Front Cover
 Component analysis of uredial infection...
 Histopathology of resistant and...
 Comparative effectiveness of chicken...
 Effect of rice-tomato cropping...
 Philippine seed board recommends...
 Stem rot of salago (Wikstroemia...
 Phytopathological Note: Incidence...
 Abstracts of papers presented during...
 Information for contributors

Title: Journal of Tropical Plant Pathology
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00090520/00003
 Material Information
Title: Journal of Tropical Plant Pathology
Series Title: Journal of Tropical Plant Pathology
Physical Description: Serial
Language: English
Creator: Philippine Phytopathological Society, Inc.
Publisher: Philippine Phytopathological Society
Place of Publication: Philippines
Publication Date: 1994
 Record Information
Bibliographic ID: UF00090520
Volume ID: VID00003
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 1624346
electronic_oclc - 54382605
issn - 0115-0804

Table of Contents
    Front Cover
        Front Cover 1
        Front Cover 2
    Component analysis of uredial infection cycle of peanut rust on peanut cultivars
        Page 63
        Page 64
        Page 65
        Page 66
        Page 67
        Page 68
        Page 69
        Page 70
        Page 71
        Page 72
        Page 73
    Histopathology of resistant and susceptible sweet potato cultivars infected with root-knot nematode (meloidogyne incognita)
        Page 74
        Page 75
        Page 76
        Page 77
        Page 78
        Page 79
        Page 80
    Comparative effectiveness of chicken dung, bioact, urea and phenamiphos in controlling nematodes under pot and laboratory conditions
        Page 81
        Page 82
        Page 83
        Page 84
        Page 85
        Page 86
        Page 87
        Page 88
        Page 89
        Page 90
        Page 91
        Page 92
    Effect of rice-tomato cropping patterns and flooding on the survival of pseudomonas solanacearum E.F. Smith
        Page 93
        Page 94
        Page 95
        Page 96
        Page 97
        Page 98
        Page 99
    Philippine seed board recommends high yielding and downy mildew resistant corn varieties developed at USM, Kabacan, Cotabato
        Page 100
        Page 101
        Page 102
        Page 103
        Page 104
        Page 105
        Page 106
        Page 107
        Page 108
        Page 109
        Page 110
    Stem rot of salago (Wikstroemia lanceolata L.). II. survival, host range and control of botryodiplodia theobromae pat
        Page 111
        Page 112
        Page 113
        Page 114
        Page 115
        Page 116
        Page 117
    Phytopathological Note: Incidence of two new fungal leaf diseases of Kalachuchi (Plumeria acuminata AIT.)
        Page 118
        Page 119
        Page 120
        Page 121
    Abstracts of papers presented during the 25th annual convention of the pest management council of the Philippines, Cagayan de Oro City, May 3-6, 1994
        Page 122
        Page 123
        Page 124
        Page 125
        Page 126
        Page 127
        Page 128
        Page 129
        Page 130
        Page 131
        Page 132
        Page 133
        Page 134
        Page 135
        Page 136
        Page 137
        Page 138
        Page 139
        Page 140
        Page 141
        Page 142
        Page 143
        Page 144
    Information for contributors
        Page 145
        Page 146
Full Text

Official Publication of the Philippine Phytopathologiccal Society, Inc.


Business Manager
Board Member
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Immediate Past President




Associate Editor
Associate Editor

Subscriptions: Communications should be addressed to the TREASURER, P.P.S. c/o Department of
Plant Pathology, UPLB, College, Laguna 4031. Philippine Phytopathology, published semi-annually, is the
official publication of the Philippine Phytopathological Society, Inc. It is sent free to members in good
standing and Sustaining Associates. For others, it is P50.00 per copy (domestic) and $ 150.00 per copy
elsewhere, postage free and payable in advance. Membership in the Philippine Phytopatholoical Society
Inc.: Information regarding membership will be supplied by the Secretary upon request. ae Charge:
The Editorial Board reserves the right to charge some authors a modest amount for each published page
commensurate upon the payment capability of their research projects or supporting institutions.
Advertisements: Rates may be secured from the Business Manager. No endorsement of any statement
of claims made in advertisements is assumed by this Journal or by the Philippine Phytopathological
Society, Inc.

Philipp. Phytopathol. 1994, Vol. 30(2):63-73



Associate Professor and University Research Associate, respectively, University
of the Philippines at Los Bafios (UPLB), College, Laguna, Philippines.

Key words: Components analysis, cohort life table, epidemiology, peanut, peanut
rust, reproductive table


Cohorts of uredospores of Puccinia arachidis were
allowed to undergo infection process on the leaves of three
peanut cultivars, namely, BPI-P9, UPL-Pn2 and UPL-Pn4.
Cohort life and reproductive table statistics were used as
bases for comparisons on the interactions of P. arachidis and
peanut cultivars. High mortality of infection units was
observed in all cultivars during the early stages of infection
cycle. There were significant differences in the proportion of
infection units reaching germination, germtube formation and
appressorium formation in the three cultivars. The difference
in the survival rates of the infection units was translated into
infection efficiencies of 5, 4 and 3% on BPI-P9, UPL-Pn2 and
UPL-Pn4, respectively.

Reproductivity of P. arachidis varied according to
cultivars. The fungus produced abundant uredospores per
pustule on BPI-P9 and UPL-Pn2 but the reproductive period
was relatively shorter. There was a 2-fold reduction of
sporulation in UPL-Pn4, but the duration of sporulation was
longer. Any successful uredospore from the original cohort
had a chance to produce 262, 153 and 54 effective
uredospores per pustule on BPI-P9, UPL-Pn2, and UPL-Pn4,
respectively. The maximum relative growth rate or the
maximum infection rate possible under the conditions of this
experiment were 0.40, 0.36 and 0.30 unit/day on BPI-P9,
UPL-Pn2 and UPL-Pn4, respectively. The mean generation
time was estimated at 14 days and it did not vary among


Peanut (Arachis hypogaea L.) is a cantly because of many production
very important crop and its production constraints including the occurrence of
has recently received strong emphasis destructive foliar diseases.
in the Philippines. Despite production
supports, hectarage and quantity of Peanut rust, caused by Puccinia
production did not increase signifi- arachidis Spegazzini is regarded as a

major problem as it can render
complete crop failure under high
epidemic situations. The disease is
commonly managed by the use of
fungicides and resistant cultivars. At
present, several commercial cultivars
have been recommended against the
disease. However, there is lack of
understanding on how they can affect
the population of peanut rust
pathogen. Such understanding can
give insight into the utilization of
cultivars for efficient disease

Fortunately, ecology has provided
powerful analytical procedures for
better understanding of population
attributes at various situations which
could be applied to plant diseases. For
instance, a population can be arranged
in an orderly system of statistics called
life table which can be extended to a
reproductive table.

Life table is a condensed tabulation
of the essential information pertaining
to the schedule of mortality for a
known cohort of individuals (Harcourt,
1969). Life tables were initially used
for non-human populations in the study
of organisms such as Drosophila
melanogaster (Pearl and Parker, 1921)
and Tribolium confusum (Pearl et al.,
1941). Deevey (1947) was the first to
apply the technique to growing
populations in nature and Morris and
Miller (1954) presented the first
detailed example of a life table for
natural population of an insect. The
technique has been used extensively in
wildlife management and in the field of
insurance to ascertain the probability
of death (Harcourt, 1969).

Since life table operates on the
assumption that age distribution of the
population is stable, it is quite difficult
to use in the study of pathogen
populations. However, another type of
life table known as age-specific or
cohort life table may be used. Zadoks
and Schein (1979) discussed the
application of the technique in the

Philipp. Phytopathol. 1994, Vol. 30(2):63-73

study of population dynamics of
pathogens. In a cohort life table, a
population of the same age is followed
through its development and deaths or
births of infection units are noted as
the population reaches some
recognizable states of infection
process. Cohort life table contains vital
statistics such as mortality, survival
and life expectancy of infection units
as they reach various states of
infection process. It can be extended
into a reproductive table which
contains statistics which account for
reproduction such as number of
offspring per individual, net
reproduction rate, generation time and
relative growth rate. These, including
cohort life table statistics, could serve
as bases for epidemiological com-
parisons thus giving some ideas on
how similar populations of the same
pathogen will .be more or less
successful at various situations.

In this study, we used cohort life
and reproductivity table statistics to
compare the interactions of
P. arachidis and three peanut cultivars.


Test Plants

Three varieties of peanut with
different reactions to peanut rust were
used. These were BPI-P9 (susceptible),
UPL-Pn2 (moderately susceptible) and
UPL-Pn4 (resistant). All test plants
were grown in sterilized soil placed in
15-cm pots. Recommended cultural
practices were strictly followed to give
favorable conditions for plant growth
and development.

Inoculum and Inoculation of
Test Plants

Peanut plants showing symptoms
of leaf rust were collected from the
field. Dried uredospores were extracted
from infected plants using a spore
collector attached to a vacuum pump.

Philipp. Phytopathol. 1994, Vol. 30(2):63-73

These were inoculated to test plants
late in the afternoon with the aid of
improvised plastic settling tower.
Inoculation was done by violently
releasing approximately five grams of
uredospores on top of the settling
tower. The settling tower allowed an
even distribution of uredospore
deposition on the leaves and also
served as the incubation chamber for
inoculated plants. The test plants were
removed from the settling tower after
24 hr and returned to the screenhouse
for disease development.

Cohort Life Table

tubes, appressoria and pustules per
0.25 cm' of leaf surface was deter-
mined. The measurements of infection
units were done in three replicates.

Life table statistics. The life
table statistics of peanut rust were
determined in each variety (Table 1).
These were the mortality (q,) and
survival (I-q,) ratios, proportion of
surviving infection units (I,).
Survivorship curves of P. arachidis
were established in the three test

Reproductive Table

States of peanut rust infection.
Uredospores of P. arachidis on the
leaves of three peanut cultivars were
monitored as they undergo infection
process. The development was
observed according to the different
states of infection cycle that were
easily recognizable by light mic-
roscopy. These were ungerminated
uredospores, germinated uredospores,
germtube formation, appressorium
formation and pustule formation
(Fig. 1). At desired time intervals, the
densities of infection units passing
through the identified states were
assessed. These were the total
uredospore density (TUD), germinated
uredospore density (GUD), germtube
density (GTD), appressorium density
(APD), pustule density (PUD) and
surviving pustule density (SPD)
[Table 1].

Measurement of infection units.
After inoculation, leaflets of each
variety were detached randomly at
different time intervals. Leaf samples
were fixed in formalin-aceto-alcohol
combination (FAA) for 24 hr,
decolorized in Carnoy's solution for 24
to 48 hr, and stained in lactophenol
cotton blue for 24 hr. The stained leaf
samples were carefully cut into pieces
and mounted on microscopic slides.
The number of ungerminated uredo-
spores, germinated uredospores, germ-

Uredospore production. Uredospore
production on three peanut varieties
was determined 10 days after ino-
culation. Leaflets with known number
of rust pustules were tagged and
uredospores were collected using
spore collector attached to a vacuum
pump. Uredospores were suspended in
10 ml distilled water with a drop of
Tween 40 to insure even dispersion of
uredospores. Uredospore density was
determined using a hemacytometer
(Tuite, 1969). The measurements of
uredospore production were taken at
2-day intervals until pustules have
stopped sporulation, and were done in
three replicates.

Reproductive table statistics. The
reproductive table statistics of
P. arachidis, namely, the number of
uredospores per pustule per unit of
time (mt), the proportion of surviving
uredospsores (It), number of age-
specific surviving uredospores (Itmt)
and the product of time (t) and Itmt
(Table 1) were determined on three
peanut varieties. Using the above
statistics, reproductive tables and
reproductive curves were constructed.
The net reproduction per generation
per infection unit (Ro), mean
generation time (Tg) and maximum
relative growth rate (rmax) were also
determined using the formula by
Zadoks and Schein (1979).

Philipp. Phytopathol. 1994, Vol. 30(2):63-73

Fig 1. Five states

of infection cycle of Puccinia arachidis that are easily
by light microscopy: A, uredospores; B, germinating
C, germtube formation; D, appressorium formation and E,

pustule formation.


Cohort Life Table of P. arachidis

The fate of initial cohorts of
uredospores deposited on the leaves of
three peanut cultivars is presented in
Table 2. The densities of germinated
uredospores, germtubes, appressoria
and rust pustules were significantly
higher in BPI-P9 and UPL-Pn2
compared with UPL-Pn4 (Table 3). All
pustules were no longer infective 26
days after inoculation.

.Survival of infection units. Cohorts
of uredospores sustained low survival
rates during the early stages and
higher survival rates during the later
stages of infection process on the
three peanut cultivars (Table 4 and Fig.
2). The survival rates differed
significantly among the three cultivars
and the differences were more obvious
on the 1st to 3rd day of infection. BPI-
P9 showed the highest proportion of

surviving infection units followed by
UPL-Pn2. Infection units sustained low
survival rates in UPL-Pn4.

The survival ratios, expressed as
the ratio between the number of
infection units and the number of
surviving units that undergo the next
state of infection process, differed
according to the different peanut
cultivars (Table 5). Results suggest
that all cultivars exhibited blocking
effects on infection during uredospore
germination and appressorium
formation with more pronounced effect
in UPL-Pn4. Higher survival was
observed from appressorium to pustule
formation. The infection efficiency,
expressed as the ratio of the number
of uredospores and the number of
pustules did not vary significantly
among the cultivars.

Life expectancy. The calculated life
expectancy of infection units of
P. arachidis varied according to cultivar


Philipp. Phytopathol. 1994, Vol. 30(2):63-73

Table 1. List of variables used in
Puccinia arachidis.

the construction of life and reproductive tables of


Total Uredospore

Germinated Uredo-
spore Density

Germtube Density


Pustule Density

Surviving Pustule

Mortality Ratio








Survival Ratio

Life Expectancy

Age-specific Repro-
duction Rate

Proportion of

Net Reproduction

Generation Time

Maximum relative
Growth Rate







Number of uredospore deposited
per unit leaf area

Number of germinating uredo-
spores per unit leaf area

Number of germtubes produced
per unit leaf area

Number of appressoria produced
per unit leaf area

Number of pustules formed per
unit leaf area

Sporulating or uredospore produ-
cing pustules per unit leaf area

Proportion of infection units dying
in each state of infection process

Proportion of infection units
surviving in state of infection

The expected time for infection
units to live in each state
of infection

The number of uredospores per
pustule of age t

Proportion of survivors at
any t

The net reproduction rate per
infection unit

Length of disease cycle

The maximum relative growth rate
which sets an upper limit to the
rate of disease development

of uredospores and the number of
pustules did not vary significantly
among the cultivars.

Life expectancy. The calculated life
expectancy of infection units of
P. arachidis varied according to cultivar
















Table 2. Cohort life table of Puccinia a

Philipp. Phytopathol. 1994, Vol. 30(2):63-73

,rachidis on the leaves of three peanut

(day) STATE2 (no./0.25 cm2) (qt) (I-qt) (It) (et)

BPI-P9 0 TUD 24.26 0.57 0.43 1.00 1.9
1 GUD 10.47 0.47 0.53 0.43 2.7
2 GTD 5.50 0.70 0.30 0.23 3.7
3 APD 1.67 0.26 0.74 0.07 10.0
9 PUD 1.23 1.00 0.00 0.05 6.8
26 SPD 0

UPL-Pn2 0 TUD 23.80 0.70 0.30 1.00 1.5
1 GUD 7.07 0.52 0.48 0.30 3.0
2 GTD 3.37 0.67 0.33 0.14 4.8
3 APD 1.10 0.15 0.85 0.05 11.6
9 PUD 0.93 1.00 0.00 0.04 8.5
26 SPD 0

UPL-Pn4 0 TUD 24.07 0.82 0.18 1.00 1.3
1 GUD 4.23 0.40 0.60 0.18 4.1
2 GTD 2.53 0.74 0.26 0.11 5.4
3 ARD 0.62 0.06 0.94 0.03 12.3
9 PUD 0.63 1.00 0.00 0.03 11.3
26 SPD 0

2Average of three replicates.
TUD = total uredospore density; GUD = germinated uredospore density; GTD = germtube density;
APD = appressorium density; PUD = pustule density and SPD = surviving pustule density.
Proportion of survivors at any infection state; it is simply calculated as the number of survivor at any
state divided by the initial total uredospore density.

Table 3. Number of infection units of Puccinia arachidis at different age intervals
and state of infection process on three peanut cultivars.

(days) BPI-P9 UPL-Pn2 UPL-Pn4

0 TUD 24.26 a 23.80 a 24.07 a
1 GUD 10.47 a 7.07 ab 4.23b
2 GTD 5.50 a 3.37 ab 2.53 b
3 APD 1.67 a 1.10 a 0.67 b
9 PUD 1.23 a 0.93 a 0.63 b
26 SPD

Means of three replicates; to compare means within rows (among cultivars) means having common letter
are not significantly different using LSD0.

Philipp. Phytopathol. 1994, Vol. 30(2):63-73

Table 4. Proportion of surviving infection units of Puccinia arachidis at any infection
state in the leaves of three peanut cultivars.

(days) BPI-P9 UPL-Pn2 UPL-Pn4

0 TUD 1.00 a 1.00 a 1.00 a
1 GUD 0.43 a 0.30 a .0.18 b
2 GTD 0.23 a 0.14 ab 0.11 b
3 APD 0.07 a 0.05 a 0.03 a
9 PUD 0.05 a 0.04 a 0.03 a
26 SPD 0. 0 0

1Means of three replicates; to compare means within rows (among cultivars) means having common
letter are not significantly different using LSDO.05.

Table 5. Survival ratio of infection units
peanut cultivars.

of Puccinia arachidis on the leaves of three


Germinated/Total Uredospore 0.43 a 0.30 a 0.18 b

Germtube/Germinated 0.53 a 0.48 a 0.60 a

Appressorium/Germtube 0.30 a 0.33 a 0.26 a

Pustule/Appressorium 0.74 a 0.85 ab 0.94 b

Pustule/Total Uredospore
(Infection Efficiency) 0.05 a 0.04 a 0.03 a

1Means of three replicates; to compare means within rows (among cultivars), means having common
letter are not significantly different using LSDO.05.

Table 6. Estimated life expectancy of infection units of Puccinia arachidis at
different state of infection process on three peanut cultivars.

(days) BPI-P9 UPL-Pn2 UPL-Pn4

0 TUD 1.9 1.5 1.3
1 GUD 2.7 3.0 4.1
2 GTD 3.7 4.8 5.4
3 APD 10.0 11.6 12.3
9 PUD 6.8 8.5 11.3
26 SPD

Means of three replicates; to compare means within rows (among cultivars) means having common
letter are not significantly different using LSDO.05.

and state of infection (Table 6). Data
showed that uredospores undergoing
early stages in the infection process
expect to live shorter than those
infection units undergoing the later
stages of infection process. For
instance, germinated uredospores can
expect to live from 1.3 to 1.9 days
while germtubes transformed into
appressoria can expect to live within
10 to 12 days. Pustule from UPL-Pn4
tended to live longer compared to
pustules from susceptible varieties.

On the basis of life table statistics,
results indicate that high mortality of
infection units occurred during germi-
nation and appressorium formation.
This suggests that germination and
appressorium formation are the most
vulnerable stages in the infection cycle
of P. arachidis that could be easily
affected by the host or changes in the
environment. Mortality of infection
units was more pronounced in UPL-
Pn4. This also indicates that the
observed higher degree of resistance
conferred by UPL-Pn4 compared with
BPI-P9 and UPL-Pn2 may be partly
attributed to its ability to suppress
spore germination and appressorium
formation. The exact mechanism of
suppression is not certain. However,
Foudin and Macko (1974) and Cook
(1980) reported that uredospores of P.
arachidis were sensitive to methyl cis-
3, 4-dimethoxy cinnamate, an inhibitor
of spore germination. It is possible that
UPL-Pn4 possessed some biochemical
substances that inhibit spore

Life expectancy statistics con-
formed with mortality or survival statis-
tics. Infection units passing through
the early stages of infection cycle can
expect to live shorter than those of the
later stages. Once P. arachidis
produced appressoria, it is expected to
live longer and to produce pustules
with higher probability.

Philipp. Phytopathol. 1994, Vol. 30(2):63-73

The infection efficiency was lowest
on UPL-Pn4, but the difference was
not statistically significant. The high
mortality of infection units in UPL-Pn4
at early stage of infection process
could be compensated by the higher
survival and longer life expectancy of
infection units during the later stages.

Reproductivity Table of P. arachidis

The reproductivity table of
P. arachidis on three peanut cultivars
was constructed on the basis of the
assessed age-specific reproductivity
rates (Table 7). A graph of the
cumulative age-specific reproductivity
rates over time clearly showed the
difference in the magnitude of
sporulation capacity of P. arachidis on
the three cultivars (Fig. 3). The fungus
produced abundant uredospores on
BPI-P9 and UPL-Pn2 while there was a
2-fold reduction of sporulation on UPL-
Pn4. The reduced sporulation can be
attributed to the reduced size of rust
pustules produced on UPL-Pn4.
Although the fungus produced bigger
pustules and abundant uredospores on
BPI-P9 and UPL-Pn2, the period of
reproduction was relatively shorter.

The reproductivity statistics were
calculated and summarized in
Table 8. Calculations of the net
reproduction rates (Ro) of P. arachidis
on the three peanut cultivars indicated-
that a single uredospore had a
chance to produce 262, 153 and 64
effective uredospores per pustule on
BPI-P9, UPL-Pn2 and UPL-Pn4,
respectively. Consequently, the
maximum relative growth rate (rm.x)
was estimated as 0.40, 0.36 and 0.30
uredospore per original uredospore per
day for BPI-P9, UPL-Pn2 and UPL-Pn4,
respectively. The mean generation time
or the length of infection cycle was
about 14 days and it did not vary
among cultivars.

Philipp. Phytopathol. 1994, Vol. 30(2):63-73

Table 7. Reproductivity table of Puccinia arachidis in the

leaves of three peanut

(t) (mt) AGE (It) mt and It t and mt.It

BPI-P9 10 1620 Q.047 76.14 761.40
12 540 0.041 22.14 265.68
14 1645 0.035 57.65 807.10
16 1926 0.029 55.85 893.60
18 1120 0.023 25.76 463.68
20 1294 0.017 22.00 440.00
22 193 0.011 2.12 46.64
24 0 0.005 0 0
26 0 0 0 0

UPL-Pn2 10 1187 0.038 45.11 451.10
12 600 0.033 19.80 237.60
14 1166 0.028 32.65 457.10
16 960 0.023 22.08 353.28
18 660 0.018 11.88 213.84
20 1347 0.013 17.51 350.20
22 473 0.008 3.78 83.16
24 0 0.003 0 0
26 0 0 0 0

UPL-Pn4 10 640 0.028 17.92 179.20
12 440 0.024 10.56 126.72
14 533 0.020 10.66 149.24
16 720 0.016 11.52 184.32
18 647 0.012 7.56 139.68
20 287 0.008 2.30 46.00
22 840 0.004 3.36 73.92
24 100 0.002 0.20 4.80
26 0 0 0 0

Table 8. Reproductivity statistics of Puccinia arachidis on three peanut cultivars.


Net reproduction rate,
Ro (No./pustule) 262 153 64

Generation time. Tg
(in days) 14 14 14

Maximum relative growth
rate, rmax (unit per day) 0.40 0.36 0.30

Philipp. Phytopathol. 1994, Vol. 30(2):63-73

Fig. 2. Survivorship curves of Puccinia arachidis on the leaves of the three peanut cultivars.

0 2 4 6

8 10 I 14 16
Age Intervals in Days

18 20 22 24 26


Fig. 3. Reproductivity curves of Pucchiia arachidis on the leaves of three peanut cultivars.


I 8-


a 4-



--0 BPI-P9
--e UPL- Pn2
0--0 UPL- Pn4


Philipp. Phytopathol. 1994, Vol. 30(2):63-73

The cohort life table described
previously does not account for repro-
duction which is regarded as a major
driving force of population growth.
The reproductivity table clearly indica-
ted that the difference in resistance
conferred by the cultivars against
P. arachidis can be attributed to the
suppression of sporulation. The calcu-
lated Ro of P. arachidis on UPL-Pn4
was about 4-fold reduction in the
number of offspring (uredospores)
per original uredospores in a single
generation compared with susceptible
cultivar (BPI-P9). The reduction in Ro
is related to the reduction in r(max)
that is analogous to apparent infection
rate (Vanderplank, 1963). The r(max)
sets an upper limit to the rate of
disease development under the condi-
tions of the experiment. Under field
epidemic situation, however, the
apparent infection rate of peanut rust
was about 0.171 unit/day (calculated
from unpublished data). The estimated

r(max) in the resistant cultivar is still
higher than that found in the field
because r(max) was attained with the
unrealistic assumption that all newly
produced spores would actually arrive
at the infectible tissues. The fact that
r(max) was substantially reduced in
UPL-Pn4, the difference in resistance
could also be attributed to the reduc-
tion in the rate of disease develop-
ment. The length of infection cycle
(Tg) did not vary among the cultivars
suggesting that the resistance of UPL-
Pn4 against P. arachidis is not related
with Tg.

