bee
released. Resistance of these cultivars have bee:
derived primarily from the local variety, Tiniguib
Due to the existence of other Peronosclerospor
species and to recent reports regarding apparent
variation in P. philippinensis, continuous screening,
and evaluation of diverse germplasm are beni
From disease nursery tests in several
locations, various genotypes obtained from othe
countries and several indigenous varieties fron
corn-growing areas in the country, have beei
identified as alternative sources of genes. Some o
these exotic genotypes have earlier been reported a
resistant to either P. sacchari or P. sorghi.
IDENTIFICATION, BIOASSAY, ANI
EVALUATION OF MYCORRHIZA FOR UTI
LIZATION IN CASSAVA AND SWEE1
POTATO PRODUCTION. M.K. Palomar an<
F.L. Loreo. Department of Plant Protection
ViSCA, Baybay, Letye
Survey and collection trips were conducted t(
determine the prevalence of mycorrhiza and t(
identify the mycorrhizal species associated witt
agricultural crops. The survey showed thai
mycorrhizal fungi present in many areas in Leyt(
were found in vegetable and plantation crops
including cassava and sweet notatn I noa
Philipp. Phytopathol. 1992. Vol. 28: 56-68
gloesporioides. However, when incubated for were introduced after rust pustules had been
longer period of time, appresoria were formed. formed.
When selected potential microbial antagonists
were tested on mango fruits for their effect on
anthracnose development, several isolates delayed EFFECT OF LATEX ON. POSTHARVEST
infection to some extent. However, no isolate was PATHOGENS OF FRUITS. L.L. Ilag, J. Villa,
able to prevent or totally stop disease development. Nerissa Banasihan and Josefina Opefia.
Leaf infection was also delayed by some isolates. Department of Plant Pathology, U.P. Los Bafios,
PARASITES OF THE PEANUT RUST The latex that oozes out when newly
FUNGUS. L.D. Valencia and Lina L. Ilag. harvested banana, mango, and papaya fruits are
Department of Plant Pathology, U.P. at Los injured, was found to variously affect fruit-rotting
Bafios, College, Laguna. pathogens.
Latex from ripe, "turning", and green papaya
Microbes were isolated from peanut (Arachis fruits stimulated conidial germination of
hypogeae L.) leaves, with and without rust pustules Colletotrichum gloeosporioides and Rhizopus sp.,
and tested for antagonistic effects on Puccinia both pathogens of papaya. On the other hand,
arachidis Speg. causing leaf rust of peanut plants, latex inhibited the germination of spores of
Microscopic observations revealed that among the Fusarium sp. which causes papaya fruit rot.
potential antagonists tested for their effect on the Mango latex strongly enhance germination of
germination of pathogen spores, two unidentified conidia of C. gloeporioides, the cause of mango
bacterial isolates as well as Fusarium sp., D. anthracnose.
hansenii and Darluca sp. effectively inhibited the Latex from banana crown reduced percentage
growth of pathogen germ tube. Fusarium sp. and germination and germ tube length of F. roseum and
Darluca sp. were observed coiling around the F. semitectum but it stimulated germination of
uredospores of P. arachidis while D. hansenii and spore. Thielaviopsis paradoxa. These fungi cause
the bacterial isolates were noted to cluster around banana crown rot.
uredospores and germ tube of the pathogen. Some The addition of papaya fruit extract to the
cells of the yeast, D. hansenii, appeared associated latex negated the inhibitory effect of latex on the
with disintegrated germ tubes/hyphae of the germination of Fusarium sp.
pathogen and were sometimes observed inside
hyphae of P. arachidis.
