BIBLIOGRAPHY PATRICIO, JOEYLITO G....
BIBLIOGRAPHY
PATRICIO, JOEYLITO G. APRIL 2011. Incidence and Severity of Squash Leaf Curl
Virus Infection on Chayote in La Trinidad, Tublay and Atok, Benguet. Benguet State University,
La Trinidad, Benguet.
Adviser: Julio S. Ligat, Ph.D.
ABSTRACT
This study was conducted to assess the incidence and severity of Squash Leaf Curl Virus
on Chayote in La Trinidad, Tublay and Atok, Benguet.
Results in the greenhouse experiment revealed that the municipality of Tublay had the
lowest Squash Leaf Curl Virus local lesion and systemic severity. The Municipality of Atok and
La Trinidad had the highest disease severity.
In the field survey, the chayote plantation in Tublay, Benguet had the lowest Squash Leaf
Curl Virus disease severity and disease incidence. The Municipalities of Atok and La Trinidad,
Benguet had the highest of disease severity and disease incidence of Squash Leaf Curl Virus.
TABLES OF CONTENTS
Page
Bibliography...……………………………...................................................... i
Abstract ……………………………………………………………………….. i
Table of Contents ………………………………………………………….... ii
INTRODUCTION……………………………………………………………. 1
REVIEW OF LITERATURE………………………........................................ 4
About the Disease……………………………………………………… 4
Virus Symptoms………………………………...................................... 4
Transmission of Viruses………………………........................................ 6
MATERIALS AND METHODS……………………………………………… 8
Survey of Squash Leaf Curl on
Chayote……………………………….................................................... 8
Mechanical Transmission of
Squash Leaf Curl Virus ………………………………………………… 8
Data Gathered…………………………………...................................... 12
RESULTS AND DISCUSSION……………......................................................... 14
Visual Symptoms of Squash
Leaf Curl Virus on Chayote………………………………………………. 14
Severity of Squash Leaf Curl
Virus of Chayote in the BSU
Greenhouse…………….............................................................................. 15
Field Survey on the Severity
and Incidence of Squash Leaf
Curl Virus……………………...................................................................... 18
SUMMARY, CONCLUSIONS AND RECOMMENDATIONS……................. 20
Summary……………………………………………................................... 20
Conclusions……………………………………………………………….. 20
Recommendations…………………………………………........................ 20
LITERATURE CITED…………………………………………………………… 22
APPENDICES……………………………………………………………………. 24
1
INTRODUCTION
Chayote (Sechium edule) is a perennial, training vine bearing edible fruits which
belong to family Cucurbitaceae. Knot and Deanon (1980) stated that the chayote is a
nature of Mexico, Central America and the West Indies.
Chayote and other crops belonging to the Cucurbit family are given on overhead
trellis (Knot and Deanon, 1980). In addition, side trellis is used to withstand strong wind
in wind prone areas. This practices combined with judicious pruning will enhance more
yield for the crop. If they reach the desirable size, they are harvested manually (Velasco,
1994).
The symptoms exhibited by a virus infected plant may be due to other factors
such as mineral deficiency, insects, nematodes, fungi and other environmental factors.
But, oe of the many ways to determine virus infected plant is the shortening of internodes
(Bawden, 1964) and curing of leaves.
Virus is one of the pathogen that is difficult to control because it is highly
dependent on the disseminating agents such as insects. In addition, viruses could also be
transmitted mechanically by the use of contaminated garden tools of manual handling of
plant part by man.
The squash leaf curl virus affects most cucurbits, with cucumber showing the
least symptoms. Leaves are cupped upward, new growth bends upward, and mid-vein
portions of leaves are severely mottled. Flowers and fruit are small and abnormally
developed. Control measures focus on lowering the potential virus inoculums in the area.
These measures include that weeds around the fields do not harbor whiteflies and destroy
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
2
infected crops as soon as practical after harvest. Controlling the whiteflies directly has
not proved successful (Horn et al., 2004)
Squash leaf curl is transmitted persistently by both biotypes of the sweetpotato
whitefly, Bemesia tabaci. It has been a problem in Arizona in fall watermelons in the
central part of the state. Infection of young plants causes severe curling, and small leaves
that are mottled and yellowing. Often an entire field may be affected, but young plants
have been seen to grow out of the disease. It occurs primarily in squash and watermelon.
No resistant varieties are known, but a host free period with sanitation and weed control
may reduce subsequent infections.
Like in most municipalities of Benguet, vegetable farming is one of the sources of
livelihood among the municipality population of La Trinidad, Tublay and Atok. Chayote
is raised throughout the year and is preferred by farmers of Benguet because it is easy to
sell at local and city markets.
At present, one of the problems faced by farmers in growing chayote is the
incidence of disease exhibiting the upward cupping of leaves bending of new growth
upward, and severe mottling of the mid-vein portions of leaves. No management
strategies are being employed for these disease infections. Thus, information on the
disease characteristics like incidence and severity would be of great help to the chayote
farmers of La Trinidad, Tublay and Atok, Benguet.
The study aims to assess the incidence and severity of squash leaf curl virus
infection on chayote La Trinidad, Tublay and Atok, Benguet.
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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The survey was conducted in selected existing chayote plantation at La Trinidad, Tublay
and Atok, Benguet. The mechanical transmission activity was conducted in the Plant
Pathology Greenhouse, College of Agriculture, Benguet State University, La Trinidad,
Benguet.
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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REVIEW OF LITERATURE
About the disease
Squash leaf curl virus (SLCV) was detected for the first time in Jordan using
degenerated oligonucleotide primers. Two isolates of the virus, SLCV-E and SLCV-R,
were detected using specific oligonucleotide primers in symptomatic Cucurbita pepo.
SLCV was also found to occur naturally in Malva parviflora, which showed severe leaf
curling, yellowing and stunting of the whole plants. The full-length genomes of Squash
leaf curl virus-Malva (SLCV-Malva) isolate were amplified using the bacteriophage Φ
DNA polymerase enzyme. Nucleotide sequence analysis showed that SLCV-Malva
shared high nucleotide identity (98% and 97%) with SLCV-EG and SLCV-E from Egypt
and USA, respectively. A survey using dot-blot hybridization indicated that squash leaf
curl disease occurred in all surveyed areas. The highest disease incidence (95%) was
recorded in Dir Alla area, whereas disease incidence did not exceed 69% in squash
samples collected from North Ghor (Al_Muza, 2007).
Virus Symptoms
Diener (1967) as stated by Singh (1978) cited that infected plants show
histopathology changes as hyperthrophy, hyperplasia, and necrosis. The physiology of
the plant is affected as shown in the decreased photosynthetic activity, increased activity
of phenophenoloxides and accumulation of oxidized polyphenol derivatives and
increased activity of growth regulating substances.