On the basis of the life and repro-
ductivity table statistics, it is conclu-
ded that the degree of resistance
conferred by UPL-Pn4 against
P. arachidis can be attributed to its
ability to suppress uredospore germi-
nation, appressorium formation,
uredospore production and conse-
quently reduction in the rate of
epidemic development.


COOK, M. 1980. Host-parasite relations in
uredial infections of peanut by Puccinia
arachidis. Phytopathology 70: 822-

DEEVEY, E.S., JR. 1947. Life tables for
natural population of animals. Quart.
Rev. Biol. 22:283-314.

FOUDIN, A.S. and V. MACKO. 1974.
Identification of the self-inhibitor and
some germination characteristics of
peanut rust .uredospores. Phyto-
pathology 25: 715-725.

HARCOURT, D.G. 1969. The development
and use of life tables in the study of
natural insect populations. Ann. Rev.
Entomol. 14: 175-196.

MORRIS, R. and C.A. MILLER. 1954. The
development of life tables for the
spruce budworm. Can. J. Zool. 32:

PEARL, R. and S.L. PARKER. .1921.
Experimental studies on the duration of
life: An introductory discussion of the
duration of life in Drosophila. Am.
Naturalist. 5:481 509.

PEARL, R., T. PARK and J.R. MINER. 1941.
Experimental studies on the duration of
life:Life tables for the flour beetle
Tribolium confusum Dural. Am.
Naturalist. 75: 5-19.

TUITE, J. 1969. Plant pathological
methods: fungi and bacteria. Burgess
Publ. Co., Minneapolis, Minnesota.
239 pp.

VANDERPLANK, J.E. 1963. Plant diseases:
Epidemics and control. Academic Press,
New York. 349 pp.

ZADOKS, J.C. and R.D. SCHEIN.1979.
Epidemiology and plant disease
management. Oxford University Press,
New York. 521 pp.

Philipp. Phytopathol. 1994, Vol. 30(2):74-80


R.M. Gapasin

Professor, Department of Plant Protection, Visayas State College of Agriculture
(ViSCA), Baybay, Leyte, Philippines.

Key words: Giant cells, histopathology, Meloidogyne incognita, sweet potato.


Histopathology of galled roots in susceptible sweet
potato cv. Binicol showed the formation of multinucleated
and thick-walled giant cells. Parenchyma cells around giant
cells exhibited hypertrophy and hyperplasia, and cytoplasm
within giant cells became granulated. Displacement or
abnormal growth of vascular elements was evident due to the
pressure exerted by the growth of the nematode and
development of giant cells. In the resistant cultivar (cv.
Jasper), hypersensitivity, cell necroses, formation of
"wound" periderm and "aborted" giant cells were evident.
Where successful invasions occurred, smaller and fewer giant
cells were observed at the sites of infection.


The root-knot nematode,
Meloidogyne incognita, is one of the
most important pests of sweet potato.
It causes galling on the feeder roots,
roughening and frequent cracking of
tubers and generalized decay of the
entire fibrous root system, thus
reducing the quantity and quality of
tuber yields.

Studies on the reactions of sweet
potato to the root-knot nematode have
been reported. According to Weimer
and Harter (1925) sweet potato
cultivars resistant to M. incognita
showed only occasional knots on the
roots and few blister-like areas on
fleshy roots. Likewise, Dean and
Struble (1953) reported that
nematodes entering roots of resistant

sweet potato (cv. Orlis, Oklahoma 46,
Oklahoma 29) produced necroses of
host tissues several days after
infection which were not observed in
susceptible roots (cv. Algold). Other
workers confirmed that reactions of
sweet potato cultivars ranged from
very susceptible to highly resistant
(Cordner et al., 1951; Kushman and
Machmer, 1947; Giamalva et al.,
1960). Gapasin (1984) screened 52
sweet potato cultivars for their
resistance to M. incognita and found
that fewer nematodes penetrated the
resistant cultivars, Jasper, Jewel and
W-86 compared to the susceptible
cultivars, Binicol and UPR.

Histopathological studies on sweet
potato infected with root-knot

Philipp. Phytopathol. 1994, Vol. 30(2):74-80

nematode are very limited. In the cv.
Porto Rico, nematode feeding
stimulated the formation of several
atypical tissues, giant cells, "abnormal"
xylem, hyperplastic parenchyma and
cork (Krusberg and Nielsen, 1958). So
far, no reports on histological changes
occurring on resistant varieties of
sweet potato have been made.
However, in resistant soybeans (cv.
"Peking"), many syncytia degenerated
within five days after inoculation and
were associated with dead
second-stage larvae. Likewise, the
mechanism of resistance of some
potato clones to the cyst nematode,
Globodera rostochiensis, involved the
vacuolation of the syncytial cytoplasm,
necrosis and enclosure of the
syncytium. However, these were not
exactly the same for all of the resistant

This study was therefore
conducted to compare the
histopathology of resistant and
susceptible sweet potato cultivars to
M. incognita.


The cultivars Binicol (susceptible)
and Jasper (resistant) were planted in
7.5-cm diameter clay pots and
inoculated separately with 200 larvae
of M. incognita. At 21 days after
inoculation, root samples of each
cultivar were washed in tap water.
Galled and ungalled roots were
carefully selected and cut to about 5
mm long. The root samples were
placed separately in vials and fixed
with FPP (formalin-propanol-propionic
acid) for 5 days. The roots were
dehydrated gradually in tertiary butyl
alcohol (TBA) series following the
procedure of Jensen (1962). The
dehydrated roots were embedded in
paraffin and sectioned at 12 um using
a rotary microtome (Spencer


American Optical

The resulting paraffin ribbons
were placed on glass slides with a thin
coating of egg albumin adhesive and
then floated in a few drops of 4%
formalin. The slides were dried on a
slide warmer (40 C) and later kept in
slide boxes.

The sections were stained
following the schedule of Jensen
(1962). After staining, the sections
were mounted in Canada balsam and
air-dried for 24 hours. The slide
mounts were examined under a
microscope and cellular changes
induced by the nematode in resistant
and susceptible cultivars were
compared. Photomicrographs were
taken to show histopathological


Comparative histological studies
were done in both susceptible and
resistant sweet potato cultivars
infected with M. incognita. The
susceptible cultivar (Binicol) formed
multinucleated giant cells around the
head of the nematode. These giant
cells are considered the "nurse" cells
on which the sedentary larvae and
adult females feed (Pate and Gunning,
1972). It is, therefore very important
that these cells be maintained in order
that the nematodes develop normally
and attain maturity. It was further
observed that the nuclei and nucleoli of
these cells were enlarged.
Hypertrophy and hyperplasia also
occurred in the parenchyma cells
surrounding the giant cells. The walls
of these cells became thickened and
cytoplasm were granulated as they
increased in size several days after
infection (Figure 1A, B, C, D). This
observation is in consonance with

other histopathological studies of
root-knot nematode galls in other
plants (Bird, 1961; Christie, 1936;
Crittenden, 1958; Dropkin and Nelson,
1960; Krusberg and Nielsen, 1958).

How the multinucleated giant cells
were formed in the susceptible
cultivars (Binicol) was not ascertained
in this study. In other susceptible
plants, however, this condition has
been attributed to cell wall dissolution
and/or repeated mitosis without
cytokinesis (Paulson and Webster,
1970; Bird, 1961; Dropkin and Nelson,
1960; Owens and Specht, 1964;
Huang and Maggenti, 1969; Jones and
Payne, 1978).

The thickening of the walls of
individual giant cell in the susceptible
cultivars was believed to be a response
of the cells to stimulating substances
seeping between cells (Dropkin and
Nelson, 1960). Hypertrophy and
hyperplasia surrounding nematode
body and giant cells may be responses
of the host to mechanical pressure
exerted by the enlarging nematode or
to lateral movement of growth
substances around the cavity created
by growth of the parasite. The dense
and granulated cytoplasm could also
indicate protein deposition by the
parasite or to rapid synthesis by the
host cells (Owens and Specht, 1964).

The resistant cultivar (Jasper)
produced necrotic cells as a
hypersensitive response to nematode
feeding. "Aborted" or empty giant
cells were also observed. Whenever
successful invasion occurred, fewer
and smaller giant cells were formed
and the invading nematode was
surrounded by "wound" periderm
deposits (Fig. 2A, B, C, D).

The hypersensitive reaction of the
resistant cultivar to nematode infection
in this study was similar to that

Philipp. Phytopathol. 1994, Vol. 30(2):74-80

observed in other resistant crops. The
root-knot nematode, M. incognita,
infecting roots of tomato cv. Hawaii
5229 caused cell death around the
nematode after 24 hr and death of the
nematode occurred within 96 hr (Riggs
and Winstead, 1959). In contrast, the
hypersensitive reaction of flue cured
tobacco resistant to M. incognita acrita
was induced only after the susceptible
response (giant cell formation) had
taken place (Powell, 1962).
Observations of the soybean cyst
nematode, Heterodera glycines, on
resistant soybean indicate that once
migrating larvae become sedentary,
cells around the head become
disorganized and necrotic thus,
preventing giant cell formation.

The presence of aborted giant cells and
necroses in the resistant cultivar
Jasper is in agreement with the
observation of Malo (1960) who
reported that giant cells in resistant
peach cultivar became empty and
eventually replaced by suberin
materials. Yu and Steele (1981) also
reported that in nematode resistant
diploid Beta vulgaris L. line "51501",
the nematodes deteriorated
concomitant with necroses of the
syncytia and dead nematodes
frequently appeared macerated or
flattened and deformed. The formation
of "wound" periderm around the
hypersensitive region in the resistant
cultivars is in agreement with the
findings of Van Gundy and Kirkpatrick
(1964). The deposition of suberin and
formation of wound periderm is a
resistant reaction which was evident in
the cultivar Jasper which is an
important mechanism to limit the
formation of giant cells that provide
nutrients for the nematode.

The hypersensitivity or cell
necrosis in resistant cultivars may be
due to compounds present in the host
which were triggered by the nematode

Philipp. Phytopathol. 1994, Vol. 30(2):74-80

Fig. 1. Anatomical changes occurring in roots of susceptible cultivar Binicol infected
:-4 1-:

phloem (ph). B. Longitudinal section showing a nematode (ne) feeding on
bioi.. H h o e o Cth s t

S(h) on shwn a i
Ph '\ Wt*^ ss^

A0 2 4. ti' r *

*"0 a- *-*--T L4 I
*t,;'^ ;' T, *Li ..

B D -, *-

Fig. 1. Anatomical changes occurring in roots of susceptible cultivar Binicol infected
by Meloidogyne incognita. A. Healthy cross section of the sweet potato
root showing the epidermis (e), cortex (c), endodermis (en), xylem (xy), and
phloem (ph). B. Longitudinal section showing a nematode (ne) feeding on
giant cells (g). Several multinucleated giant cells (nu) and abnormal xylem
(abx) vessels formed as a response to infection. C. Cross section of a galled
root showing hypertrophy (hy) of endodermal and pericycle cells and
hyperplastic parenchyma cells (hp) around giant cells (g). D. Close up view
of a giant cell (g) showing thickened cell wall (tcw), granulated cytoplasm
and multinucleated (nu) giant cells.

Philipp. Phytopathol. 1994, Vol. 30(2):74-80

:L ` 2-

.'' NF~p

Fig. 2. Anatomical changes occurring in roots of resistant cultivar Jasper infected
by Meloidogyne incognita. Cross section (A) and longitudinal section (B) of
roots showing formation of "wound" periderm (pe) and collapsed giant cells
(eg). Hypersensitive reactions (arrows) and necrotic cells surrounding
"aborted" giant cells (eg). Successful invasion of the nematode produces
smaller giant cells in resistant variety Jasper (C and D).

Philipp. Phytopathol. 1994, Vol. 30(2):74-80

enzymes. Giebel et al. (1971) found
that necrotic cells in roots of resistant
potato had high activity of peroxidase,
tyrosinase and B-glucosidase. They
suggested that the peroxidase in the
resistant varieties may play an
important role in the formation of
conditions favoring lignin synthesis in
the necrotic area.

Based on the above findings, the
resistance of sweet potato against M.
incognita could be attributed to the
hypersensitive reaction or death of
cells, fewer and smaller giant cells
produced, and walling-off and or
production of toxic metabolites as a
result of the hypersensitive reaction.
These resistance mechanisms would
kill or delay the development of the
infecting nematode.


BIRD, A.F. 1961. The ultrastructure
and histochemistry of a
nematode-induced giant cells. J.
Biophys. Biochem Cytol. 2:

CHRISTIE, J.R. 1936. The develop-
ment of root-knot nematode
galls. Phytopathology 26: 1-22.

L.S. MORRISON. 1951. Reaction
of sweet potato varieties and
seedlings to root-knot nematodes
(Abstr.). Proc. Assoc., Southern
Agr. Workers 48: 119.

CRITTENDEN, H.W. 1958. Histology
and cytology of susceptible and
resistant soybeans infected with
Meloidogyne incognita acrita.
Phytopathology 48: 461.

DEAN, J.L. and F.B. STRUBLE. 1953.
Resistance and susceptibility to

root-knot nematodes in tomato
and sweet potato. Phytopathology
43: 290.

1960. The histopathology of
root-knot nematode infections in
soybean. Phytopathology 50:

GAPASIN, R.M. 1984. Resistance of
fifty-two sweet potato [Ipomoea
batatas (L.) Lam.] cultivars to
Meloidogyne incognita and M.
javanica. Ann. Trop. Res. 61: 1-9.

T.P. HERNANDEZ. 1960. Reaction
of eight sweet potato selections to
five species of root-knot
nematodes. Phytopathology 50:

1971. Localization of some
enzymes in roots of susceptible
and resistant potatoes infected
with Heterodera rostochiensis.
Nematologica 17: 29-33.

1969. Wall modification in
developing giant cells of Vicia faba
and Cucumis sativus induced by
the root-knot nematode, Meloido-
gyne javanica. Phytopathology
59: 931-937.

JENSEN, W.A. 1962. Botanical
histochemistry. W.H. Freeman and
Co. London. pp. 55-99.

1978. Early stages of nematode-
induced giant cell formation in
roots of Impatiens balsamina. J.
Nematol. 10: 70-84.

1958. Pathogenesis of root-knot

nematodes to the Puerto Rico
variety of sweet potato.
Phytopathology 48: 30-39.

1947. The relative susceptibility of
41 sweet pototo varieties,
introductions and seedlings to the
root-knot nematode, Heterodera
marioni (Cornu) Goodey. Proc.
Helminthol. Soc. Wash., D.C. 14:
20- 23.

MALO, S.E. 1960. Nature of resistance
of "Okinawa" and "Nemagurd"
peach to the root-knot nematode,
Meloidogyne javanica. Proc.
Amer. Soc. Hort. Sci. 90: 39-46.

1964. Root-knot histogenesis
Contr. Boyce Thompson Inst. PI
Res. 22: 471-490.

1972. Transfer cells. Ann. Rev.
Plant Physiol. 23: 173-196.

1970. Giant cells formation in
tomato roots caused by
Meloidogyne incognita and M.
hapla (Nematodea) infection. A

Philipp. Phytopathol. 1994, Vol. 30(2):74-80

light and electron microscope
study. Can. J. Botany 48:

POWELL, N.T. 1962. Histological basis
of resistance to root-knot
nematodes in flue-cured tobacco
(Abstr.). Phytopathology 52: 25.

1959. Studies on resistance in
tomato to root-knot nematodes
and on the occurrence of patho-
genic biotypes. Phytopathology
49: 716-724.

VAN GUNDY, S.D. and J.D.
KIRKPATRICK. 1964. Nature of
resistance in certain citrus
root-stocks to citrus nematode.
Phytopathology 54: 419-427.

WEIMER, J.L. and L.L. HARTER. 1925.
Varietal resistance of sweet
potato to nematodes Heterodera
radicicola (Greeff) Muller in
California. Phytopathology 15:

YU, M.H. and .E. STEELE. 1981.
Host-parasite interaction of
resistant sugar beet and
Heterodera schactii. J. Nematol.
13: 206-212.

Philipp. Phytopathol. 1994, Vol. 30(2):81-92



Portion of the M.S. thesis of the junior author.

Professor and former graduate student, respectively, Department of Plant
Pathology, College of Agriculture, University of the Philippines at Los Baios,
College, Laguna. Present address of the junior author: Zamboanga del Norte
Agricultural College, Tampilisan, Zamboanga del Norte.

Key words: Bioact, chicken dung, Meloidogyne incognita, phenamiphos,
Rotylenchulus reniformis, tomato yield, urea.


In a pot experiment, soil incorporation of low and high
rates of chicken dung (equivalent rates of 2.5 and 5.0
tons/ha) and the nematicide-insecticide phenamiphos
(equivalent rates of 2.5 and 5.0 kg a.i./ha) and soil
drenching with the biological nematicide Bioact (equivalent
rates of 10 g/40 I water and 10g/25 I water/ha) were found
equally effective against Meloidogyne incognita,
Rotylenchulus reniformis and other nematodes on tomato.
The range of percentage reductions in nematode populations
at the end of cropping was 53.3 to 63.1. The nematode
control provided by these treatments was reflected by
comparable increases in plant top weight and yield and in
reduction in root galling. The inorganic fertilizer urea,
incorporated to the soil at the equivalent rates of 60 and 96
kg N/ha, also reduced the nematode populations.

In a subsequent laboratory study using approximately
the same rates as in the pot experiment, crude chicken dung
extract at 1:0 (equivalent to the high rate in the pot
experiment) and 1:10 dilution ratios, phenamiphos at 20 and
40 ppm concentrations also caused significant nematode
mortalities in Petri dishes, with the higher concentrations
being more effective than the lower. Chicken dung extract
dilution ratios of 1:100 and 1:1,000, urea concentrations of
10 ppm and 170 ppm and Bioact spore concentrations of 5
and 10 million in 5 ml suspensions did not affect the

Nematicidal factors present in chicken dung were
identified. These were the formic, propionic, acetic, and
butyric acids, and two species of nematophagous fungi
namely, Arthrobotrys oligospora and Dactylaria brochophaga,
with the former fungus exhibiting higher nematode trapping
efficiency than the latter.


Inexpensive non-chemical methods
of controlling plant nematodes have
recently been the focus of
investigations in the Philippines. These
methods include use of organic soil
amendments and biological control.
Among the soil amendments tested,
chicken dung was the most effective in
field experiments (Duhaylongsod and
Castillo, 1989; Karmacharya and
Castillo, 1986). In these experiments,
chicken dung not only controlled the
nematodes, but also increased crop
yield presumably due to its high
nutrient content. On tomato, pre-
planting furrow application of the dung
at the rate of 5.0 tons/ha, or 375
g/linear m of furrow gave an added
return, excluding labor costs, of
P13,943.00/ha over the non-treated
check compared to only P1,608.00/ha
obtained from the application of the
nematicide phenamiphos at the rate of
5.0 kg a.i./ha.

Success in field control of the
root-knot nematode Meloidogyne
incognita by the fungus Paecilomyces
lilacinus (Thom) Samson with
consequent potato yield increase
(Jatala, et al., 1979) has renewed zeal
in biocontrol studies. BIOACT (formerly
BIOCON), a new commercially avai-
lable biological nematicide containing
P. lilacinus (Philippine isolate) is
effective against nematodes attacking
cabbage, tomato, cauliflower, brocolli,
and potato (Davide and Zorilla, 1985).
It can be mixed with the soil, used as
soil drench around plants or planting
materials or dipped in BIOACT solution
before planting.

Urea was reported to have a
nematicidal property (Singh and
Sitaramaiah, 1967; Walker, 1971).
However, other investigations (Mishra
and Prasad, 1974; Karmacharya and
Castillo, 1986) yielded negative

The present study aimed to
compare the effectiveness of chicken
dung, BIOACT, urea, and the
nematicide phenamiphos in controlling

Philipp. Phytopathol. 1994, Vol. 30(2):81-92

plant parasitic nematodes under pot
and laboratory conditions.



Soil used in the experiment. Soil
infested mostly with the nematodes,
identified as root-knot (M. incognita)
and reniform (R. reniformis) nematodes
was collected from a tomato farm in
San Joaquin, San Pablo City.
Populations of the nematodes were
increased on 20 potted tomato for 85
days. The soil from all pots was
thoroughly mixed, obtained 15 50-cm
aliquot samples and processed for
nematodes using the Baermann funnel
technique. Average nematode counts,
obtained from these samples 3 days
after setting in the funnels, were 426
root-knot and 120 reniform nema-
todes. The average total population of
the other nematode genera (Helicoty-
lenchus, Hoplolaimus, Pratylenchus,
Tylenchorhynchus, Hemicricone-
moides, and Xiphinema) was very low,
consisting only of about' 3% of all
nematodes counted. After the nema-
tode increase, 45 No. 8 pots were
filled with the pooled soil. Five
additional pots were filled with the
same soil but drenched with 6%
Formalin to kill the nematodes.

Growing the test seedlings. Toma-
to (Lycopersicon esculentum Mill., cv.
VC 11-1) seedlings started from seed-
boxes containing a mixture of one part
sand, one part compost and one part
garden soil, were used as test plants.
Prior to sowing, the soil was sterilized
by drenching with 6% commercial
Formalin at the rate of 1 liter per
approximately 0.0283 m of soil and
kept sealed by means of a plastic cover
for 3 days. The sterilized soil was then
exposed to dry on a wide plastic sheet
until the smell of Formalin disappeared.
Seven-day old seedlings were
transplanted singly to 7.5 x 10 cm
plastic bags containing soil treated
with 6% Formalin. Transplanting of the
seedlings (one per pot) to the pots
used in the experiment was done when
they were 2 weeks old.

Philipp. Phytopathol. 1994, Vol. 30(2):81-92

Experimental design and
treatments. In a randomized complete
block design with five replications, 10
treatments were assigned to the pots
before transplanting. The treatments
consisted of a sterile soil check (soil
treated with Formalin), non-treated
check and two levels each of
phenamiphos (Nemacur 10G), chicken
dung, urea and BIOACT.

Based on the surface area of the
No. 8 pots used in the experiment
(20.32 cm diam or 0.032429 sq. m.),
the low (0.08 g/pot) and high (0.16
g/pot) rates of phenamiphos applied
were equivalent to 2.5 and 5.0 kg
a.i./ha respectively. For chicken dung,
the low (8.11 g/pot) and high (16.22
g/pot) rates applied were equivalent to
the effective rates 2.5 and 5.0
tons/ha, respectively, used by
Karmacharya and Castillo (1986). For
urea, the low (0.42 g/pot) and high
(0.68 g/pot) rates applied were
equivalent to the recommended 60 and
96 kg N/ha (PCARRD, 1975),
respectively, while for BIOACT, the
low and high rates applied were based
on the per hectare recommended
suspension rates of 10 g/40 I water (1
million spores/ml) and 10 g/25 I water
(2 million spores/ml), respectively
(Davide and Zorilla, 1985). Chicken
dung, phenamiphos and urea were
thoroughly mixed with the nematode-
infested soil in their respective pots a
day before transplanting, while
BIOACT was applied by pouring the
suspension around the base of the
plant immediately after transplanting.

The chicken dung used in the
experiment was less than 7 weeks old
when applied. The moisture and
nutrient contents of the dung were as
follows: Moisture, 12.4%, N, 2.6;
P205, 3.64; K20, 3.37. The acid
contents were formic (0.08%), acetic
(0.69%), propionic (0.63%), and
butyric (0.25%).
Care of experimental plants. The
test plants were placed on a cement
floor outside the greenhouse. The pots
were kept weed-free and moisture was
supplied to the plants, whenever
necessary. Control of insect and
diseases was provided by forthnightly

foliar spraying with either
monocrotophos or malathion and
benomyl or mancozeb, respectively.
While spraying, precautions were
made to make sure that contamination
of the soil with the chemicals was


Plant reactions. After 3.8 months
from planting, data on top weight, root
weight and root galling were collected.
The severity of root galling was
determined, based on relative
percentages of galled portions of the
root system. The following 1-5
severity rating scale (Castillo, 1969)
was used: 1, 0% (no galling); 2, 1-
25% (light); 3, 26-50% (moderate); 4,
51-75% (severe); 5, over 75% (very

Collection of yield data was made
as soon as the first fruit matured until
the termination of the experiment.

