Plant Virus Diseases in Nepal: Current
Status and Future Strategies
Dr. RD. Timila , S. Joshi and Dr. BN. Mahto
Plant Pathology Division,
Nepal Agriculture Research Institute,
Nepal Agricultural Research Council
Khumaltar
Contents
• Background Information
• Economic Significance
• Prevalent plant virus diseases in Nepal and
their distribution
• Current status of major virus diseases in
vegetable crops
• Seed-borne virus diseases of vegetable
crops
• Diagnostic Methodologies
• Constraints
• Future Strategies and Needs
Introduction
• Cultivation of various vegetables is one of the
most potential income generating sources for
the livelihood of the majority of the farmers
• High value crops
• Vegetable cultivation:
Area under = 245037 h
Production = 3298816 mt
Productivity= 13.46 mt/h
(Source: Vegetable Development Directorate, Annual
Report, 2011/12)
• Diseases are one of the major constraints of
successful cultivation
• Epidemic of some of the diseases are
causing havoc with negative impact on the
economy of the farmers
• In recent years, viral disease problem
appearing as the most important diseases for
some of the major vegetable crops.
• It induces broad range of symptoms
affecting growth, yield and quality of
the produce
• Its incidence and severity is increasing
• New virus
emerging
like
diseases
are
also
• Research and studies on plant viruses
are limited in Nepal
Economic Significance
. Crop loss estimated 15-20% due to disease
alone (Rajbhandary and Shrestha, 1992)
• In recent years, ‘virus diseases‘ caused
significant Yield losses
• Posed a threat for production and productivity
of important crop plants especially vegetables
• Deteriorate both quality and quantity of
produce and ultimately reduces market price
• Its economic importance has been realized
since past many years.
• Crop or yield losses incurred due to specific
virus in specific crop in Nepal is not yet
studied.
• However, some seed borne viruses could cause
yield loss (Shrestha and Albrechtsen,1992)
depending on type of virus and the crop.
– PSbMV in pea: up to 36%
– SBMV in cowpea: up to 59%
– CAMV in cowpea: up to 87%
Prevalent plant virus diseases in Nepal and their
distribution
Cereals and Legumes:
Crop
Virus disease
Distribution/inc.
Rice
Rice Tungro Virus, Rice dwarf Virus
Eastern & Central
terai, Kath
Maize
Maize Leaf Fleck Mosaic Virus
Rampur
Wheat
Barley Yellow Dwarf Virus
Bhairahawa (Terai)
Soybean
Soybean Mosaic Virus, Tobacco
Ring Spot Virus, Mungbean Yellow
Mosaic Virus
Terai and mid-hills
Cowpea
Cowpea Aphid-borne Mosaic Virus,
Cowpea Mosaic Virus
Chitwan,
Pea and
Broad
bean
Pea Seed- borne Mosaic Virus
(in seed samples)
Prevalent plant virus diseases in Nepal ………(contd.)
Cereals and Legumes (contd.):
Crop
Lentil
Virus disease
Pea Seed- borne Mosaic Virus
Distribution
Mid-hills (In seed)
Pigeon pea Sterility Mosaic Virus, Yellow Mosaic Terai and inner
Virus
terai, (15-50% inc.)