Janick (1972) as cited by Angadol (1983) grouped the virus diseased into two;
the yellow viruses and mosaic viruses. Symptom of the yellow viruses include yellowing,
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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leaf curling, dwarfing, excessive branching, shortening of the mosaic viruses includes a
mosaic appearance and mottling which is due to chlorosis in small areas of the plant
following the death of the tissues.
Smith (1972) as cited Angadol (1983) mentioned that in the field, infected plants
are readily recognized by their reduced size and different growth habits and by marked
changed in leaf color and shape, flower buds are killed and reduced yields are obtained
when infection occurs before motivation of plants or fruits.
Tarr (1972) as cited by Angadol (1983) stated that symptoms of virus diseases in
plants are varied, often severe and sometimes so slight that it cannot be noticed
immediately except on close examination. Symptoms may disappear under certain
environmental conditions such as high temperature, or following the application of
certain fertilizers. Some plants may show no outward symptoms even if they contain the
virus.
Singh (1978) also mentioned that plant viruses are infections and sometimes
highly contagious. However, Mathews (1981) mentioned that virus infections do not
necessarily caused disease at all times in all parts of an infected plants. There are at least
five (5) situations in which disease may be absent. They are, infection with a very mild
strain of the virus; a tolerant host, nonsterile “recovery” from disease symptoms in newly
formed leaves; leaves that escape infection because of their age and positioned in the
plant; and dark green areas in a mosaic pattern.
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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Transmission of Viruses
One of the cardival characters of a virus is the fact that it has infections. However,
it was recognized early, that viruses differ widely in the means and in the ease with which
they may be transmitted. Some can be transmitted easily while others are difficult to
transmit by artificial means. Some viruses have been transmitted by only one method
while others are has been transmitted by two or more methods. This was brought about
by the coincidence that the two viruses studied first, peach yellow and tobacco mosaic
represents extremes. The common tobacco mosaic virus is transmitted readily by simple
mechanical means, while peach yellow virus is transmitted by us of buds and graft.
As cited by Ilag (1987), viruses are transmitted by mechanical means, by
nematodes, by certain soil-borne fungi, by mites, through infected seeds and through
infective vegetative planting materials.
Moreover, Singh (1978) further stated other means through which virus can be
transmitted by vegetatively reproductive parts, transmission by grafting and budding,
transmission of viruses by pollen, transmission by seed, transmission of viruses through
weeds and flowering plants parasites, transmission of viruses through insects and
transmission by contact of diseased plant and healthy plants.
The same author further stated that the insects can transmit only one specific virus
to only one species of the host plant while other transmit as single virus to more than one
species of the host.
Walker (1969) reported that viruses which are readily more transmitted
mechanically are aphids and those which do not yield to such transfer are leaf hopper-
borne. Furthermore, there are differences among vectors and their relation to the virus
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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they transmit. Some viruses transmitted by aphids and whiteflies are carried in such a
way that the vectors remain viruliferous for a period of only a few minutes to a few
hours. These virus as cited by Ligat (1983) are called stylet-borne viruses. The same
species of aphids and whiteflies may transmit the virus after several hours after it is
possible that the virus infected by the insects is later transmitted through the body into the
saliva, by which channel it eventually reaches the next host plant.
Ilag (1987) also reported that viruses are transmitted mechanically. Bawden
(1964) stated that the many reported failures to infect plants in mechanical transmission
by inoculation with extract from infected ones, reflect the intrinsic behavior of the
infective virus is doubtful. He further stated that the failures most probably occurred
because the properties of either the plant yielding the extract or the one inoculated
prevented infection. Moreover, virus inoculum containing adequate concentration of
virus, transmission and deposition of virus through abrasive (such as carborandum)
causing injuries on the plant, and establishment of infection by placing the polycestronic
viral genome first, are the factors essentially for mechanical transmission.
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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MATERIALS AND METHODS
Survey of Squash Leaf Curl Virus on Chayote
A survey and documentation of the incidence and severity of Squash Leaf Curl
Virus infection on chayote was done at the selected municipality of La Trinidad, Tublay
and Atok, Benguet. From the selected sites samples of infected leaves with SLRV, were
gathered and was used for inoculation at the greenhouse of BSU.
Mechanical Transmission of Squash Leaf Curl Virus On Chayote
1. Source of samples. Leaves suspected of being infected with Squash Leaf Curl
Virus were collected in existing chayote farms in the municipality of La Trinidad, Tublay
and Atok, Benguet.
2. Preparation and inoculation of test plants. Previously germinated seedlings of
Vigna umbellate were used as indicator plant in the study. This plant was used because; it
showed prominent manifestation of Squash Leaf Curl Virus symptoms (Cohen et al.
1983). The seedlings were transplanted in black plastic bags. The seedlings at four to six
leaf stages were used as test plants.
3. Mechanical Transmission experiment. Prior to bioassay, suspected Squash Leaf
Curl Virus infected chayote leaf samples were weighed to determine the amount of
phosphate buffer that was added. The sap was extracted with the use of mortar and pestle.
Before inoculation, the upper left surface of test plants was dusted with carborundum
powder # 320. Sap inoculation was done by dipping the forefinger into the pestle
containing the mixture of sap and buffer and then rubbing it gently on the carborundum-
dusted leaves. After inoculation, the inoculated leaf surfaces were washed with distilled
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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water to remove carborundum dust. Each test plants were labeled properly. Inoculated
test plants were incubated inside the greenhouse and then observed for reactions daily for
three weeks. Photographs of the plants showing symptoms were taken.
Figure 1. Map of the surveyed sitios in La Trinidad, Benguet
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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Figure 2. Map of the surveyed sitios in Atok, Benguet
Figure 3. Map of surveyed sitios in Tublay, BengueT
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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Figure 4. Mechanical transmission activities in the greenhouse
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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Data Gathered
1. Severity of Squash Leaf Curl Virus on Chayote
A. Green House
The number of necrotic spots on the inoculated Vigna umbellata (as test plants),
were assessed using the arbitrary rating scale below (Ligat and Lumiqued, 2000).
Scale Description
0
No infection
1
Mild infection, 1-10 necrotic spots in
inoculated leaf, local infection.
3
Moderate infection, 11-25 necrotic spots in
inoculated and uninoculated leaf, systemic
infection
5
Severe infection, 26-50 necrotic spots in
inoculated and uninoculated leaf, systemic
infection.
Disease severity will be expressed
DS = n (0) + n (1) + n (3) + n (5) x 100
N x5
Where:
n- Number of necrotic spots classified by scale.
N- Total number of sample plants
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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B. Field Condition
Twenty plants were selected per surveyed area and rated for disease severity. The
severity was assessed using the arbitrary rating scale below (Ligat and Lumiqued, 2000).