Nematode populations. At the
termination of the experiment, the soil
in each pot was thoroughly mixed, the
roots were washed and chopped 1 to
2 cm pieces and then 50-cm soil and
1 g feeder root samples randomly
obtained. The nematodes were then
extracted from the soil sample using
the Baermann funnel technique,
following the procedure used by
Karmacharya and Castillo (1986). The
nematodes were allowed to settle at
the bottom of the funnel for 72 hr and
then counted with the use of a
dissecting microscope. The root
sample was stained in acid fuchsin-
lactophenol (McBeth et al., 1941). The
presence and number of nematodes in
the stained roots were determined by
crushing a few root pieces at a time
between two glass slides and
examining them under a dissecting


Effect of Treatments on Nematode
Larvae. Comparison of the
effectiveness of chicken dung,
phenamiphos, urea, and Bioact against
M. incognita and R. reniformis in vitro

was also made in two separate tests in
Petri dishes in the laboratory. The
concentrations used in each of these
tests were similar with the application
rates used in the pot experiment,
based on the volume of the soil (4,000
cc) in each of the pots used in the

In the case of chicken dung, the
high application rate of 16.22 g/pot
was used. Thus, 0.41 g dung was
thoroughly mixed with 100 ml of
water. The crude extract was passed
through an ordinary Whatman filter
paper to an Erlenmeyer flask. Various
dilutions of crude extracts, namely,
1:0, 1:10, 1:100 and 1:1,000 were
prepared. The low and high rates of
phenamiphos (0.08 and 0.68 g/pot,
respectively), urea (0.42 and 0.68
g/pot, respectively) and Bioact (10 ml
of 10 g/40 I and 10 ml of 10 g/25 I
suspension rates, respectively) were
the same rates used. The equivalent
concentrations were computed, as
respectively, 20 and 40 ppm for
phenamiphos, 105 and 170 ppm for
urea, and 5 and 10 million spores in 5
ml suspension for BIOACT.

Five ml each of the different
concentrations of the materials to be
tested and a distilled water check,
replicated four times, were placed in
each Petri dish. A suspension
containing approximately 100 newly
hatched active nematode larvae from
the same nematode cultures used in
the pot experiment was pipetted into
each dish. After 48 hr, the number of
dead larvae in each dish was
determined, following the staining
method used by Jatala (1969).
Counting of the dead nematodes was
done with the use of a dissecting

Isolation and identification. A 3-
mm cube of chicken dung from the
same batch as that used in the pot and
laboratory experiments was introduced
at the center of a plated corn meal
agar. After 1 week, transfers of each
fungus present were made by the
single spore method (Duddington,
1956). Identification to species of the
different fungi was based on

Philipp. Phytopathol. 1994, Vol. 30(2):81-92

measurements of conidia used by
Cooke and Godfrey (1964).

Predaceous efficiency. The
predacity of the nematophagous fungi
isolated from chicken dung was
determined in plated corn meal agar. A
3-mm cube of agar block containing
the mycelium of each of the
nematophagous fungus species was
introduced at the center of each Petri
dish. Each fungus species was
introduced in four replicate dishes. The
same number of dishes with corn meal
agar, but without the fungus, was
provided as check. One ml aliquot
suspension, containing approximately
100 newly hatched nematode larvae
was pipetted into each dish. After 96
hr, the percentage of trapped
nematodes in each dish was
determined with the aid of a dissecting
microscope. The predacity of each
fungus species was tested on
M. incognita and R. reniformis from the
same nematode cultures used In earlier
experiments in two separate



Effects of Treatments on
Nematode Populations. The average
numbers of plant parasitic nematode
populations recovered per 50 cm soil
and 1 g roots at final harvest of potted
tomato are shown in Table 1. These
nematodes consisted of M. incognita
(85%), R. renformis (11.89%), and
other genera (2.3%). Since the sterile
soil check pots did not contain any
plant parasitic nematodes, this
treatment was excluded from the
analysis of nematode populations.

The low and high rates of chicken
dung, phenamiphos and BIOACT
application equally reduced the plant
parasitic nematode populations in the
soil. The percentage reductions ranged
from 46.2 (low chicken dung) to 58.3
(high BIOACT). Both low and high
rates of urea likewise reduced the soil
populations (18.1 and 18.0,
respectively), but to a lesser degree.

Philipp. Phytopathol. 1994, Vol. 30(2):81-92

Table 1. Populations of plant parasitic nematodes during last harvest of potted
tomato treated with low and high rates of chicken dung, phenamiphos,
urea and BIOACT.1

Per Per Per
TREATMENT2 50 cm3 soil (%) 1 g roots (%) 50 cm3 soil and (%)
1 g roots

Untreated check 630.2 c 1101.4 d 1731.6 d
Low chicken dung 338.8 a 46.2 469.0 b 57.4 807.8 b 53.3
High chicken dung 299.6 a 52.5 370.0 a 66.4 669.6 ab 61.3
Low phenamiphos 337.4 a 46.5 368.4 a 66.6 705.8 ab 59.2
High phenamiphos 304.8 a 51.6 353.8 a 67.9 658.6 ab 62.0
Low urea 516.0 b 18.1 948.6 c 13.9 1464.6 c 15.4
High urea 516.6 b 18.0 892.2 c 19.0 1408.8 c 18.6
Low BIOACT 301.0 a 52.2 385.8 ab 65.0 686.8 ab 60.3
High BIOACT 262.6 a 58.3 375.6 ab 65.9 638.2 a 63.1

1Data are means of five replicates. Means with similar letters in a column indicate no
significant difference at 5% level with DMRT. Total nematode populations consisted of M.
incognita (85.9%), R. reniformis (11.8%) and other genera (2.3%).

2Application rate/pot: Low chicken dung = 8.11 g (2.5 t/ha), High chicken dung = 16.22 g
(5.0 t/ha); Low phenamiphos = 0.08 g (2.5 kg a.i./ha), High phenamiphos = 0.16 g (5.0 kg
a.i./ha); Low urea = 0.42 g (60 kg N/ha), High urea = 0.68 g (96 kg N/ha); Low B1OACT =
10 ml of 10 g/40 liter suspension, High BIOACT = 10 ml of 10 g/25 liter suspension.

3Reduction (%) = (Untreated check Treated)/Untreated check 100

In 1 g root samples, high chicken
dung, low and high phenamiphos and
low and high BIOACT rates reduced
the plant parasitic nematode popula-
tions the most, followed by low
chicken dung and by low and high
rates of urea. Percentage reductions
ranged from 13.9 (low urea) to 67.9
(high phenamiphos).

The total plant parasitic nematode
population in 50 cm3 soil and 1 g roots
.ere reduced by all the treatments.
he percentage reductions ranged from
15 4 (low urea) to 63.1 (high
BIOACT). Best control was equally
provided by high chicken dung rate and
low and high rates of both
phenamiphos and BIOACT, followed by
low rate of chicken dung. Low and
high rates of urea were the least
effective in reducing the total
nematode populations,

Effect of Treatments on Plant
Reaction and Yield Components. Top
growth, root growth, root galling and
yield of tomato, as affected by the
applications of chicken dung,
phenamiphos, urea and BIOACT are
shown in Table 2.

Low and high rates of chicken
dung, phenamiphos and BIOACT
applications increased the top weight
of tomato, based on the non-treated
check. Low and high rates of urea did
not increase the top weight. The
highest top weight was obtained in the
sterile soil check.

Highest root weight was obtained
in sterile soil check. Root weights in all
treated and non-treated check pots
were comparable.

Philipp. Phytopathol. 1994, Vol. 30(2):81-92

Table 2. Reactions of tomato to plant parasitic nematodes in pots applied with low
and high rates of chicken dung, phenamiphos, urea and BIOACT.1

(wt. in g) (wt. in g) GALLING3 (g)

Sterile soil check 112.3 c 20.3 b 1.0 a 207.7 d

Non-treated check 15.0 a 12.2 a 4.8 c 4.4 a

Low chicken dung 36.3 b 11.4 a 3.6 b 48.4 c

High chicken dung 41.0 b 11.8 a 3.4 b 77.4 c

Low phenamiphos 39.5 b 13.8 a 3.8 b 57.7 c

High phenamiphos 45.0 b 11.8 a 3.4 b 72.0 c

Low urea 14.2 a 11.8 a 4.6 c 18.0 b

High urea. 14.5 a 11.7 a 4.6 c 14.4 b

Low BIOACT 41.7 b 12.8 a 3.4 b 54.1 c

High BIOACT 41.3 b 11.5 a 3.4 b 65.6 c

1Data are means of five replicates.
difference at 5% level with DMRT.

Means with similar letters in a column indicate no significant

2Applicatior ,.te/pot: Low chicken dung = 8.11 g (2.5 t/ha), High chicken dung = 16.22 g (5.0 t/ha);
Low pheanmiphos = 0.08 g (2.5 kg a.i./ha), High phenamiphos = 0.16 g (5.0 kg a.i./ha); Low urea =
0.42 g (60 kg N/ha); High urea = 0.68 (96 kg N/ha); Low BIOACT = 10 ml of 10 g/40 liter suspension,
High BIOACT = 10 ml of 10g/25 liter suspension.

3Based on relative percentage of galled portions of root systems as follows: 1, 0% (no galling), 2, 1-25%
(light); 3, 26-50% (moderate); 4, 51-75% (severe); 5, over 75% (very severe).

Root galling was reduced by low
and high rates of chicken dung, phena-
miphos and BIOACT applications. Low
and high rates of urea applications did
not reduce root galling. Plants in the
sterile soil check did not show any

Highest yield was obtained in
plants grown in pots with sterile soil.
Applications of low and high rates of
chicken dung, phenamiphos and

BIOACT resulted in better yield than in
the non-treated check. The low and
high rates of urea also increased the
yield, but to a lesser degree.


Effect of Treatments on Nematode
Populations. Mortality of M. incognita
and R. reniformis larvae (tested sepa-
rately) 48 hr ifter immersing in chicken
dung extract, phenamiphos and urea

Philipp. Phytopathol. 1994, Vol. 30(2):81-92

solutions and BIOACT suspensions are
shown in Table 3.

In two separate tests, crude
chicken dung extract (1:0) caused the
highest percentage mortality of M.
incognita based on the check (tap
water), followed by high phenamiphos
and 1:10 chicken dung extract dilution

Similar trend of percentage
mortality was observed in R. reniformis
larvae, except that low phenamiphos
was also equally effective against the
nematode as 1:10 chicken dung
extract dilution ratio.

The effects of the other
treatments on the percentage mortality
of the nematodes were similar to that
of the check (tap water).

Species of Nematophagous Fungi
Detected in Chicken Dung. Two
species of nematophagous fungi were
detected on chicken dung, based on
measurements of conidia following the
key used by Cooke and Godfrey
(1964). The descriptions of the conidia
of the two isolates were as follows:

Arthrobotrys oligospora Fres.
Conidia were produced in groups of 10
or more at the tip of the conidiophore
or in whorls. Color of conidia is
hyaline, shape is ovoid, uniseptate and
slightly constricted at the septum.
Measurements of 50 conidia from corn
meal agar culture ranged from 16.8 u
to 32.9 u x 9.4 u -15.2 u (24.8 u x
12.3 u). Type of trapping mechanism
is sticky net-like hyphae.

Dactylaria brochopaga Dresch.
Four to six conidia are usually pro-
duced at the tip of the conidiophore.
Color of conidia is hyaline. They are
straight or slightly curved, cylindrical
or elongate ellipsoidal, broadly rounded
at the apex and attenuated at the base
and mostly 3-septate. Measurements
of 50 conidia ranged from 16.6 u -
36.5 u x 5.62 u 7.2 u (26.55 x 6.41
u). Trapping mechanism is constricting

Predaceous Efficiency of the
Nematode-trapping Fungi. Arthrobotrys
oligospora had higher trapping efficie-
ncy on M. incognita (54%) and
R. reniformis (60%), than D.
brochopaga. The trapping efficiency of
the latter were only 44% for M.
incognita, 52% for R. reniformis. None
of the M. incognita and R. reniformis
larvae was observed trapped in the
plain corn meal agar check (Table 4).


The low and high rates of
chicken dung (8.11 g/pot andi 16.22
g/pot, respectively), phenamiphos
(0.08 g/pot and 0.16 g/pot,
respectively) and BIOACT as soil
drench (10 ml of 10 g/40 liter
suspension and 10 ml of 10 g/25 liter
suspension, respectively) were gene-
rally equally effective against
M. incognita, R. reniformis and other
genera in potted tomato at the
final harvest. Percentage reductions in
total populations (from 50 cm soil
and 1 g roots) was 53.3 (low chicken
dung) to 63.1 (high BIOACT). Urea
appears to be nematicidal, -since it
also controlled the nematodes in the
soil and in the roots, although only
to a lesser degree. The applications
of low and high rates of chicken
dung, phenamiphos and BIOACT not
only reduced the nematode populations
at the final harvest but also resulted
in comparable increases in top weight,
reduction in root galling and increase in
yield. The nematode-suppressive effect
of the application of low and high rates
of urea was only reflected in the lower
yield increase, compared to the non-
treated check.

Despite the nematode-suppressive
effects of these treatments, none
resulted in yield comparable to that in
the sterile soil check. This suggested
the capacity of plant parasitic
nematodes, particularly at the high
initial populations used in the pot
experiment, to reduce tomato yield.

88 Philipp. Phytopathol. 1994, Vol. 30(2):81-92

Table 3. Mortality of Meloidogyne incognita and Rotylenchulus reniformis larvae in
two separate tests 48 hr after immersing in various solutions of treatment

M. incognita R. reniformis

Check (pure water)

Chicken dung extract




Low phenamiphos

High phenamiphos

Low urea

High urea

4.6 ab

32.7 e
9.0 c
3.4 ab
3.2 ab

3.7 ab

4.2 abc

7.6 bc

22.7 d

2.3 a

2.3 a

2.6 a

31.3 d
10.2 b
3.2 a
2.7 a

4.0 a

3.6 a

13.0 b

22.9 c

3.1 a

2.9 a

1Data are means of four replicates. Means
difference at 5% level with DMRT.

v/ith similar letters in a column indicate no significant

2Rates used: Chicken dung extract = 5 ml from each dilution ratio; Low phenamiphos = 5 ml of 20 ppm,
High phenamiphos = 5 ml of 40 ppm; Low urea = 5 ml of 105 ppm, High urea = 5 ml of 170 ppm;
Low BIOACT = 5 million spores in 5 ml suspension of 10 g/40 liter rate, High BIOACT = 10 million
spores in 5 ml suspension of 10 g/25 liter rate.

3Mortality (%) = (Total number of larvae Number of live larvae)/Total number of larvae 100

Philipp. Phytopathol. 1994, Vol. 30(2):81-92

Table 4. Trapped Meloidogyne incognita and Rotylenchulus reniformis 96 hr after
expos re to cultures of two nematode-trapping fungi in two separate

M. incognita R. reniformis

Plain corn meal agar
(check) 0 a 0 a

Corn meal agar +
A. oligospora 54 c 60 c

Corn meal agar +
D. brochopaga 44 b 52 b

1Data are means of four replicates. Analysis were based on transformed (log x
letters indicate no significant difference at 5% level with DMRT.

+ 1) values. Similar

2Trapped Nematode (%) = (Total number of larvae Number of larvae in untreated check)/Total number
of larvae 100

Nematicidal factors believed to be
among those responsible for the
effectivity of chicken dung in
controlling plant parasitic nematodes
were identified in this study. These
were the formic, propionic, acetic, and
butyric acids, and two species of
nematophagous fungi, namely, A.
oligospora and D. brochopaga Sayre et
al. (1965), reported these acids to be
among the toxic products of organic
matter decomposition. Increase in the
number of nematode enemies was
earlier suggested (Sayre, 1971) as one
of nematicidal factors involved. The
observation of the effectivity of
nematophagous fungi in trapping the
nematodes in the study further
confirmed this observation. Fresh
chicken dung was earlier found
(Duhaylongsod and Castillo, 1984) to
be more effective in controlling
nematodes than composted dungs
suggesting that heat plays a greater
role in suppressing the nematodes than
the toxic products of decomposition. It
is probable that this increase in
nitrogen content due to chicken dung
application was partly responsible for
the observed increase in yield.

Phenamiphos is a systemic nema-
ticide. The main effect on nematodes is
acetylcholinesterase inhibition. Acetyl-
cholinesterase is an enzyme essential
in the breakdown of acetylcholine,
which is a transmitter substance for
the signals to the muscular system.
When this enzyme is inhibited,
acetylcholine accumulates, which re-
sults in convulsions, paralysis and
finally death (Chemagro Technical In-
formation, 1976). Phenamiphos is
practically nonvolatile. When incor-
porated into the soil, there is prolonged
effect on nematode control. This is
probably another reason why the low
and high phenamiphos rates were
effective in reducing plant parasitic
nematode populations up to the final
harvest. The effectiveness of
phenamiphos against M. incognita and
R. reniformis in field soil were earlier
reported (Calinga, 1979; Hirunsalee,
1981; Duhaylongsod and Castillo,
1984; Karmacharya and Castillo,

The effectiveness of BIOACT as a
soil drench was confirmed in this
study. P. lilacinus, the nematophagous

fungus, which is basically an egg
parasite in BIOACT appeared to be
very effective in infecting and
destroying the eggs of M. incognita, R.
reniformis and other plant parasitic
genera. The fungus spreads rapidly and
remains in the soil for a long time, a
desirable characteristic of a successful
and competitive biological control
agent (Jatala, 1985). These are
probably the reasons why both low
and high rates of BIOACT reduced the
plant parasitic nematode populations at
the final harvest.

The lesser reduction in nematode
populations due to applications of low
and high rates of urea, as compared to
those due to applications of low and
high rates of chicken dung, phenami-
phos and BIOACT, was reflected in a
similarly lower yield increase in the pot
experiment. Although only to a lesser
degree, it appeared that urea is also
effective against plant parasitic
nematodes under the conditions of the
experiment. While some workers found
urea to be nematicidal at the high rate
of 978 kg/ha (singh and Sitaramaiah,
1967), other workers found this
material to be ineffective at 282 and
424 kg/ha (Mishra-and Prasad, 1974)
and 112 and 224 kg/ha (Karmacharya
and Castillo, 1986) in field
experiments. It is possible that the
limited space and enclosed condition in
the pot was conducive to the toxic
effect of urea on the nematode.

In separate laboratory study, only
the effectiveness of chicken dung on
the R. reniformis and M. incognita
(1:0 and 1:10 extract dilution ratios)
and phenamiphos on both nematodes
(20 and 40 ppm) and only at 40 ppm
for M. incognita were confirmed. The
1:100 and 1:1000 chicken dung
extract dilution ratios, the low and high

Philipp. Phytopathol. 1994, Vol. 30(2):81-92

urea solution rates and the low and
high BIOACT suspension rates did not
affect the test larvae of M. incognita
and R. reniformis. Calinga (1979)
observed 100% mortality of nematode
test larvae in chicken dung probably
because he used 2 kg of chicken dung
added to 1 liter of water to get the
crude extract. While in the present
study, 0.41 g chicken dung, based on
the high rate of 16.22 g used in the
pot experiment, was mixed with 100
cc of water. The resultant crude
extract may have contained low
concentration of volatile fatty acids as
confirmed by the low percentage
mortality of M. incognita and R.
reniformis larvae, compared to the
results in the former study. But, this
demonstrated a realistic view of the
effects of chicken dung on the
populations of nematodes and
reactions of tomato plants in the pot
experiment since the high chicker
dung on the populations of nematodes
and reactions of tomato plants in the
pot experiment was the same base rate
used in the laboratory study. That the
1:0 dilution ratio of chicken dung
extract was more nematicidal than the
5 ml of 40 ppm of phenamiphos was
also shown in this study.

The negative effect on nematode
mortality of low and high BIOACT
suspension rates was probably due to
the short exposure duration (only 48
hr) to the fungus and to the growth-
unfavorable water medium used in the
experiment. Failure of P. lilacinus to
show its toxic effect on nematodes
was likewise observed by Molina

Feasibility studies, preferably
under farmers' field conditions, are
necessary for a better evaluation of the
test materials used in this study.

Philipp. Phytopathol. 1994, Vol. 30(2):81-92


CALINGA, R.H. 1979. Field and
laboratory studies on the
effectiveness of dungs for the
control of plant parasitic
nematodes on cowpea. M.S.
Thesis. University of the
Philippines at Los Baios, College,

CASTILLO, M.B. 1969. Host-parasite
relationships with definition of
peanut resistance to the northern
root-knot nematode, Meloidogyne
hapla. Ph.D. Thesis. Oklahoma
State University, Stillwater,

TION. 1976. Nemacur nematidice.
Chemagro Agr. Div., Kansas City,
Missouri. 114 p.

1964. A key to the nematode
destroying fungi. Trans. Brit.
Mycol. Soc. 47: 61-74.

1985. Fungi control potato cyst
nematode. Research at Los Baios.
4: 4-5.

CASTILLO. 1989. Plant parasitic
nematode populations and tomato
(Lycopersicon esculentum Mill.)
reactions in soil amended with
fresh and composted organic

DUDDINGTON, C.L. 1956. The friendly
fungi. 188 p. London: Faber and

HIRUNSALEE, A. 1981. Plant parasitic
nematode population and mung-
bean Vigna radiata (L.) Wilczek
reactions in soil treated with
phenamiphos and organic amend-
ments. M.S. Thesis. University of
the Philippines at Los Baios,
College, Laguna.

JATALA, P. 1969. A new staining
technique for differentiating live
and dead nematodes. Phytopatho-
logy p. 1033 (Abstr.).

BOCANGEL. 1979. Biological con-
trol of Meloidogyne incognita
acrita and Globodera pallida on
potatoes. J. Nematol. 11: 303

CASTILLO. 1986. Plant nematode
populations and tomato
(Lycopersicon esculentum Mill.)
yield in field plots with chicken
dung, sawdust and urea. Phil.
Agr. 69: 289-305.

A.L. SMITH. 1941. Note on
staining nematodes in root
tissues. Helminthol. Soc. Wash.
Proc. 8: 26.

1974. Effect of soil amendments
on nematodes and crop yield. I.
Oil-seed cakes, organic matter,
inorganic fertilizers and growth
regulators on nematodes
associated with wheat and their
residual effect on mungbean.
Indian J. Nematol. 4: 1-19.

MOLINA, G.C. 1985. Potentials of
microorganisms as biological
control agents of selected plant
pathogens. Ph.D. Thesis.
University of the Philippines at Los
Baios, College, Laguna.

THORPE. 1965. Identification and
selection nematicidal components
in extracts of plant residue decom-
posing in soil. Nematologica 11:

SAYRE, R.M. 1971. Biotic influences
in soil environment. In B.M.
Zuckermann, W.F. Mai and R.A.

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Rhodes, eds. 1971. Plant parasitic
nematodes. I. Morphology,
anatomy, taxonomy and ecology.
Acad. Press, New York and
London. pp. 235-256.

1967. Effect of decomposing
areen leaves, sawdust and urea on

the incidence
and tomato.
20: 349-355.

of rootknot of okra
Indian Phytopathol.

WALKER, M.A. 1971. Population of
Pratylenchus penetrans relative to
decomposing nitrogenous soil
amendments. J. Nematol. 3: 43-

Philipp. Phytopathol. 1994, Vol. 30(2):93-99



Respectively, University Researcher, Emeritus Professor and Associate
Professor, University of the Philippines at Los Baios, College, Laguna.

Key words: Bacterial wilt, cultural control, ecology, Pseudomonas
solanacearum, survival.


Survival of Pseudomonas solanacearum biovar 3 was
studied in rice-tomato cropping patterns. High survival rates
were associated with tomato plantings. Two consecutive
tomato plantings consistently sustained high population of
the bacterium. Rice-based cropping patterns seriously
affected the survival of P. solanacearum in the soil. The
bacterium was no longer recovered after three consecutive
rice plantings. Two consecutive rice plantings sharply
reduced the population, but failed to eliminate the pathogen
in the soil. Bacterial wilt incidence was substantially reduced
when tomato plants were planted after rice and tended to
increase when followed by another tomato planting. Tomato
plants planted after two consecutive rice planting remained
healthy throughout the growing period.

Results of flooding experiment clearly suggested that the
significant reduction in the population of P. solanacearum in
rice-tomato cropping pattern was primarily due to flooding
associated with lowland rice culture.