Preliminary in vivo test using peanut leaflets MICROBIAL ANTAGONISTS OF THE PAPA-
in the laboratory showed that Darluca sp. and D. YA FRUIT ROT PATHOGENS, J. Villa and
hansenii delayed rust development as showed by a Lina L. Ilag. Department of Plant Pathology, U.P.
lower disease rating compared to the control with Los Bafios, College, Laguna.
no antagonist added. Both isolates were also
effective in reducing the number of rust pustules Twelve bacteria and two yeasts isolated from
and number of sporulating pustules when applied at the surface of apparently healthy papaya fruit by
the same time or mixed with the pathogen. On dilution plating method were ineffective when
naturally rust-infected leaflets, Darluca sp. and tested against Fusarium sp. and Colletotrichum
D. hansenii reduced the total number of pustules gloeosporioides in challenge culture plates.
and the number of sporulating pustules 20 days Rhodotorula mucilaginosa (B2), Torulopsis
after antagonist application. The two fungi were candida, Debaryomyces hansenii, Saccharomyces
also effective in delaying infection even when they chevaliere, S. cerevisiae and Cheese isolate m all
Philipp. Phytopathol. 1992. Vol. 28: 56-68 63
showed no zones of inhibition when challenged to relate loss of yield and yield components to
with Fusarium sp. and Colletotrichum epidemiological parameters of pest dynamics and
gloeosporioides in potato dextrose agar. on calibrating and validating a pest-coupled version
Yeast isolates A8 and All, obtained from of the CERES rice model.
papaya fruit, significantly reduced rotting of fruit
in the presence of Fusariums sp. by 70 and 55
percent, respectively after 7 days of incubation. TUNGRO VIRUSES IN VOLUNTEER RICE
Isolates A8 reduced infection of C. gloeosporioides PLANTS. ER. Tiongco, N.G. Fabellar, P.S.
by 41 percent after 7 days of incubation. A Teng, and H. Koganezawa. IRRI, Los Baiios,
bacteria isolate 001 from papaya controlled C. Laguna.
gloeosporioides infection by 36 percent 7 days
after inoculation. The rice tungro viruses are reported to infect
The six other yeast isolates tested against C. rice stubbles, weeds, and wild rice species which
gloeosporioides gave no significant reduction in may then serve as sources of inoculum for infection
infection. of succeeding rice crops. This study was
conducted to determine whether the volunteer rice
plants that germinated from seeds spilled during
EFFECTS OF MULTIPLE PESTS ON YIELD thresing harbor the rice tungro bacilliform virus
COMPONENTS AND YIELD COMPONENTS (RTBV), rice tungro spherical virus (RTSV), and
AND YIELD OF RICE G.V. Maningas, H.O. the vector leafhoppers.
Pinnschmidt, and P.S. Teng, Plant Pathology More RTSV infection was obtained in plant
Division, International Rice Research Institute samples collected from Iloilo and Sultan Kudarat
(IRRI), Los Bailos, Laguna. where only few sites had infection of RTBV. Low
infection of both RTBV and RTSV was obtained
The combined effects of leaf blast, panicle even though testing the plants in batches increases
blast, sheath blight, bacterial leaf blight, and insect the chance of detecting double infection. No
pest on yield of rice cv IR72 were studied in three infection was obtained in Camarines Sur. More
irrigated lowland field experiments at IRRI (WS leafhopper vectors were collected in Sultan Kudarat
1990, DS 1991, and WS 1991). Different than in Camarines Sur and Iloilo although vector
scenarios of pest infestation were created by insects were present in most sampling sites.
inoculation and/or application of pesticides. Results showed that volunteer rice plants are
Panicle blast had a dominant negative effect on infected by the tungro viruses and also harbor the
yield by reducing 1000-grain weight and percent tungro vectors. The results further indicated that
filled grains. The effect was greater when panicles single infection of RTSV is predominant in the
were inoculated earlier. Increasing levels of other field even in volunteer plants. These plants may
pests in general reduced yields by reducing either serve as direct sources of inoculum and tungro
1000-grain weight, and/or percent filled grains, vectors for the succeeding crop especially in
number of panicles per area, and number of grains asynchronous fields.