Scale Description
0
No infection
1
Mild infection, 1-10 infected leaves per
plant.
2
Moderate infection, 11-25 infected leaves
per plant.
5
Severe infection, 26-50 infected leaves per
plant.
Disease severity will be expressed as:
DS = n (0) + n (1) + n (3) + n (5) x 100
N x5
Where:
n = number of infected leaves per plant classified by scale.
N = total number of plants
3. Incidence of Squash Leaf Curl Virus on chayote. The presence or absences of
Squash Leaf Curl Virus - infected chayote plants were recorded. The datum was
determined by dividing the number of infected plants over the total number of sample
plants multiplied by 100.
4. Location map showing the different sites.
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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RESULTS AND DISCUSSION
Visual Symptoms Of Squash
Leaf Curl Virus on Chayote
Infected leaves are frequently puckered and mottled yellow or light green leaf
symptoms are more evident on younger leaves (Figure 5). Plants can be stunted (Figure
6) especially when the infection occurs early in the development. Although infected fruit
can be reduced in size and show variation in colors, the most obvious symptoms is
distorted or lumpy appearance (Figure 7).
Figure 5. Leaf stunting on Chayote caused by SQLV
Figure 6. Stunting of young Chayote caused by SQLV
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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Figure 7. SQLV symptoms on Chayote
Severity of Squash Leaf Curl Virus
on Chayote in the Greenhouse
Squash Leaf Curl Virus infected chayote leaf samples from the three
municipalities were transmitted mechanical to Vigna umbellate which served as indicator
plant in the greenhouse. Six days after inoculation, local lesions were recorded in
infected samples from Tublay, which had the lowest disease infection (Table 1). The
Municipality of Atok and La Trinidad had the highest disease severity of 70.34 and 68.66
percent.
Twelve days after inoculation (Figure 10), the disease infection became systemic
where infection exhibiting necrotic lesions after six days of inoculation. This was
observed in the samples from Tublay municipality which had the lowest Squash Leaf
Curl Virus severity and in Atok and La Trinidad which registered the highest of 68.33
and 58.66 percent.
It could be noted from the results that there was a virulent strain of Squash Leaf
Curl virus in Tublay, Benguet. Another implication could be the phenomenon of Squash
Leaf Curl Virus latent infection in Atok and La Trinidad, Benguet.
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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The Chayote plantation in Ambassador, Tublay, Benguet were intercropped with
a tree (alnus), trumpet flower and flower of the night or “Dama de Noche” which are
non-hosts of Squash Leaf Curl Virus.
The presence of alnus trees may have resulted to the low the Squash Leaf Curl
Virus in Tublay which conforms with the findings of Ligat (2004) that alnus trees
enhanced growth vigor of chayote and develop resistance against Squash Leaf Curl due
to the nitrogen-fixing capacity of alnus species, saturated by light of one-tenth the higher
intensities which increases photosynthetic rate it also releases low molecular weight
substances from decayed debris which taken up by chayote resulting to an increased
metabolism and influence development of resistance against the virus disease.
Table 1. Severity of squash leaf curl virus in the BSU (Greenhouse Experiment)
SOURCE OF INOCULUM LOCAL LESION SYSTEMIC INFECTION
La Trinidad 68.66 58.66a
Tublay 57.67 39.00b
Atok 70.34 68.33a
Coefficient of Variation 27.14% 27.35%
Means followed by common letters are not significantly different at 5% level DMRT
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
17
a b c
Figure 8. Samples of Vigna umbellate as indicator plant (Internet) (a. uninoculated
b. necrotic lesion, c. systemic infection)
a
b
Figure 9. Samples of Vigna umbellate as indicator plant (Present study) a. uninoculated
b. inoculated
Figure 10. Systemic infection of SQLV after 12 days of inoculation
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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Field Survey on the Severity and Incidence
of Squash Leaf Curl Virus
The Chayote plantation in Tublay, Benguet had the lowest Squash Leaf Curl
severity which had comparable results with the chayote plantation in Atok, Benguet
(Table 2, Figure 11 and 12). The highest disease severity was observed in La Trinidad,
Benguet (Figure, 13).
Tublay, Benguet (Figure 12) had the lowest incidence of Squash Leaf Curl Virus
and La Trinidad municipality (Figure 13) had the highest disease incidence.
The Chayote plantation in La Trinidad, Benguet had abundant wild sunflowers
around the vicinity of the farm which provided a haven for whiteflies which is a vector of
the virus. The surrounding was also covered with lime stones which emit heat and
enhance the dryness of the plantation making conditions favorable for whiteflies
population increase.
Table 2. Severity and incidence of squash leaf curl virus in the field
SOURCE OF INOCULUM SEVERITY INCIDENCE
La Trinidad 54.25 50a
Tublay 47 46.25a
Atok 47.27 48.75a
Coefficient of Variation 8.36% 18.33%
Means followed by common letters are not significantly different at 5% DMRT
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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Figure 11. Chayote plantation in Atok, Benguet which had the lowest systemic
Symptom of SQLV
Figure 12. Chayote plantation in Tublay, Benguet which had the lowest local lesion
Smptom of Squash Leaf Curl Virus severity
Figure 13. Chayote plantation in La Trinidad, Benguet which had the highest
Symptom of Squash Virus severity and incidence
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
20
SUMMARY, CONCLUSIONS AND RECOMMENDATIONS
Summary
This study was conducted to assess the severity and incidence of Squash Leaf
Curl Virus on chayote in La Trinidad, Tublay and Atok from August to March 2011.
In the greenhouse study it was noted that six days after inoculation, the
representative test plants of Tublay had the lowest number of necrotic spots while the
more necrotic spots were observed in plants inoculated with samples from Atok and La
Trinidad. Twelve days after inoculation, systemic infection was noted where samples
from Tublay had the lowest infection and in Atok and La Trinidad with the highest
infection.
In the field survey, the chayote farm in Tublay had the lowest severity and
incidence of SQLV and the highest was observed in La Trinidad. Incidence of the virus in
La Trinidad and Atok was 100%.
Conclusions
Based on the results, the incidence and severity of SQLV infection on chayote in
La Trinidad, Tublay and Atok, Benguet ranged from 47% to 100%. SQLV is transmitted
by whiteflies but can also be mechanically transmit.
Recommendations
It is recommended that farmers should take precautions in obtaining chayote
planting materials from La Trinidad, Tublay and Atok as there were high severity and
incidence of Squash Leaf Curl Virus. Further, farmers should initiate proper care and
control measures not to spread the virus as it could be mechanically transmitted. Field
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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sanitation should be observed by farmers in order to prevent the proliferation of
alternative hosts and white flies as vector of the disease.