Bacterial wilt, caused by
Pseudomonas solanacearum E.F.
Smith, is one of the most destructive
tropical diseases of solanaceous crops.
The pathogen has a broad host range.
and reportedly affects more than 50
families of plants (Hayward, 1994). It
is also known to persist in the
environment in association with host
and non-host crops without showing
any apparent symptom making disease
control more difficult. Yield reduction
due to the disease in the Philippines

was estimated at 15% in tomato and
5% for both eggplant and pepper
(Zehr, 1969). In Taiwan, the average
wilt incidence in hybrid tomatoes was
15-26% and 55% on moderately
resistant and susceptible hybrids,
respectively, and losses of over 12
million US dollars occurred annually on
fresh market hybrid tomatoes (Hartman
et al., 1991).

One of the most successful
approaches in reducing the occurrence

of bacterial wilt is by cultural
management. Modification of cropping
patterns is known to reduce the
incidence of bacterial wilt. The high
incidence of bacterial wilt in fields
planted to potato, tomato and eggplant
rapidly declined when rotated with
maize, finger millet or rice (Elphinstone
and Aley, 1993; Wang et al., 1983;
Sohi et al., 1981). Two-year rotation
with non-host crop, such as rice or
maize, was sufficient to control wilt
but longer rotations resulted to even
better control (Machmud, 1993).
Flooding of field for lowland rice
production reportedly decreased the
incidence of bacterial wilt (Tung,
1986; He, 1990; Machmud, 1993).
However, there have been few studies
to explain how various cropping
patterns may reduce the bacterial wilt
incidence or relate the reduction of wilt
incidence with the population level of
P. solanacearum.

This study was conducted to
determine the survival of
P. solanacearum biovar 3 in artificially
infested soil subjected to rice-tomato
cropping patterns and the survival of
P. solanacearum in flooded and
unflooded soil conditions.


Effect of Cropping Pattern on the
Survival of P. solanacearum

The Experimental Materials. Top
soils from fields previously planted to
tomato and rice were collected,
thoroughly mixed, disinfested by
baking, and placed in 35-cm diameter
clay pots previously plugged with
cement ahd painted with black coaltar.
All pots were planted to tomato
seedlings cv. Yellow Plum. After the
establishment of tomato plants, the
soil in each pot was infested with
P. solanacearum, biovar 3 from
tomato, by pouring 50 ml of bacterial
suspension standardized at about 107
cells per ml. When the tomato plants
showed wilting, the soils were
removed from the pots, thoroughly
mixed, and put back in the pots. The

Philipp. Phytopathol. 1994, Vol. 30(2):93-99

pots were planted with bacterial wilt
susceptible tomato (cv. Yellow Plum)
and lowland rice (cv. IR 68).

The Experimental Treatments.
Eight cropping patterns involving rice
and tomato crops were simulated on
potted soil infested with
P. solanacearum, biovar 3. Fig. 1
summarized the different treatments
which were replicated 3 times and
arranged in completely randomized
design. To simulate the lowland rice
conditions, potted soils planted with
rice were continuously flooded for 90
days with the amount of water
maintained at approximately the same
level throughout the growing period.
After harvesting, the soil was drained,
cultivated and planted with tomato

Survival of P. solanacearum. To
determine the survival of P.
solanacearum in the soil, the
population was monitored at monthly
intervals for the whole duration of the
experiment. For every sampling period,
five soil samples taken equidistantly
within 30 cm depth by soil auger were
collected from each treatment, mixed
thoroughly, put in labelled plastic bag
and stored in refrigerator for
subsequent dilution planting.

From each composite soil sample,
a 10-gram soil was placed in a 250-ml
sterilized Erlenmeyer flask containing
90 ml sterile water. The resulting
suspension was shaken for 30 min at
200 rpm and serially diluted up to
10-6. About 0.1 aliquot of each dilution
was spread on a plated SM-1 medium
with the following: crystal violet
(50ug/ml), thimorosal (5 ug/ml),
polymixin B sulfate (100 ug/ml),
tyrothrycin (20 ug/ml) and
chloromycetin (5 ug/ml) (Granada and
Sequeira, 1983). The plates were then
incubated at 32C for 72 hr and typical
colonies of P. solanacearum were

Data Analysis. The population
densities of P. solanacearum (per gram
of soil) were calculated. The data were
transformed using square root

Philipp. Phytopathol. 1994, Vol. 30(2):93-99

transformation and analysis of variance
was made.

Effect of Flooding on the Survival of
P. solanacearum

The Experimental Materials. Top
soils from lowland rice fields previously
planted to vegetables were collected,
thoroughly mixed, disinfested by
baking, and placed in 35-cm diameter
clay pots previously plugged with
cement and painted with coaltar. All
potted soils were infested with P.
solanacearum biovar 3 using the same
procedure previously described in
cropping pattern experiment.

The Experimental Treatments.
Four flooding regimes in a span of two
cropping seasons were simulated in
potted soils infested with P.
solanacearum biovar 3 (Fig. 1). To
stimulate the lowland wet conditions,

Fig. 1. Cropping pattern and flooding
experiments with their
corresponding treatments.

potted soils were continuously flooded
with water maintained at approximate-
ly the same level throughout the de-
sired period. Upland dry conditions
was also simulated by draining the soil
and maintaining soil moisture condu-
cive for the growth of tomato plant.

Survival of P. solanacearum. The
population of P. solanacearum in each
treatment was monitored using the
same procedure previously described in
the cropping pattern experiment.


Survival of P. solanacearum Biovar 3 in
Rice-Tomato Cropping Patterns

The population of P. solanacearum
biovar 3 in the artificially infested soil
decline with time regardless of
cropping pattern (Fig. 2). The rate of

Fig. 2. Survival of Pseudomonas sola-
nacearum biovar 3 in tomato-
based (A), rice-based (B) and
sequential (C) cropping

Philipp. Phytopathol. 1994, Vol. 30(2):93-99

survival was significantly influenced by
the cropping patterns (Table 1). Higher
survival rate was associated with
tomato-based cropping patterns.
Consecutive planting of tomato
consistently sustain high populations
of P. solanacearum (Fig. 2). Planting
rice after two consecutive tomato
plantings did not significantly reduce
the population of the bacterium, but
the population was substantially
reduced when tomato was proceeded
by two consecutive rice plantings.

Survival of P. solanacearum was
seriously affected by rice-based
cropping patterns. The bacterium was
no longer recovered in the soil after
three consecutive rice plantings. Two
consecutive rice plantings sharply
reduced the population but failed to
eliminate the bacterium in the soil.
Planting of tomato after rice did not
markedly increase the bacterial
population when tomato was
alternately planted with rice. The
bacterial population did not increase

The incidence of bacterial wilt in
two or three consecutive plantings of
tomato was consistently high (Table
2). Bacterial wilt incidence was
substantially reduced when tomato
plants were planted after rice and
tended to increase when followed by
another tomato planting. Tomato
plants planted after two consecutive
rice plantings remained healthy
throughout the growing period.

Effects of Flooding on the Survival of
P. solanacearum

The survival of P. solanacearum
biovar 3 in artificially infested soil
showed a general decline in all
treatments (Table 3 and Fig. 3). Soils
unflooded for the duration of first and
second eroppings yielded higher
population density of P. solanacearum.
Flooding for the duration of one
cropping significantly reduce the
population of the bacterium and further
reduction was obtained when the
flooding time was extended for another
cropping. Intermittent flooding also

Fig. 3. Survival of Pseudomonas sola-
nacearum biovar 3 in unflooded
and flooded soil conditions.

reduced the population of the
bacterium. Dry soil condition that was
proceeded by flooding did not improve
the survival of P. solanacearum.

Results of the experiment clearly
indicate that rice-based cropping
pattern can be an effective means of
controlling bacterial wilt of tomato.
The low survival of P. solanacearum in
rice-based cropping pattern can be
attributed to the changes in the
physical attributes and to the biological
changes associated with cropping
systems. Flooding associated with
transplanted lowland rice culture
adversely affects survival of
P. solanacearum primarily by depriving
the pathogen of oxygen and
secondarily by altering soil physical
structures which become detrimental
to the pathogen. The study to
determine the effect of flooding on the
survival of P. solanacearum confirms
the above findings. Understandably,
flooding adversely affects the survival
of P. solanacearum because the
organism requires oxygen for growth
and development. The results of both
experiments substantiate the control

Philipp. Phytopathol. 1994, Vol. 30(2):93-99

Table 1. Effect of rice-tomato cropping patterns on
Pseudomonas solanacearum biovar 3.

the population and survival of

PATTERN BEFORE 1st 2nd 3rd
CROPPING Cropping Cropping Cropping

T-T-T 26.5a 13.40ab 3.80ab 1.10a
T-T-R 3.0a 19.85a 6.46a 0.48a
T-R-T 17.0a 12.78ab 1.48ab 0.58a
T-R-R 18.0a 10.19ab 0.91b 0.035b
R-T-T 22.5a 2.78c 0.33b 0.375a
R-T-R 18.0a 3.12c 0.61b 0.13b
R-R-T 23.0a 2.24C 0.165b 0.035b
R-R-R 20.5a 2.66c 0.075bc 0.00b

1Means of five replications with three sampling periods; means in the column followed by a common
letter are not significantly different at 5% level, DMRT.

Table 2. Disease assessment of bacterial wilt of tomato associated with, rice-tomato
based cropping patterns for three cropping seasons.



1st Cropping

2nd Cropping

3rd Cropping

T-T-T 100.00 87.50 94.50
T-T-R 100.00 100.00
T-R-T 100.00 19.00
T-R-R 100.00
R-T-T 37.50 58.35
R-T-R 37.50
R-R-T 0.00

1 Average of 5 replications, symbol represents rice rotation.

Table 3. Survival of Pseudomonas solanacearum biovar 3 in soil with various
flooding regimes.

TREATMENT BEFORE CROPPING 1st Cropping 2nd Cropping

No Flooding (dry-dry) 24.0a 15.43a 4.08a
Intermittent Flooding
(dry-wet) 27.0a 11.28a 1.43b
Intermittent Flooding
(wet-dry) 26.5a 2.63b 0.47c
Continuous Flooding
(wet-wet) 23.5a 2.26b 0.11c

1Means in the columns followed by a common letter are not significantly different at the 5% level, LSD.

recommendation which involve
flooding of infested fields with "clean"
irrigation water continuously for six
months to control bacterial wilt. The
experiment also indicates that flooding
for 3 months or for one season has
substantially reduced the population of
P. solanacearum comparable to that of
continuous flooding for two cropping
seasons. This explains the success of
tomato production after rice in some
parts of the Philippines.

Earlier reports from Java has
indicated that flooding practices
accompanying rice cultivation did not
decrease the incidence of bacterial wilt
(Palm, 1922). Similarly, field studies in
Sri Lanka (Seneviratne, 1976)
demonstrated that flooding for several
weeks during the rice growing season
did not control the disease. Bacterial
wilt incidence after flooding can be
attributed to reinfestation of the field
from P. solanacearum contaminated
water rather than to the survival of the
pathogen in the flooded soil.


1993. Integrated control of
bacterial wilt of potato in the
warm tropics of Peru. In:
Hartman, G. L. and Hayward, A.
C. (eds.). Bacterial Wilt
Proceedings of an International
Symposium, Kaoshiung, Taiwan,
ROC, 28-30 October 1992.
ACIAR Proceedings 45, 276-83,
ACIAR, Canberra.

1983. Survival of Pseudomonas
solanacearum in soil, rhizosphere
and plant roots. Canadian Journal
of Microbiology 29: 433-440.

HARTMAN, G. L., W. F. HONG, and
WANG, T. C. 1991. Survey of
bacterial wilt on fresh market
hybrid tomatoes in Taiwan. Plant

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Protection Bulletin, Taiwan 33:

HAYWARD, A. C. 1994. The hosts of
Pseudomonas solanacearum In:
Hartman, G. L. and Hayward, A.
C. (eds.). Bacterial Wilt: The
Disease and its Causative Agent,
Pseudomonas solanacearum. CAB
International, Wallingford, Oxon,

HE, L. Y. 1990. Control of bacterial
wilt of groundnut in China with
emphasis on cultural and
biological methods. In: Middleton,
K. J. and Hayw
Bacterial Wilt of Groundnut. Pro-
ceedings of an ACIAR/ICRISAT
Collaborative Research Planning
Meeting held at Genting High-
lands, Malaysia, 18-19 March
1990. ACIAR Proceedings 31, 22-
25, ACIAR, Canberra.

MACHMUD, M. 1993. Control of
peanut bacterial wilt through crop
rotation. In: Hartman, G. L. and
Hayward, A. C. (eds.). Bacterial
Wilt Proceedings of an interna-
tional symposium, Kaoshiung,
Taiwan, ROC, 28-30 October
1992. ACIAR Proceedings 45:
221-224, ACIAR, Canberra.

PALM, B. T. 1922. Aanteekeninger
over Slijmziekte in Arachis
hypogaea (Katjang tanah). Inst v.
Plantenzidkten (Dutch Eastlndies).
Meded. 52, 41 pp. English

Bac-terial Wilt in solanaceous
crops grown in rice fields. In:
Proc. Planning Conference and
work-shop on the ecology and
control of bacterial wilt caused
by Pseudomonas solanacea-
rum. North Carolina State

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University. Raleigh, N.C., July
18-23, 1976.

SOHI, H. S., RAO, M. V. B., RAWAL,
R. D. and KISHUN, R. 1981.
Effect of crop rotations on bac-
terial wilt of tomato and eggplant.
Indian Journal of Agriculture
Science 8: 572-573.

TUNG, P. X. 1986. Bacterial Wilt in
Vietnam. In: Persley, G. J. (ed.).
Bacterial Wilt Disease in Asia and
the South Pacific. ACIAR Proceed-
ings 13, pp. 68-70, ACIAR,

WANG, J. S., X. Y. HOU and B. J. HU.
1983. Studies on the control of
the bacterial wilt of peanut. Acta
Phytophylactica Sinica. 10, 79-84.

ZEHR, E. I. 1969. Studies of the
distribution and economic impor-
tance of Pseudomonas solanacea-
rum E.F. Smith in certain crops in
the Philippines. Philipp. Agric. 53:

Philipp. Phytopathol. 1994, Vol. 30(2):100-110'



Part of the Corn Research and Outreach Program (CROP) at the University of
Southern Mindanao Agriculture Research Center (USMARC) and funded by the
SAID with counterparts from CIMMYT-DOST/PCARRD-DA/BAR-USM.

Respectively, Corn Breeder and Plant Pathologist, Crops Research Division,
USMARC, University of Southern Mindanao, Kabacan, Cotabato.

Key words: Breeding, corn, downy mildew, resistant variety


Three new high yielding and downy mildew resistant
open-pollinated corn varieties developed at University of
Southern Mindanao Agricultural Research Center (USMARC)
have been approved for commercial release or production by
the Philippine Seed Board (PSB) in August 1993. These were
USM Var 3 and USM Var 5 (yellow), and USM Var 10 (white)
with respective mean yields of 5.30, 6.80, and 4.47 t/ha
from PSB trials across locations in the country. These
varieties mature from 100 to 110 days, endosperms are
semi-flint to flint, plant height ranging from 206 to 232 cm,
days to silking, 54 to 55, and resistant to borer infestation.
Other special traits are: drought tolerant, adapted to acidic
soil, and low input variety (USM Var 3), very high yield (USM
Var 5), and shade tolerant (USM Var 10). Improvement
procedures employed S1 generation/ recombination followed
by half-sib ear-to-row and modified ear-to-row selection for 4
cycles and/or half-sib ear-to-row family selection for 8 cycles.
Genetic parent materials originated from CIMMYT and


Corn is one of the important cereal
crops in the Philippines and ranks
second to rice as a staple food of
Filipinos. Seventy percent is used as
main feed ingredient or supplement for
the livestock industries. Seven million
Filipinos depend on corn as a source of
income (Pamplona, 1993).

The national average yield of corn
in the Philippines is the lowest in Asia
(1.42 tons/ha). This is because more
than 80% of the corn farmers use the
traditional low yielding varieties.
Moreover, downy mildew (DM) caused
by Peronosclerospora philippinensis
(Weston) Shaw is long recognized as

Philipp. Phytopathol. 1994, Vol. 30(2):100-110

the most important disease of corn in
the country. It is so devastating that
yield loss due to this disease in
farmer's fields ranges from 15 to 40%
(Exconde, 1980). As a result, the
country does not produce enough corn
to meet the local demand. Corn
production therefore needs to be
increased. The government, through
the Department of Agriculture, has
initiated the Grains Production
Enhancement Program (GPEP)
advocating the use of high yielding
hybrids and open-pollinated varieties.
In response to the problem,
USMARC-USM, being the national
research center for corn, developed
new high yielding DM and borer
resistant open pollinated varieties
(OPVs) which were commercially
released by the Philippine Seed Board
(PSB) in August 1993). The sustained
development and improvement of new
corn varieties that are high yielding and
resistant to pests and diseases
therefore become more relevant and

The objectives of this study were
to develop new high yielding and
downy mildew/corn borer resistant
corn varieties and to further improve
the existing yellow and white corn
populations at USMARC-USM.


Breeding Methodologies and Screening
for DM Resistance

USMARC 1188. This variety was
originally extracted from CIMMYT's
Advanced Population 28 (Amarillo
Dentado) and improved at USMARC
using half-sib family selection (Fig. 1).
In an effort to further improve its yield
and resistance to downy mildew and
corn borer, 500 superior plants were
self-pollinated for recombination. At

Fig. 1. Isolated half-sib
crossing block.


harvest, 250 of the S1 families were

A set of 250 S1 families plus six
local checks were planted for progeny
yield trial (PYT) using 16 x 16 lattice
experimental design (Fig. 2) and
another set in the downy mildew
nursery. Remnant seeds of each
families were kept in cold storage

Using the remnant seeds, top ten
high yielding and DM resistant S1
families were recombined in a diallele
crossing system which produced 25 F1
crosses. To advance F1s to F2s, a
roughly equal number of seeds were
taken from each cross and mixed to
make the F1 bulk for planting and
advanced to F2. The F2 is now the
Improved CIMMYT Pop 28 (USMARC

500 ears

Crossing block

Before harvest

Selected 50% of the female rows

Select 2-4 ear/family

+ and 500 ears breeder's seeds

102 Philipp. Phytopathol. 1994, Vol. 30(2):100-110

Progeny Generation

Rem nant .... ............................. 250 S, line

............ :.= ............................. ..... .............,

DM PYT + 6 local checks
Nursery 1 6 x 16 lattice deisng


.......................... 10 high yielding DM ....
resistant S, lines
Diallele Crossing

F2 ................. .. ................ Improved version of
the variety

Fig. 2. Intrapopulation Improvement Scheme.

Philipp. Phytopathol. 1994, Vol. 30(2):100-110

USMARC 0190. This variety was
originated from the varietal cross
between CIMMYT's Suwan 1 C6 and
Pop 28 DMR. When first planted for
seed increase, this population was
observed to be susceptible to DM, had
variable plant and ear heights,
proliferated with elongated shank, and
most of the ears had exposed ear tips.
These characters were eliminated
through a strict selection method using
modified ear-to-row improvement
scheme. Four hundred half-sib families
were generated and subjected to DM

Strict selection was done during
vegetative stage up to brown husk
stage. Out of 400 families, 80
superior and DM-resistant families
were initially selected. During harvest
time, five good ears were taken from
each of the 80 families which
constituted 400 ears. The 400 ears
were used for the next cycle of
improvement. USMARC 0190 was
developed in four cycles of selection
wherein proliferation, elongated shank,
exposed ear tip, and variable height
were reduced to as low as 10% and in
both instances rated resistance to
downy mildew infection.

USMARC 1288. The variety was
extracted from CIMMYT's Pop 2. The
breeding procedure used in developing
this variety was similar to USMARC
0190 but development was completed
in eight cycles.

Procedure in Screening Corn Entries for
Resistance to DM

Spreader rows were planted two
weeks ahead of the test materials or
entries and inoculated with the fungus
seven days after planting (DAP). The
various test entries were planted in
three consecutive rows and alternated
.by the spreader rows. Standard

cultural practices were followed except
that no pesticides were applied.

Percentage infection was rated
weekly until about one month when
there was no more apparent increase
in downy mildew incidence. This was
computed based on the formula:

% Infection = (Plants Infected/
Total Plant Population) 100

The modified rating scale
recommended by the Technical
Working Group during the 1989
National Symposium-Workshop on
Evaluation of Host Plant Resistance to
Pathogens and Insect Pests of Corn
and Sorghum was followed, wherein:

1 25 % infection = Resistant
25 50 % infection = Intermediate
51 100 % infection = Susceptible


USM Var 3 (PSB Cn 93-31)

The USM Var 3 was entered as
USMARC 1188 in the PSB National
Cooperative Testing for Corn and
locally known as People's Yellow Corn.
Some characteristic features of this
variety are shown in Fig. 3 and Table
1. It is a yellow semi-flint, with strong
seedling vigor, uniform height,
relatively short plant (206 cm) and ear
heights (95 cm) and early maturing
(100 to 105 days). It has sturdy stalk
making it drought tolerant and highly
resistant to lodging. It is also resistant
to corn borer and DM. USM Var 3
yielded 5.65 t/ha across locations and
seasons (1989 to 1991) while IPB Var
1 (check) yielded 5.5 t/ha (Table 2).
This variety is also responsive to
fertilization (Table 3). In a field trial
conducted in Tupi, South Cotabato,
with 60-30-30 kg NPK/ha, USM Var 3

Philipp. Phytopathol. 1994, Vol. 30(2):100-110

Table 1. Description of Philippine Seed
varieties developed at USM.

Board newly released open-pollinated

Attribute USM Var 3 USM Var 5 USM Var 10


5.3 t/ha1

6.8 t/ha1

4.74 t/ha1

Local name




Ear height

Plant height

Days to silking

Weight of
1000 grains

Maturity period

Reaction to DM

Reaction to
corn borer

Special traits

People's Yellow


Half-sib family
selection for
8 cycles to
improve flint-
iness, reduce
height, improve
yield and
resistance to


95 cm

206 cm

55 DAP

305.78 g

100-105 days

(2.44% infection)


Drought tolerant
Also adaptable
in the acidic
soils; 4.8 pH
low input variety

Mindanao Yellow

Suwan 1 C6 x Pop

ear-to-row for
4 cycles to
resistance to
DM, improve
uniformity of
the plant height
& increase yield

Semi-flint to

121 cm

232 cm

56 DAP

387.87 g

100-110 days

(4.41 % infection)

Resistant (2.60%
infection Wet

Very high yield

Cotabato Mighty


Half-sib and
family select-
ion for 8
cycles; to
reduce height,
improve yield
and resistance
to DM


98 cm

206 cm

54 DAP

302.90 g

100-110 days

(6.67% infection)


Shade tolerant

1Consolidated yield data from UNCT-PSB trials.

Philipp. Phytopathol. 1994, Vol. 30(2):100-110

Table 2. Summary yield (t/ha) performance of USMARC 1188 and IPB Var 1 across

USMARC 1188 IPB Var 1
LOCATION -------------------------------------------MEAN -------------------------------------MEAN
1989 1990 1990-91 1991 1989-90 1990 1990-91 1991

UPLB 6.45 4.4 5.4 5.23 5.37 5.63 4.44 5.58 4.82 5.11
ILAGAN 6.52 C 5.58 6.65 6.25 5.26 C 5.35 6.61 5.74
BATAC 6.66 B 4.68 A 5.67 5.90 B 4.67 A 5.28
PILl 4.68 C E 4.97 4.82 3.77 C E 3.82 3.79

VISCA 5.76 C 6.19 C 5.97 4.88 C 6.40
MANDAUE A C 4.70 6.72 5.71 A C 7.80 5.99 6.49
UBAY 2.92 C 4.73 7.73 6.23 3.61 C 3.91 9.52 5.93

TUPI 3.61 A 3.48 A 3.54 3.82 A 4.08 A 3.95
USM 6.21 5.36 4.27 7.32 5.79 4.65 5.42 4.82 6.48 5.32
CMU 3.02 6.10 6.83 A 5.31. 3.50 5.42 6.26 A 5.06
IPIL 6.18 C 3.39 C 4.78 5.78 C 5.09 5.43
MEAN 5.33 5.39 5.46 6.44 5.65 5.18 5.45 5.52 5.87 5.58
No. of Test 10 3 10 6 29 10 3 10 6 29

1A = cv 20.99%; B = Location not included in trial; C = entry not tested in this location; D = Data
omitted due to overall poor stand in the location; E = Yield of check is below 3 tons/ha.

Table 3. Yield (t/ha) of four corn varieties as affected by three levels of fertilizer.