per panicle, depending on the pest species and the
pest combination. Effects were more pronounced
if high levels of multiple pests coincided and ANALYSIS OF RESISTANCE TO RICE
especially if they occurred in combination with VIRUSES USING THE IRRI RICE VIRUSES
early panicle blast. Among insect pests, stem DATA BASE. R.C. Cabunagan, H. Koganezawa,
borers were most prevalent. Pest levels were C.A. Carpio, and M.C. Van den Berg. IRRI, Los
generally low, except for panicle blast. Further Baiios, Laguna.
data analysis will center on regression techniques
64 Philipp. Phytopathol. 1992. Vol. 28: 56-68
A Rice Viruses Data Base was developed at NCP thus obtained reacted strongly with purified
A Rice Viruses Data Base was developed at
IRR. The new system organizes information on NCP and infected plants in indirect ELISA. No
IRRI. The new system organizes information on
resistance to rice tungro disease (RTD), rice ragged reaction was obtained with purified RGSV and sap
stunt viruses (RRSV), and rice grassy stunt virus from healthy rice plants. NCP was not detected in
(RGSV). The system provides researchers with insects by DAS-ELISA. Western blotting also
access to current information on rice accessions could detect NCP in extracts of infected plants but
stored in the International Rice Germplasm Center not in insects. These results are consistent with
(IRGC) and evaluated for virus resistance. that reported for maize stripe virus.
Analysis of updated data revealed that for
RTD, 15,795 accessions or 20.5% of the total
IRGC collections have been tested in terms of OCCURRENCE OF RICE SOILS SUPPRES-
resistance to tungro infection. Among them, 560. SIVE TO Rhizoctonia solani. L.H. Carandang,
(3.5%) were resistant (less than 30% infection). A.M. Resales and T.W. Mew. IRRI, Los Bafios,
These resistant varieties originated mostly in South Laguna.
Asia. Only 4,473 accessions (5.8%) have been
screened in terms of disease severity after tungro Field testing of bacterial isolates for
inoculation and 112 accessions were resistant biocontrol of rice diseases has shown variability of
(severity score less than 3). For RRSV, 13,759 results. To determine whether such variability was
accessions (17.1%) have been tested and 336 field specific, soil samples were collected from
(2.4%) from Southeast Asia. For RGSV strain 1, forty plots at the IRRI experimental farm and these
8,376 accessions (10.9%) have been tested and 809 were assayed for suppressiveness and conducive-
(9.7%) were resistant. At high rate, accessions ness to the sheath blight pathogen. Soil samples
from the Middle East and Africa were found were air dried and sieved through 2 mm screen and
resistant. then plated on plastic plates. Sclerotial
Result sets direction for future evaluation of germination and mycelial growth of the pathogen
rice accessions stored in tthe IRGC and resistance were evaluated using these samples. To test for
accessions identified can be used as sources of suppressiveness to sheath blight lesion
genes for breeding lines being developed at IRRI development, soil samples were mixed with the
and in national programs. inoculum of Rhizoctonia solani in a ratio of 1:20
(w/w). IR58, a susceptible variety was directly
seeded into this soil. The rice plants were
SEROLOGICAL DETECTION OF NON- evaluated for sheath blight at 40 days after
CAPSID PROTEIN OF RICE GRASSY STUNT showing. Results showed that sheath blight was
VIRUS. G.J. Miranda and H. Koganezawa. well developed in sterilized soil with pathogen
IRRI, Los Bafos, Laguna inoculum at 21 days after sowing. Out of 40 soils
samples from different field plots, 14 were
Rice grassy stunt virus (RGSV)-infected suppressive to sheath blight development whereas 8
plants were found to produce large amount of non- soil samples were conductive (= the level of
capsid protein (NCP) which is common to all disease development was comparable to the check).
tenuiviruses. The suitability of antibody to RGSV- In three consecutive plantings of rice, several soil
NCP for diagnosis of RGSV-infected plants and samples consistently reduced the sheath blight
insects were studied. severity. Different bacteria were isolated from
As antisera prepared against NCP obtained by these soils, some were gram-negative with either
differential pH precipitation and single ultra- yellow or creamy colony forms, and others were
centrifugation reacted with purified RGSV, NCP gram-positive with white colony types. Both these
was further purified by SDS-PAGE. Antisera of two groups of bacteria inhibited the sclerotia
will be further evaluated and seeaborne tungal pamogens.
in relation to sheath blight control.