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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LITERATURE CITED
AGRIOS, G. N. 1997. Plant Pathology. 4th ed. New York: Academy Press. Pp.
479-490.
AL MUZA, A. 2007. Detection and Molecular Characteristics of Squash Leaf Curl Virus
(SQLV) in Jordan, Departmen t of Plant Protection, Faculty of
Agriculture, University of Jordan, Amman, Jordan.
ANGADOL, P. P. 1983. A survey on the incidence and identification of virus symptoms
on the Important flower in Benguet . BS Thesis. BSU, La Trinidad,
Benguet. P.1.
BATNAG, A.G. AND J.S. LIGAT. 1996. Symptomatology and sap transmission of virus
like diseases of chayote in Benguet and Baguio City, BS Thesis. Benguet
State University, La Trinidad, Benguet.
BAWDEN. F. C. 1964. Plant virus disease. 4th New York; Ronald Press Co.
P. 97.
BOGSULEN, R. A. 1996. Ocular survey on the incidence of virus-like disease affecting
Chayote in Benguet and Baguio City. BSU, La Trinidad. P. 1.
BERNAL, A.G.AND J.S.LIGAT.1998. Incidence of Virus-Like Diseases Affecting
Chayote In Benguet and Baguio City. BSU Research Journal26. Pp. 59-65
COHEN,S.;DUFFUSs, J.E.; LARSEN,R.C.;LIU,H.Y.; FLOCK, R.A. (1983) Purification,
serology, and vector relationships of squash l eaf curl virus, a whitefly
transmitted geminivirus. Phytopathology 73, 1669-1673.
HORN ET, C. W. ET AL. 1994. Squash Leaf Curl Virus. Education programs of the
Texas AgriLife Extension Service. Texas A & M University, college Station,
Texas 77843.
ILAG, L. L. 1987. Learning the principles of plant pathology.
Philippines;UPLB CA. Program. P.95.
KNOT, J. AND J.R. DEANON. 1 980. Vegetable production in Southeast Asia
UP Press. College of Agriculture, Los Banios, Laguna, Philippines. Pp.
149.
LIGAT, J. S. 1983. Identification of Strawberry virus symptoms by Bioassay.
BS Thesis. MSAC, La Trinidad, Benguet. P. 4.
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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LIGAT, J. S. 2004. Chayote Research and Development. Benguet State
University.P. 1- 52.
LIGAT, J. S. and A. V. G. LUMIQUED. 2000. Plant Pathology. BSU. BS. Thesis. La
Trinidad, Benguet. P.4.
MATHEWS. R. E. F. 1981. Plant Virology. 2nd ed. New York; Academic Press
Inc.Pp.11, 314.
SINGH, R. S. 1978. Plant Diseases. 4th ed. New Delhi; Oxford and IBH Publ.
Co. Pp. 450, 453.
VELASCO, R. B. 1994. Benchmark survey on Chayote production and marketing
practices in La Trinidad. Unpublished Thesis. BSU, La Trinidad, Benguet P. 7.
WALKER,J.C. 1969. Plant Pathology.3rd Edition. New York. Mc Grawhill Book Co. Inc.
Pp.568, 570, 986.
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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APPENDICES
Appendix Table 1. Severity of squash leaf curl virus on the greenhouse 6 days after
Inoculation
REPLICATION
SOURCE OF
INOCULUM I II III IV TOTAL MEAN
LA TRINIDAD 62.67 66.66 77.33 68 274.66 68.66a
TUBLAY 69.33 73.34 46.67 33.33 222.67 55.67a
ATOK 90.67 88 42.67 60 281.34 70.34a
ANALYSIS OF VARIANCE TABLE
SOURCE DEGREE SUM OF MEAN
OF OF SQUARES SUM OF COMPUTED TABULATED F
VARIANCE FREEDOM SQUARES F .05 .01
Replication 4
Treatment 2 515.812615 257.9063075 0.83 ns 3.98 7.20
Error 9 2792.113475 310.2348306
TOTAL 11 3307.92609
NS= Not significant Coefficient of Variation=27.14%
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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Appendix Table 2. Severity of squash leaf curl virus on the greenhouse (systemic
Infection)
REPLICATION
SOURCE OF
INOCULUM I II III IV TOTAL MEAN
LA TRINIDAD 53.33 53.33 65.33 62.67 234.66 58.66a
TUBLAY 64 66.66 72 70.67 273.33 68.33a
ATOK 35.33 10.67 56 64 156 39b
ANALYSIS OF VARIANCE TABLE
SOURCE DEGREE SUM OF MEAN
OF OF SQUARES SUM OF COMPUTED TABULATED F
VARIANCE FREEDOM SQUARES F .05 .01
Replication 4
Treatment 2 1787.42445 893.712205 3.90ns 3.98 7.20
Error 9 2061.326775 229.0363083
TOTAL 11 3848.75122
NS= Not significant Coefficient of Variation=27.35%
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
26
Appendix Table 3. Severity of squash leaf curl virus (Field Survey)
REPLICATION
SOURCE OF
INOCULUM I II III IV TOTAL MEAN
LA TRINIDAD 55 57 51 54 217 54.25a
TUBLAY 47 46 54 41 188 47b
ATOK 44 47 49 49 189 47.25a
ANALYSIS OF VARIANCE TABLE
SOURCE DEGREE SUM OF MEAN
OF OF SQUARES SUM OF COMPUTED TABULATED F
VARIANCE FREEDOM SQUARES F .05 .01
Replication 4
Treatment 2 135.5 67.71 3.94ns 3.98 7.20
Error 9 102.83 17.14
TOTAL 11 352836
NS= Not significant Coefficient of Variation= 8.36%
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
27
Appendix Table 4. Incidence of squash leaf curl virus (Field Survey)
REPLICATION
SOURCE OF
INOCULUM I II III IV TOTAL MEAN
LA TRINIDAD 55 65 40 40 200 50a
TUBLAY 45 45 40 55 185 46.25a
ATOK 50 45 50 50 195 48.75a
ANALYSIS OF VARIANCE TABLE
SOURCE DEGREE SUM OF MEAN
OF OF SQUARES SUM OF COMPUTED TABULATED F
VARIANCE FREEDOM SQUARES F .05 .01
Replication 4
Treatment 2 29.2 14.6 0.19ns 3.98 7.20
Error 9 470.8 78.47
TOTAL 11 336400
NS= Not significant Coefficient of Variation= 18.33%
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
PATRICIO, JOEYLITO G. APRIL 2011. Incidence and Severity of Squash Leaf Curl
Virus Infection on Chayote in La Trinidad, Tublay and Atok, Benguet. Benguet State University,
La Trinidad, Benguet.
Adviser: Julio S. Ligat, Ph.D.