0-0-0 60-30-30 120-60-60

USM Var 1 4.45 de 5.25 cd 5.85 bc

USM Var 3
(USMARC 1188) 4.72 de 4.82 de 5.05 de

USM Var 5
(USMARC 0190) 4.65 de 6.20 ab 6.80 a

IPB Var 1 (check) 4.38 cd 5.25 cd 6.20 ab

1 Means followed by the same letter are not significantly different at 5% level of significance, DMRT.

yielded 5.31 t/ha, an increase of 0.5
t/ha over IPB Var 1 (Table 4;. USM
Var 3 is also adaptable in acidic soil
(pH of 4.8) with a mean yield of 5.42
t/ha compared to the IPB Var 1 (check)
that yielded 4.94 t/ha (Table 5).

USM Var 5 (PSB Cn 93-32)

USM Var 3, entered as USMARC
0190 in the PSB NCTC and with local
name as Mindanao Yellow Eagle, is a
yellow semi-dent to flint (Fig. 4). It
has vigorous seedling stand with big
sturdy stalks making it resistant to
lodging. It is resistant to downy
mildew (4.41% infection) and corn
borer (2.60%). Besides, it has medium
ear and plant heights (121 and 232
cm, respectively) and matures in 100
to 110 days (Table 1). During the
UNCT-PSB trials, this variety yielded
6.8 t/ha compared to IPB Var 1, IPB
Var 2, and P3228 (a hybrid) with
yields of 5.17, 5.28 and 6.33, (Table
6). Furthermore, USM Var 5's mean
yield across locations and seasons,
1991-92, was 6.45 t/ha compared to
IPB Var 1's 5.67 t/ha (Table 7). In a

Philipp. Phytopathol. 1994, Vol. 30(2):100-110

fertilizer trial at USMARC, USM Var 5
outyielded other entries in all NPK rates
of 0-0-0, 60-30-30 and 120-60-60
(Table 8). In Tupi, South Cotabato,
USM Var 5 yielded 6.35 t/ha compared
to IPB Var 1's 4.86 t/ha (check) when
applied with NPK of 60-30-30 kg/ha
(Table 6).

USM Var 10 (PSB Cn 93-27)

USM Var 10, also entered as
USMARC 1288 in the PSB-NCTC and
locally named as Cotabato' Mighty
White, is a white flint, matures in 100
to 110 days, medium height (202 cm)
and resistant to downy mildew and
borer. infestation (Table 1). It has
robust seedlings and responsive to
high fertilizer. It can also grow in
acidic soil (4.8 pH) and with an
average yield of 5.52 t/ha (Table 5).
One important characteristics is its
shade tolerance (Table 9). When
planted under 12 year-old coconut
trees with approximately 40% shading,
USM Var 10 outyielded two other
OPVS with an average yield of 2.18

Table 4. Comparative yield of three USM open-pollinated varieties evaluated at Tupi,
South Cotabato at fertilizer rate of 60-30-30 kg NPK/ha in 1991.

(t/ha) (t/ha)

1. USMARC 1188 (USM Var 3) 5.31 0.50

2. USMARC 0190 (USM Var 5) 6.35 1.49

3. USMARC 0191 5.22 0.36

4. USM Var 1 (ck) 4.95 0.09

5. IPB Var 1 4.86

Philipp. Phytopathol. 1994, Vol. 30(2):100-110 107

Table 5. Yield (t/ha) of two USM open-pollinated varieties grown in acidic soil of

IPB Var 1
SEASON USMARC 1188 USMARC 1288 (check)

1990 WS 6.10 5.77 5.44

1990-91 DS 6.83 7.18 6.26

1991 WS 3.32 3.60 3.12
MEAN 5.42 5.52 4.94

Table 6. Comparative yield of USM Var 5, hybrid, and PSB released USM varieties.


USM Var 5 6.80 23.70

P3228 Hybrids (ck) 6.33

IPB Var 1 (ck) 5.17

IPB Var 2 (ck) 5.28.

USM Var 2 6.35 16.85

USM Var 4 5.87 10.05

USM Var 6 5.94 11.11

USM Var 8 6.00 12.00

USM Var 1 6.25 15.52

1Yield data from UNCT PSB trials.

Philipp. Phytopathol. 1994, Vol. 30(2):100-110

Fig. 3 USM Var 3 (USMARC 1188)
PSB Variety Code: PSB Cn 93-
31; Local Name: Peoples
Yellow Corn; Date Released by
PSB: August 1993

Fig. 4. USM Var 5 (USMARC 0190);
PSB Variety Code: PSB Cn 93-
32; Local Name: Mindanao
Yellow Eagle; Date Released by
PSB: August 1993

Table 7. Summary yield (t/ha) of USM Var 5 across location and season.

USMARC 01901 IPB Var 1
1991 1991-92 1991 1992

UPLB 5.49 6.58 6.03 4.82 5.56 5.19
ILAGAN 7.03 9.10 8.06 6.61 7.87 7.24
BATAC 6.28 6.28 6.13 6.13
PILI 4.21 3.90 4.05 3.82 3.40 3.61

MANDAUE 6.67 4.81 5.74 5.47 5.63 5.55
UBAY 7.99 7.99 7.38 7.38

USM 6.97 6.97 6.40 6.40
CMU 7.88 7.88 -5.94 5.94
IPIL 6.71 6.71 4.94 4.94

MEAN 6.43 6.47 6.45 5.72 5.62 5.67
No. of Test 6 7 13 6 7 13

Philipp. Phytopathol. 1994, Vol. 30(2):100-110 109

Table 8. Comparative yield (t/ha) of USM open-pollinated varieties at three fertilizer
levels (USM, 1992).

HYBRID 0 0 0 60-30-30 120-60-60

1. Red-cobbed Tiniguib 2.64 3.51 4.16

2. USM Var 2 3.41 4.39 5.03

3. USM Var 4 3.42 4.13 4.83

4. USM Var 3 3.42 4.44 5.31

5. USM Var 5 3.61 4.77 5.52

6. P3228 3.50 4.33 5.49

1Average of four experiments in South and North Cotabato.

Table 9. Yield of three corn varieties planted under 12-year-old coconut trees with
40% shading in Aringay, Kabacan, Cotabato, Oct. 1992 Feb. 1993.

VARIETY (t/ha) PER 100 g

USM Var 6 2.04 b 326.91 b

USM Var 10 2.18 a 325.25 c

USM Var 2 1.65 c 394.56 a

1 Means followed by the same letter are not significantly different at 5% level of significance, DMRT.

Fig. 5. USM Var 10 (USMARC 1188)
PSB Variety Code: PSB Cn
93-27 Local Name: Cotabato
Mighty White Date Released
by PSB: August 1993.


ALEJANDRO, F.R. 1993. New high
yielding USM corn varieties, 2nd
CEMARRDEC Techno-Commercia-
lization Fora, R & D Highlights and
Planning Workshop, July 26-28,
1993, USM, Kabacan, Cotabato
(Mimeog. Report), 17 p.

ALEJANDRO, F.R.. 1994. Develop-
ment/Maintenance and seed
multiplication of OPV and hybrids.
USM R & E Review and Planning
Workshop, January 25-27, 1994,
USM, Kabacan, Cotabato
(Mimeog. Report), 15 p.

Philipp. Phytopathol. 1994, Vol. 30(2):100-110

EXCONDE, O.R. 1980. Corn diseases
and their control. Proceedings of
the Symposium on Philippine Phy-
topathology 1917-1977, UPLB,
College, Laguna, pp. 98-106.

PAMPLONA, P.P. 1992. The success-
ful implementation of the Corn
Research and Outreach Program
(CROP) in USM as a model in the
conduct of national R & D
programs (Terminal Report), 138

PAMPLONA, P.P. 1993. High yielding
corn varieties and hybrids.
Technology 25 (2): 19.

RAYMUNDO, A.D. 1989. Evaluation
techniques for Philippine corn
downy mildew. Paper presented
during the National Sympo-
sium-Workshop on Evaluation of
Host Plant Resistance to
Pathogens and Insect Pests of
Corn and Sorghum, July 20-21,
1989, USMARC-USM, Kabacan,

1994. Identification of promising
lines, inbreds, and hybrids to
Philippine corn downy mildew and
corn borer. USM R & E Review
and Planning Workshop, January
25-27, 1994, USM, Kabacan,
Cotabato (Mimeog. Report), 12 p.


The authors express their
profound thanks and gratitude to Dr.
P.P. Pamplona, Program Leader of the
CROP at USM for kind courtesies given
them during the conduct of the

Philipp. Phytopathol. 1994, Vol. 30(2):111-117



Part of the Ph.D. thesis of the senior author.

Respectively, University Researcher, Institute of Plant Breeding and Emeritus
Professor, Department of Plant Pathology, University of the Philippines at Los Banios,
College, Laguna, Philippines.

Key words: Botryodiplodia theobromae, control, host range, salago, stem
rot, survival, Wikstroemia lanceolata.


Botryodiplodia theobromae survived longer in diseased
tissue and in yeast extract agar than in sterile soil.

B. theobromae induced disease on atis, citrus, papaya,
jackfruit, cassava, cotton, mungbean, cacao, banana, cowpea
and corn but not on gabi and sweet potato. All of the salago
species tested were susceptible to stem rot.

Benomyl, thiophanate methyl, captain, mancozeb and
maneb were effective in suppressing the mycelial growth of
B. theobromae in culture and in protecting salago plants from
infection. None of the fungicides used caused complete arrest
of the fungus when applied as eradicant.


Stem rot is becoming a serious
disease of salago, a promising export
fiber crop. The etiology of the disease
was studied in detail by Dizon (1991).
The causal fungus, Botryodiplodia
theobromae Pat., is one of the
common fungal pathogens causing
diseases on many crops. It is
considered a weak parasite that
invades its host only through wounds
or necrotic tissues (Wardlaw, 1932;
Stevens, 1941; Goos et al., 1961).

The fungus has been isolated from soil
(Farrow, 1954) and air (Meredith,
1961) and produced chlamydospores
as means of survival in cultures (Goos
et al., 1961; Satour et al., 1969).

As salago gains popularity as a
potential export fiber crop, reliable and
efficient disease management
strategies must be sought in order to
assure foreign buyers of our capacity
to deliver the needed quantity and
quality of fibers and be competitive in
the world market in the near future.

Since very little information is
available in the Philippines about
salago stem rot and its associated
pathogen, this study was conducted to
determine the mode of survival and
host range of the pathogen and to
screen fungicides against the disease.


Survival of B. theobromae

Longevity in Diseased Tissue.
Survival of B. theobromae in diseased
tissues was studied under three
conditions. In the first treatment,
stems heavily infected with stem rot
were cut into short lengths, placed in
plastic bag and kept in the laboratory
under ordinary room temperature (27-
30 C). In the second treatment, intact
infected stems were left in the
greenhouse for the entire duration of
the experiment. For the third
treatment, infected stems were cut
into short lengths, placed in
Erlenmeyer flasks containing sterile soil
and kept in the laboratory at 27-30 C.

Pathogen survival in each
treatment was manifested at biweekly
intervals by scraping the pycnidia from
the epidermis of infected stem using
flame-sterilized scalpel and placing
them on freshly prepared yeast extract
agar (YEA) plates. The plates were
observed for the growth of B.
theobromae. The procedure was
continued until there was no more
growth of the fungus on the YEA

Longevity in Culture. Survival of
B. theobromae in pure culture was
determined in YEA slant and in sterile
soil. Mycelial bits together with the
pycnidia from the stock culture were
plated at biweekly interval to freshly
prepared YEA and observed for
mycelial growth until 7 days. The

Philipp. Phytopathol. 1994, Vol. 30(2):111-117

procedure was continued until no
mycelial growth was observed.

Mycelia and pycnidi, from 14 day-
old YEA plates were mixed with
sterilized soil placed in Erlenmeyer flask
and incubated at the laboratory at 27-
30 C. Bits of the soil were transferred
to YEA plate and observed for mycelial
growth until 7 days. This procedure
was continued until no more growth of
the fungus was observed,

Host Range

of Botryodiplodia

Reaction of Salago Species. Newly
harvested seeds of four species of
salago, namely, W. lanceolata, W,
ovata, W. indica and W. meyeniana
collected from albay, Cebu and Leyte
were sown in seedboxes containing
baked soil. After one month, seedlings
were transferred to No. 7 clay pots
containing baked soil and maintained in
the greenhouse. Six months after
transplanting, 20 plants per species
were inoculated using the wound
inoculation method with 7-mm
diameter one week-old mycelial agar
disc as inoculum. Disease incidence
was evaluated 20 days after
inoculation. Disease reaction was
determined using disease rating scale

Percent Infect




Highly Resistant (HR)
Resistant (R)
Moderately Susceptible (MS)
Susceptible (S)
Highly Susceptible (HS)

Reaction of Other Crop Species.
Seeds of various crop species were
sown in seedboxes or pots with baked
soil and the plants were maintained in
the greenhouse. Test plants were
inoculated with culture of B.
theobromae mycelial agar discs, placed

Philipp. Phytopathol. 1994, Vol. 30(2):111-117

at the injured portion of the tissue and
held in place by masking tape. Healthy
fruits, pods and tubers, was surface
disinfected, placed individually in clean
plastic bag, inoculated, incubated in
the laboratory at 27-30 C and
observed for symptom development.

Fungicide Evaluation Against Stem Rot

Nine commercial fungicides,
namely, benomyl, mancozeb,
chlorothalonil, propanocarb, captain,
thiophanate methyl, PCNB, maneb and
copper, were evaluated against stem
rot of salago. They were initially
assayed in the laboratory by paper disc
method using four concentrations
including manufacturer's recommended
rates. Effectiveness of the fungicides
was based on the diameter of mycelial
growth inhibition zones. Promising
fungicides were further tested in the
greenhouse using artificially inoculated
9-month old salago plants to determine
their protective and eradicative actions.
Effectiveness was based on disease
incidence and severity.


Survival of B. theobromae

Botryodiplodia theobromae
survived longer in diseased stem
tissues stored in plastic bag (398 days)
and then in artificial medium (341.
days) (Table 1). The fungus survived
for 216 days in intact stem tissues and
204 days in sterile soil.

The pathogen poorly survived in
diseased stem tissues mixed in sterile
soil. Longer survival of the fungus in

diseased stem tissues either intact or
stored in plastic bag can be attributed
to the presence of thick-walled mature
pycnidiospores which are resistant to
desiccation. The development of
secondary wall was not observed in
unmature spores. The same survival
structure was observed in Diplodia
species (Walker, 1930; Brown, 1971).
The persistence of the pathogen in
artificial medium can also be attributed
not only to'the formation of mature
pycnidiospores, but also to the
formation of chlamydospores. The poor
survival of the pathogen in diseased
stem tissues incorporated in sterile soil
was primarily due to the actions of
opportunistic organisms such as
Aspergillus spp. and Penicillium spp.
that were present in the stem tissues.
This suggests that the pathogen is a
poor soil competitor.

Table 1. Longevity of Botryodiplodia
theobromae isolated from
salago under laboratory


Diseased Tissue
Stored in plastic bag 398
Intact tissue1 216

Artificial Medium
Yeast Extract Agar 341

Sterile Soil
Mycelia and pycnidia 204

Diseased stem tissues 141

'Maintained in the screenhouse.

Host Range of B. theobromae

All species of salago, namely,
W. lanceolata, W. ovata, W. indica and
W. meyeniana were infected with B.
theobromae (Table 2). All species
showed high degree of susceptibility.
Infected plants wilted 24 hr after
inoculation. The wilting symptom may
be attributed to toxin causing
ultrastructural abnormalities on the
conducting tissues. Numerous workers
(Goos et al., 1961; Satour et al.,
1969; Mullen, 1987; Dizon, 1991)
reported the production of red
pigment, possibly toxin, when the
fungus was grown in either liquid or
solid medium. However, its role in the
pathogenesis in salago has not been
thoroughly elucidated.

With the exception of Colocasia
esculenta and Ipomoea batatas, all test
plants were infected after inoculation
with B. theobromae (Table 3). The
fungus produced black mycelia on
inoculated tissues. Inoculated banana,
papaya, mango and cassava showed
characteristics water-soaking and
rotting symptoms with yellow
exudates oozing out from rotted
tissues. This suggests the. involvement
of macerating or tissue degrading
enzymes. Arinze and Smith (1979)
reported that B. theobromae produced
pectolytic enzymes, polygalactunorase
complex, that dissolve the middle
lamella causing collapse of cells when
inoculated to susceptible sweet potato
cultivar. In addition, it is possible that
the toxin produced by the fungus could
have altered the permeability of the cell
membrane causing leakage of yellow
exudate. The same fungus was

Philipp. Phytopathol. 1994, Vol. 30(2):111-117

isolated from the diseased tissues of
the test crops.

The fungus failed to infect sweet
potato contrary to the report of Arinze
and Smith (1979). Possibly, this
'particular variety is resistant to
B. theobromae.

Fungicide Evaluation Against Stem Rot

Seven out of nine fungicides
showed biological activity on
B. theobromae (Table 4). Benomyl
consistently produced the largest
growth inhibition zone diameter in all
the fungicide rates except in the
manufacturer's recommended rate.
Thiophanate methyl ranked second in
effectiveness followed by captain,
mancozeb, maneb and chlorothalonil..
Copper fungicide showed.activity only
when the manufacturer's
recommended rate was used while
PCNB and propamocarb did not show
any biological activity against B.

Six promising fungicides, namely,
benomyl, maneb, thiophanate methyl,
captain and mancozeb were further
tested under greenhouse condition.
These were very effective against stem
rot as protectant fungicides, but failed
to exhibit effectiveness as eradicant
(Table 5). Results suggested that stem
rot of salago can be effectively
managed by protecting healthy salago
plants with fungicides. Since fungicide
control is becoming more expensive,
future studies should focus on other
control measures that are environment
friendly and more economical to use.

Philipp. Phytopathol. 1994, Vol. 30(2):111-117

Table 2. Reaction of Wikstroemia species against stem rot three weeks after
inoculation with Botryodiplodia theobromae.


Albay W. lanceolata 100 HS
W. ovata 100 HS

Cebu W. indica 100 HS
W. lanceolata 100 HS
W. meyeniana 100 HS
W. ovata 70 HS

Leyte W. ovata 100 HS

1Mean of two replications, 20 plants per replicate.
HS = "ighly Susceptible (51 to 100% infection).

Table 3. Reaction of the different crop species to wound inoculation of
Botryodiplodia theobromae at laboratory conditions.


Atis Annona squamosa fruit, ripe +
fruit, unripe +

Banana Musa paradisiaca Saba fruit, ripe +
Latundan fruit, ripe +
Lakatan fruit, ripe +

Cacao Theobromae cacao pod +

Cassava Manihot esculenta Lakan tuber +

Citrus Citrus sp. Lado fruit, ripe +
stem +
Corn Zea mays CRPR-1 kernel +

Cotton Gossypium hirsutum Deltapine boll +
Cowpea Vigna sinensis 14-4 seed +

Jackfruit Artocarpus heterophyllus fruit, ripe +

Mango Mangifera indica Carabao fruit, ripe +

Mungbean Phaseolus vulgaris Pag-asa 3 pod +

Papaya Carica papaya fruit +

Gabi Colocasia esculenta tuber

Sweet potato Ipomoea batatas V20-429 tuber

1Symbol: + = positive infection; = negative infection; Banana, cassava, jackfruit, mango and
papaya exhibited water-soaking and rotting symptoms with yellow exuidates oozing out from infected

116 Philipp. Phytopathol. 1994, Vol. 30(2):111-117

Table 4. Bioassay of fungicides against Botryodiplodia theobromae using paper disc



Thiophanate methyl









INHIBITION ZONE (Diameter in mm)1
500 ppm 1000 ppm 15000 ppm

29.5 30.3 37.2

28.0 28.4 30.1

17.9 25.0 25.8

13.2 12.8 17.6

10.0 11.1 15.2

9.0 8.2 10.0

0 0 0

0 0 0

0 0 0

0 0 0











I'Mean of four replications; measurements taken 48 hr after plating.

2Benomyl, 1000 ppm; thiophanaie methyl, 1430 ppm; captain, 6250 ppm; mancozeb, 4690 ppm;
maneb, 2500 ppm; chlorothalonil, 5000 ppm; copper, 23210 ppm; PCNB, 2000 ppm, and propamocarb,
5710 ppm.

Table 5. Efficacy of fungicides at 1500
control of stem rot in salago.1


ppm as protectant and eradicant for the

-----Protectant Eradicant----
Protectant Eradicant

Benomyl 100 24

Maneb 100 18.9

Thiophanate methyl 100 17.4

Captan 100 3.5

Mancozeb 98 1.8

1Taken 14 days after application of fungicide.

Philipp. Phytopathol. 1994, Vol. 30(2):111-117


ARINZE, A.E. and L.M. SMITH. 1979.
Production of polygalacturonase
complex of Botryodiplodia
theobromae and its involvement in
rot of sweet potato. Physical. PI.
Pathol. 17: 145-155.

BROWN, G.I. 1971. Pycnidial release
and survival of Diplodia natalensis
P. Evans spores. Phytopathology
61: 559-561.

DIZON, TEODORA O. 1991. Etiology
and chemical control of stem rot
of salago (Wikstroemia lanceolata
L.) and the survival and host range
of its pathogen. Ph.D.
Dissertation, UP at Los Ba$os,
College, Laguna. 113 p.

FARROW, W.M. 1954. Tropical soil
fungi. Mycologia 46: 632-646.

GOOS, R.D., E.A. COX and G.
STOTZKY. 1961. Botryodiplodia
theobromae and its association
with Musa species. Mycologia 53:

MEREDITH, O.S. 1961. Botryodiplodia
theobromae Pat. and Nigrospora

sp. in the air of a Jamaican
banana plantation. Nature 190:

MULLEN, J.M. 1987. Dugwood
(Cornus florida) trunk canker,
Botryodiplodia theobromae, a
stress pathogen of dugwood.
Phytopathology 77: 1733.

W.B. HEWITT. 1969. Studies on
Diplodia and Diplodia-like fungi. I.
Effect of carbon source on certain
taxonomic characteristics and on
growth in agar culture. Hildardia
39: 601-629.

STEVENS, N.E. 1941. Host relation in
species of Diplodia and similar
genera. Mycologia 33: 69-73.

WALKER, M.N. 1930. Cotton diseases
in Florida. Fla. Agr. Expt. Sta. Bull.
214 p.

WARDLAW, C.W. 1932. Observations
on the pycnidium of
Botryodiplodia theobromae Pat.
Ann. Bot. 46: 229-238.

Philipp. Phytopathol. 1994, Vol. 30(2):118-121



Portion of the undergraduate thesis of the first author.

Respectively, former student and Professor, Department of Crop Protection
(Plant Pathology), College of Agriculture, University of Southern Mindanao, Kabacan,

Key words: Curvularia lunata, etiology, Fusarium moniliforme, kalachuchi,
Plumeria acuminata.


Two fungal foliar diseases attacking kalachuchi (Plumeria
acuminata) singly or simultaneously are heretofore reported
for the first time. Curvularia lunata and Fusarium moniliforme
caused leaf spot and leaf blight diseases, respectively.
Pathogenicity tests revealed that characteristic leaf spot
symptom developed on healthy kalachuchi leaves 15 days
after inoculation with C. lunata while leaf blight symptom
developed nine days after inoculation with F. moniliforme.


Kalachuchi (P/umeria acuminata
Ait.) of the family Apocynaceae is
known in India and Sri Lanka as a
sacred tree and planted mainly around
temples. In Malaysia and China, it is
usually cultivated in cemeteries and
thus called graveyard tree. In the
Philippines, it is a popular landscape or
ornamental tree on gardens, parks,
buildings, and residential houses.

Frangipani or Plumeria as this tree
is sometimes called is very picturesque
with stout branches and a broad
crown. The flowers (in varietal pink,
red, yellow, or white colors) are
attractive, pleasantly fragrant and
commonly strung together as leis.

Tangonar, and Quebral (1992)
reported two diseases of kalachuchi in
the Philippines: leaf spot caused by
Cercospora plumeriae discovered by
Quimio and Abilay (1977) and sooty
mold caused by Conidiocarpus sp.
discovered by Kriengyakul and Quimio
(1983). This study aimed to determine
the etiology of two new leaf diseases
attacking kalachuchi in the campus and
vicinities of the University of Southern
Mindanao at Kabacan, Cotabato.


Collection of Diseased Kalachuchi
Leaves. Infected leaf samples were
collected from trees in different areas
of the University campus and vicinities,

Philipp. Phytopathol. 1994, Vol. 30(2):118-121

placed in clean plastic bags, and
brought to the laboratory for diagnosis.
Initial microscopic examinations
showed the presence of fungal
structures on newly prepared slide

Preparation of Culture Medium.
Potato sucrose agar (PSA; 15 g table
sugar, 200 g potato, 20 g agar, and
1000 ml distilled water) was prepared
by following standard procedure. Flat
bottles were each filled with 10 ml
PSA, plugged with cotton, and
autoclaved for 20 min at 15 psi.