DETECTION OF PAPAYA RINGSPOT I
HOGENIC BACTERIA ASSOCIA- ANTIGENS BY ELISA. Ana A. Euseb,
RICE. M.T.R. Cerez. B. Cottvn. F. N.B. Baiet. Department of Plant Pathology,
e bacterial pathogens of (iELISA
have been identified. diluted
7 provinces were studied diluted
,growing-on tests and the detl
identification kits (API antigens
ix SA France], BIOLOG papaya
CA], and Fatty acid technique
Newark, Del.]). The conjugal
anti PRSV-coat protein (C
100 and anti-PRSV virio
00 from Taiwan was deve
if papaya ringspot virus
ya from the field as well ii
'ucurbita pepo seedlings
goat anti-rabbit immune
d at 1:8000 and an incul
nic strains and temperature for 30-40
Amnno those effective when the lea
complex groups of dif
Presence of P. glumae cor
differences in i
iffusion test. Symptomatology of each not show consistent differences in
pathogens is being studied. absorbances among the different samples
Absorbances of the different papaya seed
were not significantly different than those
CTERIZATION OF ANTAGONISTIC healthy samples.
ZIA ASSOCIATED WITH RICE. A.M. These results indicate that a
M.T. Cerez and T.W. Mew. IRRI, Los serologically related to PRSV is infecting
aguna. in the Philippines.
'erent kinds of nonpathogenic bacteria
ated from seeds and tested for inhibition PRELIMINARY SURVEY, IDENTIFIC,
elial growth of Rhizoctonia solani, AND BIOASSAY OF PLANTS WITH
moniliforme and Sarocladium oryzae. CIDE POTENTIAL IN MT. PANGASi
55 isolates tested, 188,36 and 78 isolates L.M. Noriel, E.A. Vasquez, C.V. Ranche:
the growth of the three pathogens, Sopsop and F.M.Y. Duatin. Department
ely. A rapid test for chitinase production Protection, ViSCA, Baybay, Leyte.
ited for characterization of these isolates.
producers were graded from 0 to 5 scale A preliminary survey and identifica
,6 ,D. Phytopathol. 1993, Vol. 28:
ILUT -LUmlC W0I0 lllllllWJ U0UIaJ3U oIAI raoll vaUO 1-uvgallna. w S uaaus, -!Musa3.
:inds of test organisms.
Eighteen species of plants belonging to nine The rice tungro viruses, rice tungro
ilant families were identified during the survey. bacilliform virus (RTBV) and rice tungro spherical
The extracts of Mikania cordata, Cassia alata virus (RTSV) were detected in leaf tissues of
nd Dioscorea hispida caused greater mycelial tungro infected rice, Taichung Native 1, using the
;rowth inhibition on fungal pathogens. indirect method of fluorescent antibody (Fab)
lyricularia oryzae was the most sensitive while staining technique.
'clerotium rolfsii was the least sensitive to the Viral IgG was applied at either 5, 10 or 20
xtracts. ug/ml. Goat antirabbit IgG-fluorescent isothio-
On the other hand, all plant extracts used did cyanate (GAR-FITC) conjugate was used at the
ot show contact and stomach toxicity against concentration of 1/40 dulution. Specific
weet potato weevil. All extracts however, fluorescence was observed in the phloem cells and
ossessed repellant activity, xylem parenchyma cells of leaf tissues from plants
infected with either both RTBV and RTSV or
RTBV alone. Strongest fluorescence was observed
IIOLOGICAL CONTROL OF Rhizoctonia at 10 and 20 ug/ml RTBV-IgG. Sections from
olani KUHN BY FUNGAL ANTAGONIST plants infected with either both RTBV and RTSV
LNF-777. Esperanza G. Celino-Geminde, P.M. or RTSV alone using RTSV-IgG showed
[alos, and Erlinda S. Paterno. Bicol Experiment fluorescence at 20 ug/ml IgG. No fluorescence
station, DA, Pili, Camarines Sur. was observed in the control samples from healthy
and unstained infected tissues.