ABSTRACT
This study was conducted to assess the incidence and severity of Squash Leaf Curl Virus
on Chayote in La Trinidad, Tublay and Atok, Benguet.
Results in the greenhouse experiment revealed that the municipality of Tublay had the
lowest Squash Leaf Curl Virus local lesion and systemic severity. The Municipality of Atok and
La Trinidad had the highest disease severity.
In the field survey, the chayote plantation in Tublay, Benguet had the lowest Squash Leaf
Curl Virus disease severity and disease incidence. The Municipalities of Atok and La Trinidad,
Benguet had the highest of disease severity and disease incidence of Squash Leaf Curl Virus.
TABLES OF CONTENTS
Page
Bibliography...……………………………...................................................... i
Abstract ……………………………………………………………………….. i
Table of Contents ………………………………………………………….... ii
INTRODUCTION……………………………………………………………. 1
REVIEW OF LITERATURE………………………........................................ 4
About the Disease……………………………………………………… 4
Virus Symptoms………………………………...................................... 4
Transmission of Viruses………………………........................................ 6
MATERIALS AND METHODS……………………………………………… 8
Survey of Squash Leaf Curl on
Chayote……………………………….................................................... 8
Mechanical Transmission of
Squash Leaf Curl Virus ………………………………………………… 8
Data Gathered…………………………………...................................... 12
RESULTS AND DISCUSSION……………......................................................... 14
Visual Symptoms of Squash
Leaf Curl Virus on Chayote………………………………………………. 14
Severity of Squash Leaf Curl
Virus of Chayote in the BSU
Greenhouse…………….............................................................................. 15
Field Survey on the Severity
and Incidence of Squash Leaf
Curl Virus……………………...................................................................... 18
SUMMARY, CONCLUSIONS AND RECOMMENDATIONS……................. 20
Summary……………………………………………................................... 20
Conclusions……………………………………………………………….. 20
Recommendations…………………………………………........................ 20
LITERATURE CITED…………………………………………………………… 22
APPENDICES……………………………………………………………………. 24
1
INTRODUCTION
Chayote (Sechium edule) is a perennial, training vine bearing edible fruits which
belong to family Cucurbitaceae. Knot and Deanon (1980) stated that the chayote is a
nature of Mexico, Central America and the West Indies.
Chayote and other crops belonging to the Cucurbit family are given on overhead
trellis (Knot and Deanon, 1980). In addition, side trellis is used to withstand strong wind
in wind prone areas. This practices combined with judicious pruning will enhance more
yield for the crop. If they reach the desirable size, they are harvested manually (Velasco,
1994).
The symptoms exhibited by a virus infected plant may be due to other factors
such as mineral deficiency, insects, nematodes, fungi and other environmental factors.
But, oe of the many ways to determine virus infected plant is the shortening of internodes
(Bawden, 1964) and curing of leaves.
Virus is one of the pathogen that is difficult to control because it is highly
dependent on the disseminating agents such as insects. In addition, viruses could also be
transmitted mechanically by the use of contaminated garden tools of manual handling of
plant part by man.
The squash leaf curl virus affects most cucurbits, with cucumber showing the
least symptoms. Leaves are cupped upward, new growth bends upward, and mid-vein
portions of leaves are severely mottled. Flowers and fruit are small and abnormally
developed. Control measures focus on lowering the potential virus inoculums in the area.
These measures include that weeds around the fields do not harbor whiteflies and destroy
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
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2
infected crops as soon as practical after harvest. Controlling the whiteflies directly has
not proved successful (Horn et al., 2004)
Squash leaf curl is transmitted persistently by both biotypes of the sweetpotato
whitefly, Bemesia tabaci. It has been a problem in Arizona in fall watermelons in the
central part of the state. Infection of young plants causes severe curling, and small leaves
that are mottled and yellowing. Often an entire field may be affected, but young plants
have been seen to grow out of the disease. It occurs primarily in squash and watermelon.
No resistant varieties are known, but a host free period with sanitation and weed control
may reduce subsequent infections.
Like in most municipalities of Benguet, vegetable farming is one of the sources of
livelihood among the municipality population of La Trinidad, Tublay and Atok. Chayote
is raised throughout the year and is preferred by farmers of Benguet because it is easy to
sell at local and city markets.
At present, one of the problems faced by farmers in growing chayote is the
incidence of disease exhibiting the upward cupping of leaves bending of new growth
upward, and severe mottling of the mid-vein portions of leaves. No management
strategies are being employed for these disease infections. Thus, information on the
disease characteristics like incidence and severity would be of great help to the chayote
farmers of La Trinidad, Tublay and Atok, Benguet.
The study aims to assess the incidence and severity of squash leaf curl virus
infection on chayote La Trinidad, Tublay and Atok, Benguet.
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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The survey was conducted in selected existing chayote plantation at La Trinidad, Tublay
and Atok, Benguet. The mechanical transmission activity was conducted in the Plant
Pathology Greenhouse, College of Agriculture, Benguet State University, La Trinidad,
Benguet.
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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REVIEW OF LITERATURE
About the disease
Squash leaf curl virus (SLCV) was detected for the first time in Jordan using
degenerated oligonucleotide primers. Two isolates of the virus, SLCV-E and SLCV-R,
were detected using specific oligonucleotide primers in symptomatic Cucurbita pepo.
SLCV was also found to occur naturally in Malva parviflora, which showed severe leaf
curling, yellowing and stunting of the whole plants. The full-length genomes of Squash
leaf curl virus-Malva (SLCV-Malva) isolate were amplified using the bacteriophage Φ
DNA polymerase enzyme. Nucleotide sequence analysis showed that SLCV-Malva
shared high nucleotide identity (98% and 97%) with SLCV-EG and SLCV-E from Egypt
and USA, respectively. A survey using dot-blot hybridization indicated that squash leaf
curl disease occurred in all surveyed areas. The highest disease incidence (95%) was
recorded in Dir Alla area, whereas disease incidence did not exceed 69% in squash
samples collected from North Ghor (Al_Muza, 2007).
Virus Symptoms
Diener (1967) as stated by Singh (1978) cited that infected plants show
histopathology changes as hyperthrophy, hyperplasia, and necrosis. The physiology of
the plant is affected as shown in the decreased photosynthetic activity, increased activity
of phenophenoloxides and accumulation of oxidized polyphenol derivatives and
increased activity of growth regulating substances.
Janick (1972) as cited by Angadol (1983) grouped the virus diseased into two;
the yellow viruses and mosaic viruses. Symptom of the yellow viruses include yellowing,
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
5
leaf curling, dwarfing, excessive branching, shortening of the mosaic viruses includes a
mosaic appearance and mottling which is due to chlorosis in small areas of the plant
following the death of the tissues.