Isolation of the Suspected Patho-
gens. Infected leaves of kalachuchi
were washed and sections from the
advancing lesions were planted equi-
distantly on PSA and incubated upside
down at room temperature. Once
growth was observed, isolations into
pure cultures of individual isolates in
previously plated flat bottles were

Pathogenicity Tests. Pure cultures
of the individual fungal isolates were
used as inocula by spraying the spore
suspensions (40,000 spores/ml) onto
healthy leaves of kalachuchi cuttings
previously grown in pots (size 36).
Following Koch's postulates, reisola-
tions of the fungal organisms were
done to confirm that they are the
causal agents of these diseases.

Identification of the Fungal Iso-
lates. The pathogens were identified
based on pathogenicity tests and mor-
phological characteristics of the iso-
lates. Slide mounts were prepared
from both freshly collected diseased
specimens and pure cultures, stained
with methylene blue and examined in a
compound microscope. Twenty-five
randomly selected conidia were


Symptomatology. The two foliar
diseases of kalachuchi found in the
University of Southern Mindanao
campus and vicinity were leaf spot and
leaf blight. The spots are characterized
by circular to irregularly shaped lesions
scattered on the leaf surface which
were reddish to dark brown in color.
The lesions seldon coalesce but
affected parts become necrotic (Fig.
1). Curvularia sp. was constantly
associated with the leaf spot symptom.
In the case of leaf blight, the lesions
were light brown in color and
sometimes water-soaked in appearance
as they mature. In advanced stages,
the center of the lesions turn grayish
or straw-colored and the affected
tissues dry up (Fig. 2). Fusarium sp.
was constantly associated with the
blight symptoms upon microscopic

Pathogenicity Tests. Typical leaf
spot symptoms developed on
kalachuchi leaves 15 days after
inoculations with the Curvularia
isolates. It took only 9 days for the
Fusarium isolate to develop typical
blight symptoms on kalachuchi leaves.
The two fungal pathogens were
reisolated from the respective
artificially inoculated plants.

Morphological Descriptions of the
Fungal Pathogens. The Curvularia
isolate grew abundantly on PSA and
turned cottonly black with time.
Conidia obtained from PSA cultures
and infected leaf tissues were slightly
curved, dark brown in color, with three
septations, and measured 24.36 x
9.99 u (Fig. 3). Conidiophores were
brown, simple, and branched.

Philipp. Phytopathol. 1994, Vol. 30(2):118-121

Fig. 1. Leaf spot disease of kalachuchi
naturally infected by Curvularia
lunata showing circular lesions
all over the leaf blade.

The Fusarium isolate also. grew
abundantly on PSA. Fungal growth
appeared cottony and whitish to
yellowish in color. When examined
microscopically, the macroconidia were
hyaline and typically canoe-shaped,
with three septations and with average
measurements of 33.95 x 5.35 u (Fig.
4). Microconidia were unicellular. The
two fungal pathogens were
characterized morphologically following
the descriptions of Barnett and Hunter
(1972), Booth (1977), and Quimio

Based on pathogenicity tests and
morphological characteristics, the
fungal pathogen associated with the
leaf spot symptom is identified as
Curvularia lunata while the leaf blight
pathogen is identified as Fusarium

Fig. 2. Leaf blight of kalachuchi
naturally infected by Fusarium

Fig. 3. Conidia of Curvularia lunata
causing leaf spot disease of

Philipp. Phytopathol. 1994, Vol. 30(2):118-121


1972. Illustrated Genera of
Imperfect Fungi. 3rd Ed., Burgess
Publishing Co., Minneapolis,
Minnesota, 241 pp.

Laboratory g
identification of
CMI, UK, 58 p.

977.. Fusarium:
juide to the
the major species.

1983. Additional sooty molds in
the Philippines. in: Host Index of
Plant Diseases in the Philippines,
2nd Ed., 273 p.

QUIMIO, T.H. 1983.
and species
92, 88 p.

Illustrated genera
of Philippine
fungi. Bull. No.


Fig. 4. Conidia of Fusarium
moniliforme causing leaf blight
disease of kalachuchi.

QUIMIO, T.H. and L.E. ABILAY. 1977.
Unreported species of Cercospora
in the Philippines. In Host Index
of Plant Diseases in the
Philippines, 2nd Ed., 273 p.

1992. Host index of plant
diseases in the Philippines, 2nd
Ed., 273 p.

Philipp. Phytopathol. 1994, Vol. 30(2): 122-143

MAY 3-6, 1994

Control of Citrus Tristeza Closterovirus
in Pummelo By Cross Protection. L.E.
Herradura, N.B. Bajet, L.V. Magnaye.
DNCRDC, BPI, Davao City and UPLB,
College, Laguna.

Isolates of citrus tristeza clostero-
virus (CTV) collected from various
citrus plantations in Davao and
Batangas induced wide range of
symptoms and severity on different
citrus cultivars.These isolates were
free of citrus greening and exocortis
pathogens when subjected to biological
indexing. Enzyme-linked immunosor-
bent assay (ELISA) test confirmed the
isolates as CTV. On key lime (Citrus
aurantifolia) as indicator host, the
isolates were classified into mild and
severe strains. Mild strain exhibited
mild vein clearing while severe strain
caused severe vein clearing and stem
pitting. The isolates did not induce any
symptom on the leaves and stems of
sour orange (C. aurantium) that serve
as indicator host. Extracts of the mild
and severe strains reacted to the
monoclonal antibodies of CTV dwarf
strain (CTV-D).

Pummelo plants cv. Magallanes
pre-inoculated with mild strain
(pummelo 169) did not show any
severe symptom five months after
challenge inoculation by the severe
strains, pummelo P-03 and pummelo
AT. Similar pummelo cultivars
inoculated with the severe strains but
without preinoculation with the mild
strain showed severe symptoms. This
provided additional evidence for the
presence of CTV strains in the country.
The study also demonstrated that
cross protection can be a viable
alternative control for CTV in

Local Papers as Substitute for
Nitrocellulose Membrane in the
Detection of Bacterial Wilt Latent
Infection of Potato. J.S. Mariano,
J.DG. Dar and T.M. Lorezco. BNDRC,
BPI, Baguio City.

Eight locally produced papers
were evaluated as possible substitute
for the expensive and imported
nitrocellulose membrane. NCM-ELISA,
a diagnostic method developed by CIP,
Lima, Peru to detect the presence of
Pseudomonas solanacearum was used
in the study.

Among the tested materials,
cactus xerox paper, ordinary xerox
paper and vernal mimeographing paper
(substance 20) gave promising results.
The purple coloration on the papers
which corresponded to positive result
were comparable or similar to that of
the nitrocellulose membrane. The
antisera for the test could be recycled
or re-utilized once.

Test results showed that 38.63%
of the tubers of plants adjacent to
bacterial wilt-infected hills were
latently infected with P. solanacearum.

Isolation and Purification of the
Coconut Cadang-cadang Viroid
(CCCVd) for Analytical, Biological and
Molecular Characterization. Ma. Judith
B. Rodriguez and Ma. Teresa I. Namia.
PCA, Albay.

Several isolation procedures for
CCCVd that differ mainly by varying
the extraction buffer, nucleic acid
precipitant and deproteinizing agent to
suit the type of tissues used are
described. The degree of purity as

Philipp. Phytopathol. 1994, Vol. 30(2): 122-143

determined by the number of steps
depended on the purpose of isolating
the viroid. For routine rapid indexing of
CCCVd, two to three steps were
favored. However, for biological and
molecular characterization, relatively
pure isolates were essential.
Conditions to minimize viroid
degradation in vivo and in vitro were
also determined.

USM Var 3, USM Var 5 and USM Var
10: New High Yielding and Downy
Mildew Resistant Corn Varieties
Developed at USM, Kabacan,
Cotabato. F.R. Alejandro, N.G.
Tangonan and P.P. Pamplona. USM,
Kabacan, Cotabato.

Three new high yielding and
downy mildew resistant open-
pollinated corn varieties developed at
University of Southern Mindanao
Agricultural Research Center
(USMARC) have been approved for
commercial release or production by
the PhilFppine Seed Board (PSB) in
August 1993. These are USM Var 3,
USM Var 5 (yellow) and USM Var 10
(White) with respective mean yields of
5.30, 6.80 and 4.47 t/ha from PSB
trials across locations and seasons in
the country. These open-pollinated
varieties (OPVs) mature from 100 to
110 days, endosperms are semi-flint to
flint, plant height rang.,ig from 206 to
232 cm, days to silking, 54 to 55, and
resistant to borer infestation. Other
special traits are: drought tolerance,
adaptability to acidic soil, requires low
input (USM Var 3), high yield (USM
Var 5), and shade tolerance (USM Var
10). Improvement procedures em-
ployed S1 generation/recombination
followed by half-sib ear-to-row
selection for 8 cycles and modified ear-
to-row for 4 cycles and/or half-sib ear-
to-row family selection for 8 cycles.
Genetic parent materials originated
from CIMMYT and Thailand.

Trichoderma sp. for the Biocontrol of
Sweet Pepper Stem Rot (Sclerotium
rolfsii Sacc.). R.A. Paningbatan.
ViSCA, Baybay, Leyte.

Ten fungal isolates were
bioassayed against sweet pepper stem
rot pathogen Sclerotium rolfsii, and the
most antagonistic isolate (Trichoderma
sp.) was assessed for biocontrol
efficacy in the screenhouse and field
conditions. Trichoderma isolate (P-1)
from a soil sample of peanut field lysed
mycelia of S. rolfsii at the rate of 3.86
mm/day. It yielded 4 x 109
conidia/gram of dried taro tuber, 16.4
times higher than in rice bran. The
conidia/peso ratio of taro tuber was 36
times better than potato dextrose agar
and three times better thyn rice bran.
Seed treatment with 10 conidia/ml
provided 80.78% biocontrol efficacy;
76.5 and 73.04% for seedling dip
method under greenhouse and field
conditions, respectively. The control
efficacy of the isolate was comparable
to the level of protection of maneb
applied as drench. Sweet pepper plants
grown in plots with 72.23% disease
incidence yielded 1.89 tons/ha of fresh
fruits while seedlings protected with
Trichoderma sp. yielded 7.51 tons/ha.
Applying the biocontrol agent as seed-
ling dip is more economical compared
with fungicide maneb applied as

Identification of Phytophthora Isolates
Pathogenic to Coconut and Closely
Related Species by Isozyme Analysis
Through Starch Gel Electrophoresis.
E.C. Manohar. PCA, Lucena City.

Isoenzyme analysis, commonly
used in genetic studies is recognized
as a useful tool in fungal taxonomy.
This biochemical "fingerprinting" was
used to complement the morphological
characters in determining variations
and in the identification of

Phytophthora isolates pathogenic to
coconut. Isolates from Indonesia, Ivory
Coast and Philippines were subjected
to isoenzyme analysis using four
enzyme systems and three buffer
systems. Based on the electrophoretic
banding patterns, fodr pathogenic
species of Phytophthora associated
with bud rot and nutfall of coconut are
tentatively identified as P. palmivora,
P. arecae, P. parasitica and
P. katsurae. The analysis also showed
a very close affinity of P. palmivora
with P. arecae isolates from the

Reactions of Selected Coconut
Cultivars to Phytophthora Infection in
the Philippines. E.C. Manohar and R.G.
Abad. PCA, Davao City.

The coconut growing regions in
the Philippines cover the three big
islands Luzon, Visayas and Mindanao.
Surveys showed high incidences of the
disease in Mindanao particularly the
Davao provinces where MYD x WAT
hybrids were planted in large coconut
plantations. Local cultivars (Laguna
Tall) affected by bud rot were confined
mainly to the highlands. Indexing of
disease incidence in MULTILOC trials
multilocationn testing of promising
hybrids and cultivars in the Philippines)
showed higher cases of bud rot and
nutfall infections on hybrids with MRD
and MYD parentage. Natural and
artificial inoculations to assess the
reactions of parent materials used in
the PCA hybrid production program is
likewise a major endeavor.

Rice Sheath Blight Spread: A Case
Study On Focal Expansion in Plant
Disease Epidemiology. N.P. Castilla,
F.A. Elazegui and S. Savary. IRRI,
College, Laguna.

The effects of nitrogen supply,
inoculum source structure, leaf
wetness regime and plant-to-plant
contact frequency on the spread of rice
sheath blight caused by Rhizoctonia
solani Kuhn were studied under field
and semi-controlled conditions.

Philipp. Phytopathol. 1994, Vol. 30(2): 122-143

Field experiments were conducted
during the 1992-93 rainy and dry
seasons with three nitrogen input
levels (0, 80 and 120 kg N/ha) as main
plots and five inoculum source
structures as subplots in a split-plot
design with eight replications.
Increasing nitrogen supply to the crop
had strong effect on the rate of focal
spread of the disease. The effect of
inoculum positioning (lower vs. upper
layer of the canopy) on the focus area
lasted longer than the effects of
inoculum amount (5 vs 15 g). Changes
in the leaf wetness and in the contact
frequency between hills are the driving
factors in the spread of sheath blight.
The inoculum efficiency of sheath
blight as influenced by nitrogen
content of the host plant, leaf wetness
regime and contact frequency, was
studied in monocyclic experiments.
The accumulation of wet and dry
periods, decreasing nitrogen content
and higher plant contacts increased the
inoculum efficiency. The apparent
contradiction between the negative
effect of nitrogen content of the host
plant on inoculum efficiency and the
positive effect of nitrogen supply to
the crop on disease spread illustrates
the complex interactions among
individual components of a

Sweet Potato Feathery Mottle Virus:
Its Association with Kamote Kulot,
Distribution and Effect on Yield. L.C.
Villegas, G.L. Pamulaklakin, E.E.
Beduya and N.B. Bajet. UPLB, College,

Enzyme linked immunosorbent
assay (ELISA) and graft transmission
were used to detect sweet potato
feathery mottle virus (SPFMV) in
Ipomoea batatas using both
symptomatic and symptomless
samples collected from the field. ELISA
results showed that SPFMV was
detected in the extracts of about 33%
of the total samples from Albay, 53%
from Tarlac, 67% from Laguna, 71%
from Pampanga, and 82% from

Philipp. Phytopathol. 1994, Vol. 30(2): 122-143

Zambales. Grafting of the symtomatic
ELISA positive samples onto stocks of
I. setosa resulted in the development
of vein clearing on leaves of I. setosa
22 days after grafting.

Comparison of SPFMV-infected
sweet potato cultivars UPL-SP1, UPL-
SP2, UPL-SP5 and Campbell and non-
SPFMV infected plants of the same
cultivars showed that root yield losses
of 98.10%, 97.28%, 95.83%, and
84.55% were incurred by SPFMV on
cultivars UPL-SP5, UPL-SP2, UPL-SP1,
and Campbell, respectively. Fifty
percent reduction in number of storage
root was observed in cultivars UPL-
SP1 and Campbell while UPL-SP2 had
66.67% and 80% reduction for UPL-
SP5. Top weight losses observed on
cultivars UPL-SP1, UPL-SP2, UPL-SP5,
and Campbell were 92.0%, 85.4%,
86.3% and 83.5%, respectively.

Studies on Papaya Virus in the Philip-
pines: I. Etiology, Identification and
Characterization of Papaya Ringspot
Virus in the Philippines. A.C. Talens
and B.S. Alcantara. UPLB, College,

Survey, visual observation and
serological detection by enzyme linked
immunosorbent assay (ELISA)
confirmed the presence of the papaya
ringspot virus (PRSV) disease in most
of the areas in Regions I, IV and V.
PRSV was visually noticeable in
southern parts of the Bicol region and
in isolated islands of Palawan. The
absorbance readings (OD 405nm)
observed from the ELISA indicated that
all the papaya leaf samples tested
reacted positively with the specific
PRSV-antiserurm (As) used.

Denaturing SDS-polyacrylamide
gel electrophoresis (SDS PAGE),
Western blotting and immunosorbent
electron microscopy were also
performed to further characterize the

virus and also to determine the
presence of any viral strains. Results
revealed the presence of a major
protein with a molecular weight of
about 36 kd in all the samples tested.
Other minor protein bands with mw of
about' 31 and 26 kd were also
observed in some samples indicating
variations among the isolates. All
isolates except one showed flexuous
virus particles decorated with the
homologous PRSV antiserum. The pre-
sence of decorated and nondecorated
virus particles in one isolate indicates
the possibility of double infection.
Further tests are being done to verify
the results.

"An-An": A Disease Infecting Passion
Fruit in Quezon Province. P.M. Barcial,
N.B. Bajet and F.C. Quebral. UPLB,
College, Laguna.

A previously unreported and
undescribed disease infecting passion
fruit (Passiflora edulis) referred to as
"An-An" was found in Lucban,
Quezon. Symptoms on affected vines
are mottling of leaves and vine
terminals/shoots. Leaves become
distorted and malformed as the disease
progressed. Fruits are wrinkled,
deformed and discolored. These are
symptoms characteristics of virus
infection. Electron microscopy,
symptomatology and host range
studies were conducted to determine
the nature of the disease.

Leaf dip preparations of "an-an"
infected leaves contained flexuous rod
virus-like particles which were not
observed in healthy leaves. No such
virus like particles were observed in
healthy asymptomatic leaves. The virus
was mechanically transmissible to
Passiflora edulis, P. foetida,
Chenopodium amaranticolor, C.
quinoa, Cassia occidentalis and
Phaseolus lathyroides but not to

Nicotiana tabacum and N. glutinosa.
Local lesions developed on
C. amaranticolor and systemic symp-
toms on P. edulis, P. foetida, C.
occidentalis, P. lathyroides and C.
quinoa. Further studies are being
conducted to classify this putative
virus associated with "an-an".

Bacterial Stem Blight of
Chrysanthemums in the Philippines.
R.G. Bayot, G.G. Divinagracia, O.N.
Bayot and F.C. Jovero. UPLB, College,

A disease of chrysanthemum
resembling bacterial stem blight was
observed in cut flowers from Baguio
(white flower variety) and from Cebu
(yellow flower variety) during the
months of June and July. Initial
symptoms appear as water-soaked
lesions. Lesions become gray to black
in color as they enlarge and may
coalesce and cause extensive damage
of stems. The disease also causes
rotting of the young stems, axilliary
buds and flowers.

Bacterial cells were found
associated with the lesions. Whitish to
creamy colonies developed on potato
dextrose peptone agar after 24 hours.
The isolate did not produce fluorescent
pigment on King's B medium. Bacterial
cells were Gram-negative, rod-shaped,
facultative anaerobe, caused rot in
potato, liquefied gelatin, produced H2S
from peptone and produced acid from
lactose and mannitol but not from

Pathogenicity test was done by
wounding the stem of chrysanthemum
with a scalpel and placing the bacterial
suspension onto the wound using a
dropper. Water-soaked lesions
appeared on inoculated stems after 4
days. The lesions enlarged and turned
black with time. The bacterium causing

Philipp. Phytopathol. 1994, Vol. 30(2): 122-143

stem blight of chrysanthemum in the
Philippines is probably Erwinia
chrysanthemi. Further physiological/
biochemical tests will be done to
confirm the diagnosis.

Occurrence of Fusarium Wilt Disease
of Abaca in Leyte. L.M. Borines and
A.A. Baliad. ViSCA, Baybay, Leyte.

Different abaca growing areas in
Leyte, namely, VISCA, Mahaplag,
Danao, Maglahug, Sta. Fe, Abuyog, La
Paz, Sogod, Bontoc and Maasin were
surveyed for the occurrence of
fusarium wilt disease caused by
Fusarium oxysporum f.sp. cubense.
Among these areas, the disease was
observed only in Mahaplag, La Paz,
Danao and Maglahug with disease
incidence of 64, 55, 26, and 4%,
respectively. The disease was generally
severe in areas with higher elevation,
with always humid and wet soil
conditions. Fusarium wilt is sometimes
found in association with bacterial wilt
in La Paz and abaca mosaic in Danao.

Mechanical Transmission of the
Coconut Cadang-Cadang Viroid
(CCCVd) Using Harvesting Tools. G.G.
Manalo and Ma. J.B. Rodriguez. PCA,

We investigated the field
transmissibility of the coconut cadang-
cadang viroid (CCCVd) through
mechanical means. Three-month old,
screenhouse-grown Laguna coconut
seedlings were subjected to different
frond slashing treatments at 45-day
intervals. The blade used was either
dipped in CCCVd inoculum or cut into
CCCVd-infected coconut fronds.
Biannual monitoring for CCCVd
infection was done on leaf sample
extracts by polyacrylamide gel
electrophoresis (PAGE) assay.

Philipp. Phytopathol. 1994, Vol. 30(2):122-143

After three and a half years from
the first frond slashing treatment,
palms subjected to 10 times slashing
with the blade previously dipped in
CCCVd inoculum were positive with
the viioid by PAGE assay. Mechanical
transmissibility of the CCCVd in the
field using a farm implement has been

Population Dynamics of Plant Parasitic
Nematodes As Affected By Volcanic
Ash. J.D. Recuenco. SRA, Pampanga.

Analyses of soil samples from
sugarcane fields in two mill districts,
Pasumil and Pasudeco with 0 to 24 cm
depth of volcanic ash, showed
variation in nematode population
densities as the depth of volcanic ash
changed. Fields covered with 12 to 24
cm volcanic ash had lower nematode
population densities than those
covered with 1 to 9 cm. Fewer
nematodes were observed on the plant
canes than on the ratoon canes at
different depths of volcanic ash.

Nine genera of plant parasitic
nematodes (Pratylenchus, Tylenchor-
hynchus, Rotylenchus, Criconemella,
Helicotylenchus, Xiphinema, Hoplolai-
mus, Hemicycliophora and Praty-
lenchus) were found associated with
sugarcane at different depths of volca-
nic ash. Pratylenchus and Tylenchor-
hynchus predominated over the other
genera of plant parasitic nematodes.
Their population densities were low
during germination or tillering stage (1-
4 months) of sugarcane, peaked at
vegetative and stalk elongation stage
(5-8 months) and declined at
ripening/maturity stage (9-12 months).

The amount of volcanic ash in the
soil exerts significant reduction of
nematode population densities in the
sugarcane fields. Information on the
population changes and the prevalence

of parasitic nematodes in these
volcanic ash-laden sugarcane fields
gives essential knowledge in evolving
component technologies for integrated
nematode management on sugarcane.

Weed Hosts Of Pratylenchus zeae and
Meloidogyne graminicola and Reactions
Of Upland Rice To The Nematodes.
R.M. Gapasin and E.B. Barsalote.
ViSCA, Baybay, Leyte.

Upland weeds such as Ageratum
conyzoides, Eleusine indica, Paspalum
dilatatum, Vernonia cinerea and
Digitaria ciliaris were potential alternate
hosts of Pratylenchus zeae. Among the
66 upland weed species artificially
inoculated with Meloidogyne
graminicola, 10 (15.15%) were found
hosts as indicated by the presence of
galls and eggs in their root systems.

Reduction in the height, top and
root weights of upland rice (cv.
Lubang) inoculated with P. zeae were
evident at inoculum densities of 3,000
and 5,000.

Of the 52 upland rice cultivars and
lines evaluated for their reactions
against M. graminicola, IR 62761-20,
IRAT 610 and IR 60080-48 were
found resistant to the nematode. The
rest were either moderately resistant or

Incidence and Severity Of Brown Spot
(Helminthosporium oryzae) and Other
Major Diseases Of Rice In Zamboanga
City. J.P. Pedroso, R.D. Yumol and
A.A. Ducanes. WMSU, Zamboanga

A survey was conducted to
determine the incidence and severity of
brown spot disease caused by
Helminthosporium oryzae in the
Western and Eastern Coasts of

Zamboanga. Seven barangays were
surveyed from September 1992 (wet
season) to May 1993 (dry season).
Fields were divided into zones, and
paddies within a zone were
randomized. Thirty percent of the
paddies were taken as samples.
Disease severities were assessed using
a descriptive rating scale.

Results revealed that brown spot
occurred in all rice fields in Zamboanga
City. Severity of infection ranges from
25 to 75 percent. Western Coast areas
were severely infected during dry
season since varieties used by farmers
were susceptible to brown spot at all
stages of growth. Other diseases of
major importance were Cercospora
leafspot (Cercospora oryzae),
Rhizoctonia leaf blight (Rhizoctonia
solani), false smut (Ustilaginoidea
virens), "yellow spot" (unknown agent)
and rice tungro.