Out of 7,516 microbial colonies examined in This study confirms results of localization
rowded-plate cultures, 189 prospective antagonists studies of tungro viruses under the electron
'ere isolated and cultured. One of the antogonists microscope. RTBV is located both in the xylem
elected that indicated exceptionally strong and phloem tissue while, RTSV is located in the
ihibitory effect against Rhizoctoni solani Kuhn phloem tissue only.
'as a fungus, ANF-777. Presumptive tests on the The Fab staining is useful technique in the
active substance produced by ANF-777 showed direct observation of the antigen-antibody reaction
lear zones of inhibition against the assay plate in host tissue. It is simple, rapid and sensitive.
rganism, Aspergillus niger.
The antibiotic in the brew was readily
extracted by benzene, butanol, ethyl acetate, and PARAFILM MEMBRANE FOR SERO-ASSAY
iethyl ether. Thin layer chromatography of the OF RICE VIRUSES. E.R. Tiongco, Z.M.
antibiotic gave an RI value of 0.94 and a distinct Flores, H. Koganezawa, and P.S. Teng. IRRI, Los
ihibition zone of 26 mm diameter against A. Bafios, Laguna.
-n iiaIu Iai lLagUllatL au dll n. UL(tftl scCIII
raceable to the production of antibiotic by the
ungal antagonist ANF-777.
ELECTIONN OF TUNGRO VIRUSES IN
EAF TISSUES BY FLUORESCENT
-Luvr-tIu -v u--mV 11^& tulirpu umaoniuiuxu vilua
(RTBV), rice tungro spherical virus (RTSV), rice
grassy stunt virus (RGSV), and rice.ragged stunt
:irus (RRSV) in rice plants and RGSV and RRSV
in the planthopper vector, Nilaparvata lugens. The
parafilm membrane was used as solid phase instead
of microtitre plate. Imprints were marked on the
parafilm membrane by pressing a rod of 2 mm
diameter. Ten to fifteen pl of reagent are deposits
on the imprint. The procedure followed the sat
principle of DAS-ELISA. After coating with vii
antibody, sample and conjugate (alkali
phosphatase-labeled antigen-specific antibodies
were applied simultaneously. Nitroblue tetrazoliu
and 5-bromo-r-chloro-3-indolephosphate we
used as substrate. All procedures were done
room temperature and the membranes were kept
moist chamber to prevent from drying. A positi
result was indicated by the appearance of purp
color visible to the naked eye within 10-30 m
after the addition of substrate. The techniqi
detected viral antigen in 100 times dilution
crude sap of the plarit and insect materials for .
the viruses tested. Using this technique, testily
cost was considerably reduced and the time
assay shortened by 4 hr making it a soui
alternative for a qualitative assay of rice viruses.
MODIFIED TECHNIQUE OF ISOLATION
BACTERIA ANTAGONISTIC TO RIC
SHEATH BLIGHT ORGANISM (Rhizocton
solani Kuhn). D.L. Adorada, T.U. Dalisay, A.'
Plete, G.A. Peralta, A.M. Sinohin and D.B. Lapi
PhilRice-UPLB, College, Laguna
A modified technique of isolating bactei
antagonistic to rice sheath blight organism
(Rhizoctonia solani Kuhn) was developed. T
technique which combined two standard pla
pathological methods, the dilution plate meth,
and dual culture test, in only one set-up is rapi
cost-saving, and effective.