Smith (1972) as cited Angadol (1983) mentioned that in the field, infected plants
are readily recognized by their reduced size and different growth habits and by marked
changed in leaf color and shape, flower buds are killed and reduced yields are obtained
when infection occurs before motivation of plants or fruits.
Tarr (1972) as cited by Angadol (1983) stated that symptoms of virus diseases in
plants are varied, often severe and sometimes so slight that it cannot be noticed
immediately except on close examination. Symptoms may disappear under certain
environmental conditions such as high temperature, or following the application of
certain fertilizers. Some plants may show no outward symptoms even if they contain the
virus.
Singh (1978) also mentioned that plant viruses are infections and sometimes
highly contagious. However, Mathews (1981) mentioned that virus infections do not
necessarily caused disease at all times in all parts of an infected plants. There are at least
five (5) situations in which disease may be absent. They are, infection with a very mild
strain of the virus; a tolerant host, nonsterile “recovery” from disease symptoms in newly
formed leaves; leaves that escape infection because of their age and positioned in the
plant; and dark green areas in a mosaic pattern.
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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Transmission of Viruses
One of the cardival characters of a virus is the fact that it has infections. However,
it was recognized early, that viruses differ widely in the means and in the ease with which
they may be transmitted. Some can be transmitted easily while others are difficult to
transmit by artificial means. Some viruses have been transmitted by only one method
while others are has been transmitted by two or more methods. This was brought about
by the coincidence that the two viruses studied first, peach yellow and tobacco mosaic
represents extremes. The common tobacco mosaic virus is transmitted readily by simple
mechanical means, while peach yellow virus is transmitted by us of buds and graft.
As cited by Ilag (1987), viruses are transmitted by mechanical means, by
nematodes, by certain soil-borne fungi, by mites, through infected seeds and through
infective vegetative planting materials.
Moreover, Singh (1978) further stated other means through which virus can be
transmitted by vegetatively reproductive parts, transmission by grafting and budding,
transmission of viruses by pollen, transmission by seed, transmission of viruses through
weeds and flowering plants parasites, transmission of viruses through insects and
transmission by contact of diseased plant and healthy plants.
The same author further stated that the insects can transmit only one specific virus
to only one species of the host plant while other transmit as single virus to more than one
species of the host.
Walker (1969) reported that viruses which are readily more transmitted
mechanically are aphids and those which do not yield to such transfer are leaf hopper-
borne. Furthermore, there are differences among vectors and their relation to the virus
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
7
they transmit. Some viruses transmitted by aphids and whiteflies are carried in such a
way that the vectors remain viruliferous for a period of only a few minutes to a few
hours. These virus as cited by Ligat (1983) are called stylet-borne viruses. The same
species of aphids and whiteflies may transmit the virus after several hours after it is
possible that the virus infected by the insects is later transmitted through the body into the
saliva, by which channel it eventually reaches the next host plant.
Ilag (1987) also reported that viruses are transmitted mechanically. Bawden
(1964) stated that the many reported failures to infect plants in mechanical transmission
by inoculation with extract from infected ones, reflect the intrinsic behavior of the
infective virus is doubtful. He further stated that the failures most probably occurred
because the properties of either the plant yielding the extract or the one inoculated
prevented infection. Moreover, virus inoculum containing adequate concentration of
virus, transmission and deposition of virus through abrasive (such as carborandum)
causing injuries on the plant, and establishment of infection by placing the polycestronic
viral genome first, are the factors essentially for mechanical transmission.
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
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MATERIALS AND METHODS
Survey of Squash Leaf Curl Virus on Chayote
A survey and documentation of the incidence and severity of Squash Leaf Curl
Virus infection on chayote was done at the selected municipality of La Trinidad, Tublay
and Atok, Benguet. From the selected sites samples of infected leaves with SLRV, were
gathered and was used for inoculation at the greenhouse of BSU.
Mechanical Transmission of Squash Leaf Curl Virus On Chayote
1. Source of samples. Leaves suspected of being infected with Squash Leaf Curl
Virus were collected in existing chayote farms in the municipality of La Trinidad, Tublay
and Atok, Benguet.
2. Preparation and inoculation of test plants. Previously germinated seedlings of
Vigna umbellate were used as indicator plant in the study. This plant was used because; it
showed prominent manifestation of Squash Leaf Curl Virus symptoms (Cohen et al.
1983). The seedlings were transplanted in black plastic bags. The seedlings at four to six
leaf stages were used as test plants.
3. Mechanical Transmission experiment. Prior to bioassay, suspected Squash Leaf
Curl Virus infected chayote leaf samples were weighed to determine the amount of
phosphate buffer that was added. The sap was extracted with the use of mortar and pestle.
Before inoculation, the upper left surface of test plants was dusted with carborundum
powder # 320. Sap inoculation was done by dipping the forefinger into the pestle
containing the mixture of sap and buffer and then rubbing it gently on the carborundum-
dusted leaves. After inoculation, the inoculated leaf surfaces were washed with distilled
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
9
water to remove carborundum dust. Each test plants were labeled properly. Inoculated
test plants were incubated inside the greenhouse and then observed for reactions daily for
three weeks. Photographs of the plants showing symptoms were taken.
Figure 1. Map of the surveyed sitios in La Trinidad, Benguet
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
10
Figure 2. Map of the surveyed sitios in Atok, Benguet
Figure 3. Map of surveyed sitios in Tublay, BengueT
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
11
Figure 4. Mechanical transmission activities in the greenhouse
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
12
Data Gathered
1. Severity of Squash Leaf Curl Virus on Chayote
A. Green House
The number of necrotic spots on the inoculated Vigna umbellata (as test plants),
were assessed using the arbitrary rating scale below (Ligat and Lumiqued, 2000).
Scale Description
0
No infection
1
Mild infection, 1-10 necrotic spots in
inoculated leaf, local infection.
3
Moderate infection, 11-25 necrotic spots in
inoculated and uninoculated leaf, systemic
infection
5
Severe infection, 26-50 necrotic spots in
inoculated and uninoculated leaf, systemic
infection.
Disease severity will be expressed
DS = n (0) + n (1) + n (3) + n (5) x 100
N x5
Where:
n- Number of necrotic spots classified by scale.
N- Total number of sample plants
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
13
B. Field Condition
Twenty plants were selected per surveyed area and rated for disease severity. The
severity was assessed using the arbitrary rating scale below (Ligat and Lumiqued, 2000).
Scale Description
0
No infection
1
Mild infection, 1-10 infected leaves per
plant.
2
Moderate infection, 11-25 infected leaves
per plant.
5
Severe infection, 26-50 infected leaves per
plant.
Disease severity will be expressed as:
DS = n (0) + n (1) + n (3) + n (5) x 100
N x5
Where:
n = number of infected leaves per plant classified by scale.