Quantification of Brown Spot Effects
on Rice Yield Using Microplots in
Farmers' Fields. J. Pedroso, R. Yumol,
A. Ducanes, P. Lacbao and T. Narvas.
WMSU, Zamboanga City.

Three 4m2-microplots in each of
the twelve farmers' fields in Barangay
Cawit, Zamboanga City, were
established during the dry season
1993 (March-June). Ten tillers per
microplot were assessed at five growth
stages (GS) eg. GS 20, 40, 60, 100
days after planting (DAP) for
percentage severity of brown spot (BS)
and other biotic factors. At harvest,
elemental analysis was conducted for
NPK on stems and leaves, and bulk
yield and yield com onents were
determined from 20.5m samples per
microplot. On IR74 and "Bordagul", BS
severities (mean of 10 tillers) ranged
from 7-39% at GS 20, 16-40% at GS
40, 16-45% at GS 60 and 22-68% at
GS 100. All growth stages were

Philipp. Phytopathol. 1994, Vol. 30(2): 122-143

assessed using a decimal code. At
harvest, leaf N ranged from 0.6-1.2%,
leaf P from 0.02-0.06%, leaf K from
0.9-2.0% while stem NPK were,
respectively, 0.4-0.7%, 0.03-0.08%
and 1.9-3.1%. BS severity at GS 40,
GS 60 and GS 90 were significantly
correlated with bulk yield, with r-values
of -0.71 (**), -0.55(*) and -0.72(**),
respectively. Leaf N was positively
correlated (r=0.57**) while leaf P was
negatively correlated (r=0.58**) with
BS severity at GS 90. Leaf K was not
correlated with BS severity at any GS.
Stem N and P were correlated with BS
at GS 40 (r=0.59**, r=0.72**,
respectively) and at GS90 (r=0.53**,
r=0.59**, respectively). Stem K was
not correlated with BS. Our results
showed that increasing N tend to
increase BS severity, increasing P
decreased BS while K had no effect on

Survey on the Effect of Volcanic Ash
Fall on the Occurrences of Sugarcane
Diseases in Pasumil and Pasudeco Mill
Districts. R.C. Sampang, A.M. Burcer
and A.N. Manlapaz. SRA, Pampanga.

Volcanic ash fall had affected the
occurrences of sugarcane diseases in
Pasumil and Pasudeco mill districts.

Higher percent infection due to
smut and downy mildew, red rot of the
midrib and leaf sheath was observed
on fields with more ash fall. Minimal
infection due to banded sclerotial
disease and pokkah-boeng was
observed on all depths of ash fall while
higher ring spot infection was noted on
fields with lesser ash fall on 6-12
month old plants and ratoon canes.

Comparisons on the results of
disease surveys on the districts before
and after the volcanic eruption showed
that volcanic ash fall resulted to low
infection due to mosaic and red rot of

Philipp. Phytopathol. 1994, Vol. 30(2): 122-143

the leaf sheath but high percent
infection due to smut, downy mildew
and red rot of the midrib was

Probing the Ability
solani Isolates from
Species to Infect
Raymundo, M.R.
Pamplona and P.S.
College, Laguna and

of Rhizoctonia
Different Host
Rice. A.D.
Pantua, R.S.
Teng. UPLB,
IRRI, College,

Isolates of Rhizoctonia solani from
different host species namely, corn,
sorghum, wheat, cabbage, potato,
sugarcane, Rottboellia exaltata, and
Cyperus rotundus, that are planted in
rotation with rice or weed species in
ricefields, were tested on rice cultivar,
IR72 in two trials to determine cross-
infectability. On the basis of actual
lesion length (ALL), relative lesion
length (RLL), percent severity per hill
(PSH), and area-under-the-disease-
progrerss curve, significant differences
among isolates were observed. In both
trials, the isolate from cabbage (RSC)
showed a very low degree of virulence
on rice. No symptom of sheath blight
was elicited by the potato isolate
(POT). Although significant differences
were observed among the other
isolates in terms of all the parameters
measured, the magnitude of disease
was considerable in all cases. For
instance, during the second trial,
isolates POT and RSC caused actual
lesion length of zero and 12.3 cm
respectively, while the rest of the
isolates produced ALL in the range of
71.5 to 97.4 cm.

The level of disease during the
second trial was substantially higher
than that observed-during the first trial.

Consequently, the rates of infection

Sheath Blight, a Threat to Intensive
Rice Production Systems. R. Cu, T. W.
Mew, K. G. Casman, and P. S. Teng.
IRRI, College, Laguna.

Sheath blight of rice, caused by
Rhizoctonia solani has been demons-
trated as serious problem in intensive
rice production systems. Three rice
cultivars (IR72, IR59682-132-1-1-2
and IR60819-50-3-3) were grown in
intensive system with high levels of
chemical inputs and four rates of nitro-
gen fertilizer. Grain yield, components
of yield, tissue analysis for NPK, and
soil nutrient analysis as well as disease
incidence were assessed. Incidence of
blast, foot rot and narrow brown spot
were low due to adequate fungicide
treatment. Sheath blight incidence,
however, was high inspite of the
fungicide treatment. The 1993 dry
season experiment showed about 30%
sheath blight incidence. In 1992 dry
season, a grain weight reduction of
32% resulted from sheath blight
infection at the higher nitrogen level.
The 10.4% of tissue infected with
sheath blight can be translated to a
yield loss of about 295 kg/ha. The
disease was found to be a significant
yield-limiting factor. It is assumed that
nitrogen plays an important role in the
dynamics of the disease because
higher incidence of sheath blight was
particularly found in treatment plots
with high nitrogen input. Higher di-
sease incidence could counteract the
incremental increase of yield due to
higher nitrogen rates. Novel
approaches to sheath blight control
that can effectively manage the
disease will allow farmers to apply
higher rates of nitrogen to achieve
higher yield targets.

Yield Effects of Nitrogen-Water-Crop
Injury Interactions in Rice. H.O.
Pinnschmidt and Ma. A.M. Galon. IRRI,
College, Laguna.

Field trials were conducted in the
dry and wet seasons of 1993 at IRRI
to study effects of nitrogen-water-crop
injury interactions on yield
components. The crop was subjected
to various irrigation schemes in
combination with zero and high
nitrogen fertilizer applications. Artificial
crop injury treatments (which were
achieved by spraying of muriatic acid
and clipping of tillers to simulate leaf
spotting and detillering organisms,
respectively) were super-imposed to
this set-up in P strip-split-plot design.

Nitrogen level and crop injury
treatments have significant yield
effects. No significant interactions
among treatment factors were
observed. Early crop injury did not
significantly reduce yield, while late
crop injury did. With increasing levels
of yield loss due to single injury types,
yield-reducing effects to combine injury
types shifted from greater-than
additive to less-than-additive,
compared to summing-up the effects
of single injury types.

Determining the Importance of Insects
and Wounding to Aspergillus Kernel
Infection and Aflatoxin Contamination
of Corn. R.P. Garcia and H.A. Barrios.
NCPC-UPLB, College, Laguna.

Field experiments were conducted
at the Department of Agriculture-
Cagayan Valley Integrated Agricultural
Research Center (DA-CVIARC), Ilagan,
Isabela during the dry and wet seasons
of 1993 to determine the importance
of insects and ear damage to
Aspergillus kernel infection and
aflatoxin contamination. The
experimental design was RCBD with 8

Philipp. Phytopathol. 1994, Vol. 30(2): 122-143

treatments and 5 replications.
Inoculation was done at 20-day old
seedlings and wounding was simulated
at 50% silking stage of corn. At
harvest, kernels adjacent and away
from the wounded areas were plated
on Malt Salt Agar (MSA) and aflatoxin
was extracted and quantified by thin
layer chromatography.

In the dry season crop, there was
an apparent correlation between
wounding and insecticide application
and the extent of kernel damage/ear,
kernel infection and aflatoxin content.
The wounded, inoculated and no
insecticide applied gave the highest
value for the abovementioned
parameters compared with all
treatments in kernels adjacent and
away from the wounds. Similar trend
was observed in the wet season crop
except for some unwounded
treatments giving higher kernel
infection compared to wounded ones.
This could be attributed to insects'
attack which created wounds or
injuries for the entrance and infection
of other fungal species.

Wounding and insecticide
application play an important role. in
preharvest kernel infection by A. flavus
and the subsequent aflatoxin
contaminations. However, the specific
effect of each could not be well
delineated because of the interaction
with varying environmental conditions
prevailing in the field.

Pollution (Abiotic) Damage
Agricultural Vegetation in
Philippines. F.C. Quebral,
Navasero, V.R. Daquioag and
Barcial. UPLB, College, Laguna.


The Plant Pest Clinic of UPLB has
recorded during the last five years the
various crop maladies induced by
pollutants or abiotic factors. In Region

Philipp. Phytopathol. 1994, Vol. 30(2): 122-143

IV alone, an estimated 20-million pesos
worth of damage occurs annually on
the following crops: rice, guapple
trees, citrus, lanzones, gabi, tomato,
garlic, coconut, corn, etc.

Crop injuries were manifested in
the form of growth suppression or
stunting, chlorosis or other color
changes, collapse of leaf tissues, early
leaf drop, delayed maturity, abortion of
blossoms and reduced yield. The
extent of damage is governed by the
kind and concentration of pollutant,
time of exposure, plant age, plant
species or varieties, land contours and
meteorological factors (wind direction,
moisture, temperature, humidity).

The pollutants that caused crop
damage were cement, brine, sulfur,
ammonia, pesticides, fertilizers and
other factory wastes. Specific case
studies are cited

Intraracial Variation in Virulence and
Host Adaptation of Xanthomonas
oryzae pv. oryzae on Rice. C.C. Mundt,
M.R. Finckh and R.F. Alfonso. IRRI,
College, Laguna.

Two near-isogenic rice (Oryza
sativa) lines possessing either the Xa4
or Xa10 resistance gene against
Xanthomonas oryzae pv. oryzae,
causal agent of bacterial blight of rice,
were grown in two irrigated lowland
fields in Calauan and Mabitac, Laguna
during the 1993 wet season. High
incidence of bacterial blight are known
to be endemic in these locations.
Symptomatic leaves were collected late
in the season and bacteria were
isolated from a maximum of 20 leaves
per plot, resulting to approximately
160 and 140 isolates from Mabitac
and Calauan, respectively. Bacteria
were tested on two replicate sets of

three differential hosts: the two near-
isogenic lines and the susceptible
recurrent parent IR24. Bacterial
populations were predominantly race
3, which were compatible with both
original hosts. However, populations
had increased virulence on the host of
origin (as measured by lesion length) in
three of four cases. We conclude that,
despite the clonal nature of X. oryzae
pv. oryzae, there is much selectable
variation for virulence present even
within a single race of the pathogen.

Screening of Rice Varieties and
Selections for Resistance to Brown
Spot (Helminthasporium oryzae) in
Zamboanga City (Wet Season, 1992).
A.A. Ducanes, J.P. Pedroso and R.D.
Yumol. WMSU, Zamboanga City.

One hundred fifty and 30 irrigated
lowland and rainfed cultivar entries,
respectively, were screened for
resistance to brown spot of rice from
July to November 1992 in farmers'
field in Tulungatung, Zamboanga City.
Entries were grouped according to
maturity and disease assessment was
done at different growth stages.
Results showed that lowland varieties
including Bordagol, a farmers' variety
were moderately susceptible and
susceptible at seedling and booting
stages, respectively. Disease severity
increases as crop matures. No
significant difference exist among
entries at different growth stages,
except at ripening stage where disease
severity increased significantly. Yield
was slightly affected by brown spot of

BPIRi 10 and PSBRC4 varieties
showed moderate resistance to brown
spot. Other varieties were susceptible
to infection. Lowland rainfed varieties
were highly susceptible to the disease.

Symptomatic Resistance to Rice Tung-
ro Bacilliform Virus. R.C. Cabunagan,
Z.M. Flores and H. Koganezawa. IRRI,
College, Laguna.

Many varieties available in the IRRI
rice germplasm collection show
resistance to rice tungro spherical virus
(RTSV) while only a few are resistant
to rice tungro bacilliform virus (RTBV).
However, some varieties had low
symptom severity score, an indication
of symptomatic resistance. Based on
the results of the mass screening tests,
we selected 67 varieties and further
evaluated their reaction to tungro
infection. Thirty 6-day old seedlings
per variety were separately confined
for 24 hr in a test tube with three
newly emerged green leafhopper (GLH)
adults fed on plants infected with
RTBV and RTSV. Ten seedlings were
kept uninoculated to serve as control.
The seedlings were transplanted at the
rate of five seedlings per pot and
grown in a greenhouse for one month.
Plant height was then measured and
symptom severity scored and indexed
by ELISA. Two trials were conducted.
Except for ARC11554, all the varieties
showed consistently low symptom
severity scores. These varieties also
showed very low reduction in height
despite of the infection. Utri Merah,
Balimau Putih and Utri Rajapan con-
sistently showed relatively low RTBV
concentrations. These results indicate
that many varieties in the rice germ-
plasm collection are a source of symp-
tomatic resistance to RTBV and could
be used as sources of resistance in rice
breeding programs.

Philipp. Phytopathol. 1994, Vol. 30(2): 122-143

Occurrence, Alternate Hosts of and
Resistance to Phakopsora pachyrhizi.
F.M. dela Cueva, M.P. Natural and M.
Kakishima. IPB, UPLB, College, Laguna
and Univ. of Tsukuba, Japan.

Soybean growing areas in Luzon
and Mindanao were surveyed for the
occurrence of soybean rust caused by
Phakopsora pachyrhizi. Soybean rust
was found in Davao, Cotobato,
Bukidnon, Isabela, Cagayan, Albay and
Los Baios, Laguna.

Of the 23 weed species inoculated
with spores of P. pachyrhizi, four
species showed positive reactions.
These were Calapogonium sp, Centro-
sema sp., Crotalaria sp., and Desmo-
dium sp. Uredosori started to appear 7
days after inoculation and examination
under a light microscope showed
numerous uredospores in one sorus.

The resistant genotypes, UPLSy6,
IPB Sy 83 52-10 and UPL Sy4
exhibited significantly longer latent
period than the susceptible cultivar, TK
5. Relative to TK 5, there were 33 and
22% delay in latent period in resistant
and moderately resistant genotypes,

UPLSy 6, a rust resistant soybean
variety, had the smallest stomatal
length (0.63 u) and width (0.11 u) and
the highest trichome number (ave. of
82.11) while TK 5 had an average
trichome number of 55. Resistance of
UPLSy 6 to soybean rust seemed
attributed to small stomatal aperture
and a high number of trichomes.

Philipp. Phytopathol. 1994, Vol. 30(2): 122-143
Screening of Rice Varieties and
Selections for Resistance to Brown
Spot Caused by Helminthosporium
oryzae (Dry Season, 1993). R.D.
Yumol, J.P. Pedroso and A.A.
Ducanes. WMSU, Zamboanga Ciiy.

Each entry was transplanted in
three row 0.6m by 5.0m area.
Randomized Complete Block Design
(RCBD) was used with
varieties/selections as treatments
replicated three times.

Ninety seven rice varieties and
selections were screened for resistance
against brown spot in the farmers field
at Barangay Ayala, Zamboanga City.
No infection was observed at 30 days
after planting (DAP). However,
Bordangol, a farmers variety and three
early maturing selections, namely
PR23457-11, PR23372-28, PR23489-
4 were infected at 45 DAP and rated
susceptible. All other rice varieties and
selections were rated moderately sus-
ceptible or susceptible to the disease
at booting and harvesting stages. The
yield of the sixteen varieties and
selections were significantly higher
compared with Bordagol.

Effect of Roguing on Incidence of Rice
Tungro Disease. E.R. Tiongco, T.
Chancellor, J.M. Thresh, M.M.
Magbanua and P.S. Teng. IRRI,
College, Laguna.

The effects of removing plants
infected with tungro on IR22,
susceptible to green leafhopper and
tungro disease, and IR36, moderately
resistant to green leafhopper and
tungro disease, at weekly intervals
starting at 14 days after transplanting
(DAT) until 6-7 weeks later to control
the spread of the disease were studied
in the 1992 wet season and dry
season and 1993 wet season
croppings. Another roguing treatment

was added in the 1993 trial. Roguing
was done at 21 and 28 DAT. No
significant differences in tungro
disease incidence, green leafhopper
vector count, and grain yield were
obtained between rogued and non-
rogued plots of IR22 and IR36 in the 3
trials. The results indicate that
conducting roguing operations at 21
and 28 DAT and even at weekly
intervals to control the spread of rice
tungro disease in the field was

Biological Control of Rice Sheath Blight
Under Field Conditions. G.V. Maningas
and T.W. Mew. IRRI, College, Laguna.

We evaluated some potential
biological control agents that were in
vitro and in greenhouse previously
tested under field condition for three
seasons, 1992 and 1993 wet season
and 1993 dry season in IRRI
experimental farm. Pseudomonas
cepacia and Pseudomonas putida, in
singly and in mixture, were tested as
seed bacterization and as spray on
transplanted and direct seeded IR72.
Sterile water and fungicide
(Validamycin) were used as controls.
Plots arranged in randomized complete
block design were inoculated with
Rhizoctonia solani on sterile rice grain-
rice hull substrate (1:3) at maximum
tillering. Sheath blight incidence and
severity (relative lesion height) were
assessed on 20 randomly selected hills
at three growth stages; 7 days after
inoculation, at flowering and at
harvest. Results showed that the effect
of biological control agents, either used
singly or in mixture, produced erratic
effect over time on sheath blight
severity although there was a
significant reduction on sheath blight
severity on treated plots, such
reduction was unpredictable and vary
with seasons. Infectivity of .sclerotia
collected from biological control agents

and fungicide treated plots was
significantly reduced as compared with
control treatment. Number of effective
tillers and plant height were not
significantly different among
treatments. However, higher yields
were observed on plots treated with
biological control agents over the

Evaluation of Plant Extracts as
Fungicidal Material Against Major
Fungal Diseases of Root Crops. C.E.
Sajize-del Rosario and A.P. Molato.
ViSCA, Baybay, Leyte.

In vitro bioassay was conducted
to evaluate extracts of local plants for
their fungicidal activity against major
fungal pathogens of root crops. Out of
the 12 plant species screened, nine
exhibited fungicidal activity to one or
more root crop fungal pathogens.
Ampalaya leaf extract was found
effective against Botryodiplodia
theobromae, Sclerotium rolfsii,
Phytophthora colocasia, Curvularia
luneta and Colletotrichum
gloeosporioides; saluyot was inhibitory
to the growth of P. colocasia and
B. theobromae; kulitis was effective
against P. colocasia; kamantigue
inhibited the growth of S. rolfsii,
C. lunata, B. theobromae, Sphaceloma
batatas and C. gloeosporioides; ginger
was found effective against C. lunata,
Fusarium solani and S. rolfsii, olasiman
inhibited C. gloesporioides; mikania
and ipil-ipil inhibited S. batatas.

Pot experiment indicated that
crude extracts of ampalaya, saluyot,
kulitis, kamantigue and olasiman were
more effective as protectant than as
therapeutant against C. gloesporioides
and P. colocasia.

Philipp. Phytopathol. 1994, Vol. 30(2):122-143

Effect of Solarization on Bacterial Wilt
Incidence R.G. Bayot and E.A. Acosta.
NCPC, UPLB, College, Laguna.

The effect of solarization on
bacterial wilt incidence was determined
by tarping or covering Pseudomonas
solanacearum infested plots with
plastic sheets for 4 and 6 weeks
during the summer months.
Temperature readings in plastic-
covered and uncovered plots were
recorded daily. Susceptible tomato
plants (cv. Yellow Plum) were used as
test plants and bacterial wilt incidence
was monitored for 2 months.

Mean incidence of bacterial wilt in
plots covered with plastic sheets for 4
weeks was 35.9% compared with
58.0% in uncovered plots (38.0% wilt
reduction in plastic-covered plots).
After 6 weeks of solarization, plastic-
covered plots had 21.4% wilt
incidence while uncovered plots had
51.8% of wilt incidence (58.6% wilt
reduction in plastic-covered plots). The
temperature in plastic-covered plots at
1:30-2:00 p.m. ranged from 40-65 C
with a mean of 51.2 C while the
temperature in uncovered plots ranged
from 30-39 C with a mean of 34.6 C
from March 17 to April 27, 1993.

Control of Aspergillus ochraceus and
Penicillium viridicatum on Corn and
Copra Using Ammonia. R.P. Garcia and
M.V. Pantua. NCPC-UPLB, College,

The efficacy of the different
forms, concentrations and methods of
application of ammonia against
Aspergillus ochraceus and Penicillium
viridicatum were tested in vitro by

Philipp. Phytopathol. 1994, Vol. 30(2):122-143

inoculating the two fungi on agar and
broth media infused with 0.05, 0.1,
0.5, 1.0 and 2.0 percent ammonium
hydroxide (NH40H) and ammonium
sulfate [(NH4)2 SO4] to determine its
effect on mycelial growth, sporulation,
spore germination and ochratoxin
production. In vivo test was conducted
by monitoring infection, seed
germinability and ochratoxin
production for six months to evaluate
the protective and therapeutic effects
on corn and copra. Result showed that
NH40H was more effective in
inhibiting colony diameter and
sporulation than (NH4)2SO4, hence,
NH40H was selected for further tests.
No mycelial growth was observed on
agar medium with 2.0% NH40H and
on broth culture with 1.0 and 2.0%
NH40H after 7-10 days. Sporulation
was similarly abundant at 0.05, 0.1
and 0.5% NH40H. Spore germination
was completely inhibited at 1.0 and
2.0% NH40H after 24-36 hours.
Ochratoxin was not detected in
Czapek's broth treated with 2.0%
NH40H and very minimal toxin was
detected in the broth with 1.0 and
0.5% NH40H. Small scale storage of
corn and copra revealed that the
treated samples have low incidence of
P. viridicatum infection compared with
the control. Corn seeds treated with
2.0% NH40H had higher germination
compared with the other treatments.
The results clearly indicate that A.
ochraceus and P. viridicatum on corn
and copra may be controlled effectively
by NH40H treatment.

Biological Control of Eleusine indica (L.)
Gaertn. With a Fungal Pathogen. C.B.
Yandoc and A.K. Watson. IRRI,
College, Laguna

An indigenous fungal isolate was
used under controlled environmental
conditions and was found to
effectively control Eleusine indica

plants. Mortality of young E. indica
seedlings was 98% 14 days after
inoculation. Mortality was reduced
when older plants were inoculated, but
plant biomass was significantly
reduced even when inoculated plants
were as old as 7 weeks. The fungus
caused flecking and dark brown
narrow elongated and spindle-shaped
lesions on leaves 24 hr after
inoculation with 104 spores/ml and
incubation in the dew chamber for 24
hr at 25 C. Blighting of leaves occurred
thereafter. Experiments with shorter
dew periods indicate that a minimum
of 8 hr dew period is favorable for
disease development and significant
reduction in biomass of E. indica plants
while with older plants, a minimum of
16 hr dew period is necessary for
effective control.

Studies of Papaya Viruses in the
Philippines: II. Control Management of
Papaya Ringspot Virus in the
Philippines. A.C.D. Talens and B.S.
Alcantara. NCPC, UPLB, College,

Search for other alternative hosts
for the papaya ringspot virus (PRSV)
was conducted using ELISA. Results
showed that* two out of 12 weed
species collected from areas where
papaya trees are grown tested
positively against the specific PRSV
antiserum. The weed species were
Diplocyclos pa/matus and Centrosema
pubescens. Other plant spp. as
potential natural hosts were Luffa
acutangula and Cucurbita pepo. The
association of PRSV particularly to the
weed spp. are being confirmed by
electron microscopy (EM) and
biological assay using C. pepo or
Carica papaya as indicator host plants.

The importance of intercropping
as a control strategy for PRSV is also
being investigated. Four different sites

are being evaluated for this purpose.
Results- have indicated that
intercropping combined with other
cultural management such as roguing
and sanitation or removal of weeds
and other natural hosts of PRSV can
delay the onset and spread of the
disease in the field.

Soft Rot of Unripe Bananas. M.P.
Natural, M.G.B. Razote and R.M. dela

A rod-shaped, Gram negative, fa-
cultatively anaerobic bacterium caused
soft rot of unripe bananas. Various
tests identified the causal bacterium as
Erwinia carotovora subsp. carotovora
that was specific in bananas. Carrot
and cabbage isolates of E. carotovora
subsp. carotovora failed to cause soft
rot in green, unripe bananas.

Temperature had a pronounced
effect on the rate of disease develop-
ment. Fruits incubated at 30-35C
showed severe rotting 7 days after ino-
culation while fruits incubated at 25C
showed only minimal rotting. Banana
cultivars 'Turdan' and 'Bungulan'
were more susceptible than 'Saba'.