N = total number of plants
3. Incidence of Squash Leaf Curl Virus on chayote. The presence or absences of
Squash Leaf Curl Virus - infected chayote plants were recorded. The datum was
determined by dividing the number of infected plants over the total number of sample
plants multiplied by 100.
4. Location map showing the different sites.
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
14
RESULTS AND DISCUSSION
Visual Symptoms Of Squash
Leaf Curl Virus on Chayote
Infected leaves are frequently puckered and mottled yellow or light green leaf
symptoms are more evident on younger leaves (Figure 5). Plants can be stunted (Figure
6) especially when the infection occurs early in the development. Although infected fruit
can be reduced in size and show variation in colors, the most obvious symptoms is
distorted or lumpy appearance (Figure 7).
Figure 5. Leaf stunting on Chayote caused by SQLV
Figure 6. Stunting of young Chayote caused by SQLV
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
15
Figure 7. SQLV symptoms on Chayote
Severity of Squash Leaf Curl Virus
on Chayote in the Greenhouse
Squash Leaf Curl Virus infected chayote leaf samples from the three
municipalities were transmitted mechanical to Vigna umbellate which served as indicator
plant in the greenhouse. Six days after inoculation, local lesions were recorded in
infected samples from Tublay, which had the lowest disease infection (Table 1). The
Municipality of Atok and La Trinidad had the highest disease severity of 70.34 and 68.66
percent.
Twelve days after inoculation (Figure 10), the disease infection became systemic
where infection exhibiting necrotic lesions after six days of inoculation. This was
observed in the samples from Tublay municipality which had the lowest Squash Leaf
Curl Virus severity and in Atok and La Trinidad which registered the highest of 68.33
and 58.66 percent.
It could be noted from the results that there was a virulent strain of Squash Leaf
Curl virus in Tublay, Benguet. Another implication could be the phenomenon of Squash
Leaf Curl Virus latent infection in Atok and La Trinidad, Benguet.
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
16
The Chayote plantation in Ambassador, Tublay, Benguet were intercropped with
a tree (alnus), trumpet flower and flower of the night or “Dama de Noche” which are
non-hosts of Squash Leaf Curl Virus.
The presence of alnus trees may have resulted to the low the Squash Leaf Curl
Virus in Tublay which conforms with the findings of Ligat (2004) that alnus trees
enhanced growth vigor of chayote and develop resistance against Squash Leaf Curl due
to the nitrogen-fixing capacity of alnus species, saturated by light of one-tenth the higher
intensities which increases photosynthetic rate it also releases low molecular weight
substances from decayed debris which taken up by chayote resulting to an increased
metabolism and influence development of resistance against the virus disease.
Table 1. Severity of squash leaf curl virus in the BSU (Greenhouse Experiment)
SOURCE OF INOCULUM LOCAL LESION SYSTEMIC INFECTION
La Trinidad 68.66 58.66a
Tublay 57.67 39.00b
Atok 70.34 68.33a
Coefficient of Variation 27.14% 27.35%
Means followed by common letters are not significantly different at 5% level DMRT
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
17
a b c
Figure 8. Samples of Vigna umbellate as indicator plant (Internet) (a. uninoculated
b. necrotic lesion, c. systemic infection)
a
b
Figure 9. Samples of Vigna umbellate as indicator plant (Present study) a. uninoculated
b. inoculated
Figure 10. Systemic infection of SQLV after 12 days of inoculation
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
18
Field Survey on the Severity and Incidence
of Squash Leaf Curl Virus
The Chayote plantation in Tublay, Benguet had the lowest Squash Leaf Curl
severity which had comparable results with the chayote plantation in Atok, Benguet
(Table 2, Figure 11 and 12). The highest disease severity was observed in La Trinidad,
Benguet (Figure, 13).
Tublay, Benguet (Figure 12) had the lowest incidence of Squash Leaf Curl Virus
and La Trinidad municipality (Figure 13) had the highest disease incidence.
The Chayote plantation in La Trinidad, Benguet had abundant wild sunflowers
around the vicinity of the farm which provided a haven for whiteflies which is a vector of
the virus. The surrounding was also covered with lime stones which emit heat and
enhance the dryness of the plantation making conditions favorable for whiteflies
population increase.
Table 2. Severity and incidence of squash leaf curl virus in the field
SOURCE OF INOCULUM SEVERITY INCIDENCE
La Trinidad 54.25 50a
Tublay 47 46.25a
Atok 47.27 48.75a
Coefficient of Variation 8.36% 18.33%
Means followed by common letters are not significantly different at 5% DMRT
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
19
Figure 11. Chayote plantation in Atok, Benguet which had the lowest systemic
Symptom of SQLV
Figure 12. Chayote plantation in Tublay, Benguet which had the lowest local lesion
Smptom of Squash Leaf Curl Virus severity
Figure 13. Chayote plantation in La Trinidad, Benguet which had the highest
Symptom of Squash Virus severity and incidence
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
20
SUMMARY, CONCLUSIONS AND RECOMMENDATIONS
Summary
This study was conducted to assess the severity and incidence of Squash Leaf
Curl Virus on chayote in La Trinidad, Tublay and Atok from August to March 2011.
In the greenhouse study it was noted that six days after inoculation, the
representative test plants of Tublay had the lowest number of necrotic spots while the
more necrotic spots were observed in plants inoculated with samples from Atok and La
Trinidad. Twelve days after inoculation, systemic infection was noted where samples
from Tublay had the lowest infection and in Atok and La Trinidad with the highest
infection.
In the field survey, the chayote farm in Tublay had the lowest severity and
incidence of SQLV and the highest was observed in La Trinidad. Incidence of the virus in
La Trinidad and Atok was 100%.
Conclusions
Based on the results, the incidence and severity of SQLV infection on chayote in
La Trinidad, Tublay and Atok, Benguet ranged from 47% to 100%. SQLV is transmitted
by whiteflies but can also be mechanically transmit.
Recommendations
It is recommended that farmers should take precautions in obtaining chayote
planting materials from La Trinidad, Tublay and Atok as there were high severity and
incidence of Squash Leaf Curl Virus. Further, farmers should initiate proper care and
control measures not to spread the virus as it could be mechanically transmitted. Field
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
21
sanitation should be observed by farmers in order to prevent the proliferation of
alternative hosts and white flies as vector of the disease.
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
22
LITERATURE CITED
AGRIOS, G. N. 1997. Plant Pathology. 4th ed. New York: Academy Press. Pp.
479-490.
AL MUZA, A. 2007. Detection and Molecular Characteristics of Squash Leaf Curl Virus
(SQLV) in Jordan, Departmen t of Plant Protection, Faculty of
Agriculture, University of Jordan, Amman, Jordan.