Entry of the bacterium could be
through wounds. Rotting was ob-
served only when inoculation was
done by peel-pricking or by injecting
bacteria to the pulp. No disease was
observed where fruits were sprayed
with a 10 CFU/ml bacterial

Anthracnose of Anthurium andreanum
Andre. M.P. Natural, F. Balmaceda and
Ma. J.C.M. Estrada. UPLB, College,

The causal fungus of anthracnose
or spadix rot of anthurium was isolated
and studied. Based on morphological

Philipp. Phytopathol. 1994, Vol. 30(2):122-143

and cultural studies, and the
characteristic symptoms produced on
anthuriums, the fungus was identified
as Colletotrichum gloeosporioides.
Symptoms varied from small dots to
blackening of the tip of the spadix,
thus termed black nose in other

The fungus showed varied growth
characteristics and conidial production
in various media, Widest mycelial
colony diameter and maximum conidial
production was obtained when C.
gloeosporioides was grown on PDA
adjusted to pH 5.5 and incubated at
room temperature. Corn meal agar,
carrot decoctions agar and tomato fruit
decoction agar also supported the
growth of C. gloeosporioides but the
number of conidia produced was much

Cross-infection of Rhizoctonia solani
Isolate from Azolla to Rice. Ma. J.C.M.
Estrada, R.M. Mendoza-dela Cruz and
M.P. Natural. UPLB, College, Laguna.

Pathogenicity test of Azolla
isolates of Rhizoctonia solani was
conducted on rice seedlings to verify
earlier reports that these isolates were
avirulent to rice. Inoculation revealed
sheath blight symptoms and R. solani
was isolated from infected rice
seedlings. The morphological and
cultural characteristics of isolated
fungus resembled with the Azolla
isolates. Back-inoculation to Azolla
resulted in fronds turning brown and
rotten. Further tests revealed however,
that the R. solani Azolla isolates could
only cause moderate infection to about
70 rice entries included in the NCT dry
season trial.

A rice isolate of R. solani causing
sheath blight was used to cross-infect
azolla. This was found to be virulent
on Azolla microphylla. More than 40

Philipp. Phytopathol. 1994, Vol. 30(2):122-143

Azolla hybrids/lines showed various
reactions to this rice isolate.

Occurrence of Rice Dwarf Disease in
the P-ilippines. P.Q. Cabauatan, R.C.
Cabunagan, Filomena C. Sta. Cruz and
H. Koganezawa. IRRI, College, Laguna.

Symptoms of rice dwarf disease
were observed in rice in Midsayap,
North Cotabato. Infected plants were
stunted and exhibited fine chlorotic
streaks or specks on the leaf blades.
Electron microscopic observation of
clarified sap from infected plants
revealed the presence of rice dwarf
virus (RDV) particles about 65 nm in
diameter. Leaf extracts from
symptomatic leaves gave strong
positive reaction to RDV antiserum in
rapid immunofilter paper assay (RIPA)
and double antibody sandwich enzyme-
linked immunosorbent assay (DAS-
ELISA). Positive transmission of RDV
was obtained with Nephotettix
nigropictus but not with N. virescens
and Recilia( dorsalis. The virus was
persistent in the vector with an
incubation period of about 15 days.
RDV was also transmitted via the eggs
of viruliferous females of N.

Bugtok Disease of Cooking Bananas: I.
Etiology and Diagnostic Symptoms.
C.E. Soguilon, L.V. Magnaye and M.P.
Natural. DNCRDC, Bago Oshiro, Davao
City and UPLB, College, Laguna.

Bugtok disease of cooking
bananas was conclusively found to be
caused by Pseudomonas solanacearum
E.F. Smith. Results of cultural,
morphological, biochemical and
pathogenicity tests revealed striking
similarities between the bugtok
bacterial isolates and P. solanacearum
from other hosts. Bacterial cells were
Gram negative, rod-shaped and

measured about 0.5 to 1 um by 1.5 to
4 um. Colonies on TZCA were
irregular, convex and fluidal with or
without pink centers. Artificially
inoculated tomato seedlings and
banana plantlets wilted. Bugtok
symptoms on fruits were reproduced in
artificially inoculated inflorescence.

Two distinct symptom types were
observed from field infected fruits;
namely, the reddish brown and the
black discoloration of the fruit pulp. In
either case, the fruit pulp was hard
especially in areas that were
discolored. Discoloration was intense
in the core of the fruit. Vascular
tissues in the pedicels, fruits and
stems, and leaf sheaths were also
discolored becoming less intense in
parts that are far from the fruits.

If the male inflorescence (heart)
was detached from the bunch, a
bugtok infected plants can not be
differentiated from a healthy plant.
With the male bud still attached,
bugtok infected plants can be
recognized because the bracts fail to
dehisce, giving it a loose and dry
appearance. Healthy male inflorescence
appear compact and succulent as the
older bracts dehisce successively at

"Red Stripe": A New Rice Disease in
the Philippines. J.F. Barroga and T.W.
Mew. IRRI, College, Laguna.

A new rice disease has been
observed in various rice fields in the
Philippines. It occurred in IR72 (IRRI
farm), in IRBB7 (Calauan, Laguna), in
IR74 and PSBc4 (Zamboanga), and in
Bordagul cultivar (Davao del Sur and
Davao del Norte, North Cotabato,
Zamboanga). The disease was
commonly observed in areas of intense
rice cultivation, with high nitrogen
fertilization. The infection started as

pin-point yellow specks on the leaves.
The lesions were circular to oval in
shape, darkened and turned yellow-
orange, sometimes with the center of
the lesion becoming more distinct as
the lesions grow older. Yellow streaks
may extend from the lesions to the tip
of the leaf, covering the entire length
of the leaf blade. The lesions then turn
reddish brown and the streaks become
orange or rusty in color. The whole
leaf mass eventually become necrotic.
Old lesions often become gray at the
center. At the early flowering stage,
the lesions occur more frequently on
the lower leaves and at the flag leaves,
and on the other young leaves at the
ripening stage. So far, the etiology of
the disorder has not been established.
There were some indications that this
may be a complex disease, resulting
from an interaction between soil
fertility and a weak pathogen. Work in
IRRI is now focused on establishing the
etiology of the disease.

Quick Genomic DNA Micropreparation
from Rice-Pathogenic Xanthomonads.
R.P. Scott, R.J. Nelson and R.S.
Zeigler. IRRI, College, Laguna.

A fast and inexpensive
micropreparation of DNA without
organic extraction for routine Southern
blot hybridization was developed for
the pathogenic bacteria, Xanthomonas
oryzae var. oryzae and X. oryzae var.
oryzicola, causing foliar blight and
streak diseases in rice, respectively.
The procedure took advantage of the
selective removal of proteins and
polysaccharides as co-precipitants of
potassium dodecyl sulfate. The
inclusion of detergent in the extraction
buffer and the removal of RNA through
direct RNAse treatment of cell lysates
further simplified the extraction

Philipp. Phytopathol. 1994, Vol. 30(2):122-143

process. The protocol yielded high-
quality DNA which can be cut readily
with BamHI, EcoRI, Mspl, Pstl, and
Sail, and it could be applicable to other
gram-negative bacteria. The
convenience of processing a hundred
bacterial samples in half a day made
the procedure attractive for population
level studies.

Inheritance of Resistance to Rice
Tungro Spherical Virus in Rice. L.A.
Ebron, R. Ikeda, T. Imbe, R.R. Yumol,
N.S. Bautista and M.J.T. Yanoria. IRRI,
College, Laguna.

The genetics of resistance to
infection by rice tungro spherical virus
(RTSV) in resistant cultivars Utri
Merah, Utri Rajapan and Pankhari 203
was studied. The F1 and F3 progenies
of crosses between resistant cultivars
and susceptable cultivars (Taichung
Native 1 (TNI) or IR22), were tested to
determine the mode of inheritance for
resistance to RTSV. The allelic
relationships of resistance genes
among the resistant cultivars were also

Utri Merah is found to possess 2
independent recessive genes for RTSV
resistance. Resistance in Pankhari 203
and Utri Rajapan is supposed to be
under monogenic control. Allelic tests
among three resistant cultivars
segregated no susceptible F3 lines
indicating that all the cultivars
possessed the same or closely linked

Therefore, we propose gene
symbol, tsv-1, for RTSV resistance
gene, in Utri Merah, Utri Rajapan and
Pankhari 203, and tsv-2 for another
RTSV resistance gene in Utri Merah.

Philipp. Phytopathol. 1994, Vol. 30(2):122-143

Analytical Study Of Seed-Borne Fungi
Associated With Rice For The Last Ten
Years In The Philippines (1983-1993).
J.S. Bartolini, E.G. Sison and E.P.
Sevilla. BPI, Manila.

Data on percentage frequency of
the different seed-borne fungi
associated with rice for the last ten
years at the Seed Health Laboratory,
BPI, Manila were statistically analyzed
using Least Square Difference (LSD).

Fungal species isolated using the
blotter test with their frequencies for
the past ten years are the following:
Trichoconis padwickii (1964),
Aspergillus flavus (670), Curvularia
lunata (563), Fusarium moniliforme
(463), Verticillium sp. (338),
Cephalosporium sp. (281), Aspergillus
sp. (258), Penicillium sp. (187),
Curvularia sp. (169), Phoma sp. (143),
Fusarium semitectum (24) and
Drechslera sp. (8).

Results showed that the frequency
of each pathogen varies significantly
from year to year.

Oryza Glaberrima as an Indicator Plant
for Rice Tungro Viruses. P.O.
Cabauatan, N. Kobayashi, R. Ikeda and
H. Koganezawa. IRRI, College, Laguna.

Oryza glaberrima (IRGC Acc. No.
100139) was identified and evaluated
as an indicator plant for rice tungro
viruses (RTVs). This accession was
evaluated for its sensitivity to infection
with RTVs, susceptibility to both virus
and vector, and suitability as virus

IRGC 100139 was not only
susceptible but also very sensitive to
infection with RTVs. When inoculated
at seedling stage with rice tungro
spherical virus (RTSV), a latent virus,
infected plants showed stunting,

reduced tillering and pale green leaves
3-4 weeks after inoculation. Visual
score based on these symptoms was
highly accurate when compared with
serological score. This accession could
also be used to distinguish plants
infected either with rice tungro
bacilliform virus (RTBV) alone or with
both RTBV and RTSV. Generally,
plants infected with both viruses died
within three weeks of inoculation while
those infected with RTBV alone
survived beyond three weeks but died
before maturity. Similar symptoms
were observed when this accession
was inoculated by leafhoppers
collected from the field for monitoring
viruliferous insects. Visual score based
on symptom severity and life span of
infected plants correlated well with
serological score. IRGC 100139 was
also susceptible to the leafhopper
vector Nephotettix virescens
comparable to rice cv Taichung Native
1. It was also a good virus source.
Hence, this accession has the
attributes of an ideal indicator host and
it would be useful in studying the
epidemiology of rice tungro disease
without the need for expensive
serological assays.

New Alternate Hosts Of Banana
Bunchy Top Virus (BBTV). A.A.
Eusebio and N.B. Bajet. UPLB, College,

New alternate host of banana
bunchy top virus (BBTV) were
established using the aviruliferous
Pentalonia nigronervosa allowed to
acquire the virus for 24 to 48 hours
from the BBTV-ELISA positive Musa
spp. (Sexy Pink or SP). The putative
BBTV in naturally infected Orange
Blossom (OB) can infect abaca (Musa
textilis 51 and 52) and banana
(Lakatan). Likewise, BBTV in SP can be
transmitted to SP and abaca. The
symptoms induced by BBTV in

inoculated OB and SP plants were
yellowing of leaf edges and margins,
discontinuous streaks and mild to
severe mosaic. The BBTV was
transmitted from abaca to abaca, to
banana and to OB. The transmission of
BBTV from abaca to banana (varieties:
Giant Cavendish, Lakatan and
Latundan) and the positive reaction of
bunchy top infected abacas to the anti-
BBTV antibodies suggest that BBTV
and ABTV is one and the same or very
closely serologically related viruses
that infect Musa spp. The bunchy top
virus of abaca was reported by other
investigators to infect only abaca but
not banana while the virus infecting
banana can infect both abaca and
banana. The transmission of BBTV in
abaca to OB showed that the virus
infects another member of Musa family
aside from the cultivated banana and
abaca plants. Field collected BBTV
which served as the positive check for
transmission experiment was
consistently transmitted to banana and
abaca. The symptoms expressed by
the putative BBTV in these hosts
initially appeared as dotlike that later
coalesced to form streaks in the
youngest expanded leaf of the
inoculated plants. The unfurled leaves
showed yellowing on leaf
edges/margins leaving the midrib
unaffected by this color change. As
the disease progressed, leaves that
developed are chlorotic, reduced in
size, and are bunched together in
nearly one level showing the
characteristic bunchy top virus

Cadang-Cadang Disease Incidence in
the Philippines. A.R.R. Alfiler and E.P.
Pacumbaba. PCA, Albay.

Incidence of cadang-cadang, a
lethal disease of coconut in south-
eastern Luzon, Philippines continued to
decline in recent years. Results of

Philipp. Phytopathol. 1994, Vol. 30(2):122-143

recent surveys showed that there were
145,000, 145,000 and 192,000
estimated new cases of cadang-cadang
in 1984, 1986 and 1990, respectively.
However, the number of palms lost to
the disease is still substantial
considering that coconut is an
important subsistence and a major
cash crop in the Philippines.

Immunosorbent Electron Microscopy
for Detection of Tungro Viruses in
Crude Sap of Infected Rice. F.C. Sta.
Cruz, E.R. Tiongco and H.
Koganezawa. IRRI, College, Laguna

The immunosorbent electron
microscopy (ISEM) technique was
optimized to detect rice tungro
bacilliform virus (RTBV) and rice tungro
spherical virus (RTSV) using crude sap
from tungro-susceptible cultivar
Taichung Native 1. This technique then
was used to detect RTBV in tungro-
tolerant cultivar Utri Merah. Copper
mesh grids were floated on a drop of
virus antibody (1 ug/ml or 10 ug/ml for
RTBV 1gG and 5 ug/ml or 20 ug/ml for
RTSV 1gG) and washed with
phosphate buffer saline plus bovine
serum albumin. The grids were floated
on a drop of crude sap of 1:10, 1:100,
1:1000, and 1:10,000 dilutions,
washed and stained with 2% uranyl
acetate, and observed in a Philips 410
transmission electron microscope.
RTBV and RTSV were detected in TN1
at different dilutions of crude sap of
infected plants. At 10 dilution,
particles of both RTBV and RTSV were
still detectable by ISEM but not by
enzyme linked immunosorbent assay
(ELISA). There was no significant
difference on the number of virus
particles adsorbed on grids between
low and high concentrations of virus
antibody. Very few particles were
observed on grids which were not
incubated in the tungro virus antibody.
Of 22 samples tested for Utri Merah,

Philipp. Phytopathol. 1994, Vol. 30(2):122-143

ISEM detected RTBV in all samples
while ELISA detected RTBV in 17
samples indicating higher sensitivity of
ISEM over ELISA. However, ISEM is
not suitable for testing a large number
of samples.

Association of Protein of Rice Tungro
Bacilliform Virus to Virions. M.L.M.
Yambao, Z.M. Flores, F.C. Sta. Cruz
and H. Koganezawa. IRRI, College,

Rice tungro bacilliform virus, a
member of badnavirus, encoded
proteins with molecular weights of
24k, 194k, and 46k. 194k polyprotein
encoded the coat proteins, viral
proteinase, reverse transcriptase, and
ribonuclease H. The functions of the
other proteins were still unknown. To
examine the function of 12k protein
(pl 2), the anti antiserum was raised by
injecting rabbits with synthetic peptide
covering the 16 amino acids of the N-
terminus. Immunoblotting using the
antiserum revealed the presence of in
partially purified and purified virus
preparations but not in the crude
extracts of infected plant and healthy
plant controls was not detected when
polyclonal antibodies against the virus
(purified using driselase) were used.
This means that was lost during the
driselase treatment in addition to the
major coat protein, is probably a
constituent of the viral capsid. The
results suggest that may play a role
similar to that of the gene III product
of caulimoviruses.

Concentrating Genes For Downy
Mildew Resistance and Desirable
Agronomic Traits In Corn. A.D.
Raymundo and B.J. Calilung, Jr. UPLB,
College, Laguna.

Following a simple phenotypic
recurrent selection technique, two corn

populations which are highly resistant
to Peronosclerospora philippinensis
(Weston) Shaw, the causal pathogen
of Philippine downy mildew, were
developed. These populations,
designated as CPRP1 and CPRP3, were
from base populations earlier formed
out of the resistant plants of the F2
generation of commercially available
hybrids. After several cycles of
selection under high inoculum
pressure, a significant increase in the
level of resistance was observed in
both populations when compared to
the reaction of the original F2
populations. As each population is
highly diverse genetically, visual
selection for agronomic characters,
such as plant height, ear height,
general vigor, ear size, and tassel size,
was likewise done. Selection for
resistance to other pathogens that
attack the crop at subsequent stages
of growth is possible in these

Spatial Structure of Natural Epidemics
of Sheath Blight of Rice. A.D.
Raymundo, N.G. Fabellar and P.S.
Teng. IRRI, College, Laguna.

Incidence of sheath blight cause
by Rhizoctonia solani in rice cultivar,
PSB Rc2 in two farmers' fields in Pila,
Laguna was recorded for a period of
eight weeks starting at maximum
tillering stage in an attempt to monitor
the progression of naturally occurring

Sheath blight infection was
common in both fields. In the first plot
in barangay San Antonio where
disease distribution was uniform,
approximately 25% of the hills showed
symptoms during the first reading at
55 days after transplanting and
increased to 100% infection six weeks
after. There was an aggregate pattern
of disease dispersion in the second

plot. During the initial reading at 35
days after transplanting, symptoms
were seen in 15 percent of the hills.
Eight weeks later, disease was
observed in 80% of the hills. Initial
geostatistical analysis indicated that
variability in patterns among diseased
plants was random and not influenced
by spatial dependence among
neighboring hills.

Control of Hirschmanniella oryzae
Using Sesbania rostrata and its
Residual Effects in a Continuous Rice
Cropping. I.R.S. Soriano, D.M. Matias
and Jean-Claude Prot. IRRI, College,

A four continuous cropping
experiment was conducted to
determine if the yield increase in rice
could be attributed to the decrease in
Hirschmanniella oryzae population
when grown in a sequential cropping
with Sesbania rostrata, and if there is a
residual effect of the treatment on
subsequent rice crops. The treatments
included the growing of S. rostrata and
rice during the first cropping and
incorporation of the legume before the
second rice crop. Carbofuran was
added to the same set of treatments
for comparison. A 30-45% yield
increase of the first rice crop was
observed when S. rostrata was grown
regardless of incorporation as green
manure and in all treatments with
carbofuran. A significant correlation of
yield and nematode population
densities was also observed. A 16-
25% increase in yield was observed in
treatments with carbofuran after the
second rice crop and a significant
correlation with nematode population
after the third rice crop. The increase
in rice yield, therefore, could be
attributed not only to the fertilizer
effect brought about by growing of S.
rostrata or green manure application
but to the control of the rice root

Philipp. Phytopathol. 1994, Vol. 30(2):122-143

nematode. The treatments were
effective in 2 rice croppings only after
growing of S. rostrata and/or
incorporation as green manure.

Decomposers In Mount Pangasugan.
R.M. Gapasin, J.L. Lim, M.J.C. Ceniza.
ViSCA, Baybay, Leyte.

Eleven insect and three arachnid
orders were collected and identified.
Among the insects, the Collembolans
ranked first but their population was
much lower compared to the mites
(Order Acarina) which have the highest
population (60.26%) among the
arthropod decomposers. Other
arthropods associated with
decomposing litters belonged to the
orders Diptera, Coleoptera, and

Arthropod decomposers were
most abundant after two months with
an average decomposition of 51.98%.
Macro-climatological parameters did
not affect their population. Litter
weight loss increased with the length
of exposure to decomposers.

Fifteen (60%) fungi and 6 (40%)
bacteria were isolated from soil and
leaf litters. Decomposing ability of the
fungal isolates ranged from 12-30%.
The different isolates colonized the
substrate in 4-25 days.

The Use of 32P-labelled Nucleic Acid
Probes for Sensitive and Specific
Detection of Coconut Cadang-Cadang
Viroid (CCCVd). Ma. J. B. Rodriguez.
PCA, Albay.

The conditions that assure high
sensitivity, specificity and reliability of
P-labelled probes in hybridization
assay for CCCVd were determined.
Two types of probe were prepared,
namely complementary DNA (cDNA)

Philipp. Phytopathol. 1994, Vol. 30(2):122-143

probe synthesized by primer extension
on purified CCCVd246 and cRNA
probe was prepared by in vitro
transcription of the CCCVd246 insert
in a pSP64 plasmid. These probes gave
nearly the same sensitivity in several
tests done with a detection limit of
approximately 2 pg. Their specificity to
CCCVd was likewise assessed by
comparing results of dot-blot and
northern-blot hybridization of the
probes to other nucleic acids present in
the samples was distinguished and
appropriate steps to eliminate this
problem were incorporated in the

Nucleic acid hybridization has
recently been the method of choice
worldwide for routine indexing of plant
pathogens. Previous methods are
either not sensitive enough or
inadequate for large-scale testing.

Direct Tissue Blotting for Detection of
Rice Viruses. G.J. Miranda and H.
Koganezawa. IRRI, College, Laguna.

Direct tissue blotting method was
used field detection of rice viruses

(RTSV), rice grassy stunt virus such as
rice tungro bacilliform virus (RTBV),
rice tungro spherical virus (RGSV), and
rice ragged stunt virus (RRSV). Rice
plant parts, culm, sheath, and leaf,
were cut by a razor blade. The cut
surface was directly blotted by
pressing it gently onto a 0.45 um pore
size nitrocellulose membrane. Signal
for virus infection was detected using
direct and indirect immunoblotting. Of
the three tissues, the sheath samples
gave the best signal. The indirect
method is more sensitive than the
direct one in detecting all viruses.
Optimum dilutions of immunoglobulin
(1gG) for the indirect method were
1/4000 for RGSV and 1/1000 for
RTBV, RTSV and RRSV. After adding
the substrates, initial reaction started
within 15-30 min for RGSV and 30-45
min for RTBV, RTSV and RRSV. The
whole procedure took 4 to 5 hr. The
results showed that tissue blotting is
specific, sensitive, rapid, and is a
convenient method to assay a large
number of samples. Most serological
diagnostic methods for plant viruses
require extraction of plant sap which
limits its use in the field.


1. Membership in the Philippine Phytopathological Society is prerequisite to publish-
ing in Philippine Phytopathology or at least one author must be a member of this
society. The Editorial Board, however, may relax this rule in the case to contribu-
tions of exceptional merit. It may also invite distinguished scientists to contribute
articles of interest to the Society.

2. Manuscripts must be reports of original research, except meritorious reviews, and
should have not been published elsewhere. The decision of the Editorial Board to
accept or reject the manuscript is final.

3. The manuscript should be typed on one side of 81 x 11 inch paper, double spaced

4. The author's name should follow the title. Author's position and institutional ad-

5. Papers other than Notes may be organized conveniently under: Abstract, Introduc-
tion, Materials and Methods, Results, Discussion, (or Results and Discussion) and
Literature Cited.

6. In the text, citations shodlld be by name-and-number system, e.g. Ou and Nuque (1).
With 3 or more authors, use et al. (e.g. Ou, Nuque and Silva (1) should appear Ou,
et al. (1); the number in parenthesis should correspond to the number of the article
cited (or referred to in the text) under literature cited.

7. Literature citation should be in alphabetical order and with numbers. Do not cite un-
published work; it should appear as footnote. Biological Abstracts' 1968 List of
Serials with Title Abbreviations must be consulted in abbreviating the names of
journals. Examples of abbreviation: Philipp. Entomol., Philipp. Phytopathol., J.
Mol. Biol., Plant Dis. Reptr., J. Agr. Res., Amer. J Bot.

8. Acknowledgements should be placed at the end of the article i.e. after Literature

9. Tables should be numbered consecutively, and each typed on a separate page. They
must have descriptive headings and should be understandable without reference to
the text. Lower case superscript letters are to be used for footnotes to tables. Pages
containing tables should follow Literature Cited and should be numbered accord-

10. Figures should add clearly to an understanding of the paper. The size and arrange-
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and author's name. Legends for figures should be typed together on a separate num-
bered page following the tables.

11. See latest journal of Philippine Phytopathology for more details on the format of
papers to be submitted to the journal.

12. Articles published are not paid but authors foot the bill for reprints

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