ANGADOL, P. P. 1983. A survey on the incidence and identification of virus symptoms
on the Important flower in Benguet . BS Thesis. BSU, La Trinidad,
Benguet. P.1.
BATNAG, A.G. AND J.S. LIGAT. 1996. Symptomatology and sap transmission of virus
like diseases of chayote in Benguet and Baguio City, BS Thesis. Benguet
State University, La Trinidad, Benguet.
BAWDEN. F. C. 1964. Plant virus disease. 4th New York; Ronald Press Co.
P. 97.
BOGSULEN, R. A. 1996. Ocular survey on the incidence of virus-like disease affecting
Chayote in Benguet and Baguio City. BSU, La Trinidad. P. 1.
BERNAL, A.G.AND J.S.LIGAT.1998. Incidence of Virus-Like Diseases Affecting
Chayote In Benguet and Baguio City. BSU Research Journal26. Pp. 59-65
COHEN,S.;DUFFUSs, J.E.; LARSEN,R.C.;LIU,H.Y.; FLOCK, R.A. (1983) Purification,
serology, and vector relationships of squash l eaf curl virus, a whitefly
transmitted geminivirus. Phytopathology 73, 1669-1673.
HORN ET, C. W. ET AL. 1994. Squash Leaf Curl Virus. Education programs of the
Texas AgriLife Extension Service. Texas A & M University, college Station,
Texas 77843.
ILAG, L. L. 1987. Learning the principles of plant pathology.
Philippines;UPLB CA. Program. P.95.
KNOT, J. AND J.R. DEANON. 1 980. Vegetable production in Southeast Asia
UP Press. College of Agriculture, Los Banios, Laguna, Philippines. Pp.
149.
LIGAT, J. S. 1983. Identification of Strawberry virus symptoms by Bioassay.
BS Thesis. MSAC, La Trinidad, Benguet. P. 4.
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
23
LIGAT, J. S. 2004. Chayote Research and Development. Benguet State
University.P. 1- 52.
LIGAT, J. S. and A. V. G. LUMIQUED. 2000. Plant Pathology. BSU. BS. Thesis. La
Trinidad, Benguet. P.4.
MATHEWS. R. E. F. 1981. Plant Virology. 2nd ed. New York; Academic Press
Inc.Pp.11, 314.
SINGH, R. S. 1978. Plant Diseases. 4th ed. New Delhi; Oxford and IBH Publ.
Co. Pp. 450, 453.
VELASCO, R. B. 1994. Benchmark survey on Chayote production and marketing
practices in La Trinidad. Unpublished Thesis. BSU, La Trinidad, Benguet P. 7.
WALKER,J.C. 1969. Plant Pathology.3rd Edition. New York. Mc Grawhill Book Co. Inc.
Pp.568, 570, 986.
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
24
APPENDICES
Appendix Table 1. Severity of squash leaf curl virus on the greenhouse 6 days after
Inoculation
REPLICATION
SOURCE OF
INOCULUM I II III IV TOTAL MEAN
LA TRINIDAD 62.67 66.66 77.33 68 274.66 68.66a
TUBLAY 69.33 73.34 46.67 33.33 222.67 55.67a
ATOK 90.67 88 42.67 60 281.34 70.34a
ANALYSIS OF VARIANCE TABLE
SOURCE DEGREE SUM OF MEAN
OF OF SQUARES SUM OF COMPUTED TABULATED F
VARIANCE FREEDOM SQUARES F .05 .01
Replication 4
Treatment 2 515.812615 257.9063075 0.83 ns 3.98 7.20
Error 9 2792.113475 310.2348306
TOTAL 11 3307.92609
NS= Not significant Coefficient of Variation=27.14%
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
25
Appendix Table 2. Severity of squash leaf curl virus on the greenhouse (systemic
Infection)
REPLICATION
SOURCE OF
INOCULUM I II III IV TOTAL MEAN
LA TRINIDAD 53.33 53.33 65.33 62.67 234.66 58.66a
TUBLAY 64 66.66 72 70.67 273.33 68.33a
ATOK 35.33 10.67 56 64 156 39b
ANALYSIS OF VARIANCE TABLE
SOURCE DEGREE SUM OF MEAN
OF OF SQUARES SUM OF COMPUTED TABULATED F
VARIANCE FREEDOM SQUARES F .05 .01
Replication 4
Treatment 2 1787.42445 893.712205 3.90ns 3.98 7.20
Error 9 2061.326775 229.0363083
TOTAL 11 3848.75122
NS= Not significant Coefficient of Variation=27.35%
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
26
Appendix Table 3. Severity of squash leaf curl virus (Field Survey)
REPLICATION
SOURCE OF
INOCULUM I II III IV TOTAL MEAN
LA TRINIDAD 55 57 51 54 217 54.25a
TUBLAY 47 46 54 41 188 47b
ATOK 44 47 49 49 189 47.25a
ANALYSIS OF VARIANCE TABLE
SOURCE DEGREE SUM OF MEAN
OF OF SQUARES SUM OF COMPUTED TABULATED F
VARIANCE FREEDOM SQUARES F .05 .01
Replication 4
Treatment 2 135.5 67.71 3.94ns 3.98 7.20
Error 9 102.83 17.14
TOTAL 11 352836
NS= Not significant Coefficient of Variation= 8.36%
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
27
Appendix Table 4. Incidence of squash leaf curl virus (Field Survey)
REPLICATION
SOURCE OF
INOCULUM I II III IV TOTAL MEAN
LA TRINIDAD 55 65 40 40 200 50a
TUBLAY 45 45 40 55 185 46.25a
ATOK 50 45 50 50 195 48.75a
ANALYSIS OF VARIANCE TABLE
SOURCE DEGREE SUM OF MEAN
OF OF SQUARES SUM OF COMPUTED TABULATED F
VARIANCE FREEDOM SQUARES F .05 .01
Replication 4
Treatment 2 29.2 14.6 0.19ns 3.98 7.20
Error 9 470.8 78.47
TOTAL 11 336400
NS= Not significant Coefficient of Variation= 18.33%
Incidence and Severity of Squash Leaf Curl Virus Infection on Chayote in La Trinidad,
Tublay and Atok, Benguet . PATRICIO, JOEYLITO G. APRIL 2011
Document Outline
- Incidence and Severity of Squash Leaf CurlVirus Infection on Chayote in La Trinidad, Tublay and Atok, Benguet
- BIBLIOGRAPHY
- TABLES OF CONTENTS
- INTRODUCTION
- REVIEW OF LITERATURE
- MATERIALS AND METHODS
- RESULTS AND DISCUSSION
- SUMMARY, CONCLUSIONS AND RECOMMENDATIONS
- LITERATURE CITED
- APPENDICES