Blackgram
Bean Common Mosaic Virus
(in seed)
Mungbean
Mungbean Yellow Mosaic Virus
Terai
Groundnut Tomato Spotted Wilt Virus (Bud
necrosis)
Terai
Prevalent plant virus diseases in Nepal …….(Contd)
Vegetables crops:
Crop
Virus disease
Distribution
Tomato
Tomato Mosaic Virus, Tomato
Terai, inner terai
Leaf Curl Virus, Cucumber Mosaic and mid-hills
Virus
Pepper (Chili
and
capsicum)
Tomato Leaf Curl Virus, Chili
Veinal Mottle Virus, Cucumber
Mosaic Virus
Terai, inner terai
and mid-hills
Cucumber
and Zucchini
squash
Cucumber Mosaic Virus, Zucchini
Yellow Mosaic Virus, Watermelon
Mosaic Virus 1 and 2, Squash
Mosaic virus, Cucumber Green
Mottle Mosaic Virus
Mid-hills, terai
Prevalent plant virus diseases in Nepal …….(Contd)
Vegetables crops:
Crop
Virus disease
Distribution
Broad leaf
mustard, Turnip,
Radish
Turnip Mosaic Virus
Mid-hills
Okra
Yellow Vein Mosaic Virus
Terai, inner terai
and mid-hills
Bean
Bean Common Mosaic Virus, Mid-hills,
Y. Long bean
Southern Bean Mosaic Virus
Mid-hill and Terai
Prevalent Plant virus diseases in Nepal…. (contd.)
Fruits and cash crops:
Crop
Virus disease
Distribution
Potato
Potato Leaf Roll Virus*, Potato
Virus X, Potato Virus Y*, Potato
Virus A, Potato Virus S, Potato
Virus M
*Terai, Mid-hills and
high hills
Large
cardamom
Large Cardamom Chirkey Virus
Ilam, Panchthar,
Chirkey), Cardamom Bushy Dwarf Taplejung,
Virus (Foorkey)
Citrus
Citrus Tristeza Virus
Mid-hills: Kaski,
Dhankuta and
Dailekh
Papaya
Papaya Ring Spot Virus
Terai, Inner terai
and foot-hills
Tobacco
Tobacco Mosaic Virus, Tobacco
Leaf Curl, Cucumber Mosaic
Virus (Strain)
Terai and inner terai
Current status of major virus diseases in
vegetable crops:
Tomato
 TLCV
– First reported in 1994
(Timila and Joshi, 1994)
after diagnosis using
cDNA hybridization in
collaboration with Dr.
Maxwell
(Univ.
of
Wisconsin) and AVRDC.
– The virus is distributed
in terai, inner terai,
valleys and foothills.
• Incidence ranged from
40-70% (Joshi et al.1997) .
• Yield loss estimation in
tomato was 50% (Joshi
and Shrestha, 1999), 40%
in Western hills (Ghimire
et al., 2000).
• In recent years also, the
disease is severe in
western terai.
 Tomato
mosaic
virus
(ToMV): Prevalent in tomato
growing areas causing poor
plant growth and also
appeared in combination
with other viruses.
 Cucumber mosaic virus (CMV):
Widely distributed in tomato growing areas
of the mid-hills. Observed to be major.
Severely affected in some of the fields.
CMV in Tomato
CMV with other virus comlex
Virus ?
Pepper:
Virus complex varied from 3090%. (joshi and Shrestha, 2001,
AVRDC)
 TLCV: Distributed in terai,
inner terai, valleys and foothills.
Incidence ranged from 20-80%
(Chilli) (Joshi et al.1997) .
 Chilli veinal mottle virus
(CVMV): Higher Incidence and
severity in pepper has been
observed at Kathmandu valley
(mid hills). Virus infected plants
were more than 80% recorded
(Shrestha and Albrechtsen,
1992). In recent years also, the
disease status remaining the
same.
 Cucumber mosaic Virus
(CMV):
Widely distributed in terai,
inner terai and midhills.
The incidence ranged from
50-80% (SAVERNET II,
midterm
report.
1999).
Presently also the disease
is problematic.
Cucurbit:
 CMV in cucumber , distributed
throughout cucumber cultivated
areas of mid-hills in severe form
as revealed by sample received
at PPD, Khumaltar and as
observed in the farmers’ fields,
causing considerable losses
(PPD, 2003-2013).
 Complex infection of CMV,
ZYMV, SqMV, WMV 1 and 2, and
CGMMV in zucchini squash.
Infection in some of the fields,
up to 100% incidence at Kath.
valley causing total crop failure
(PPD, 2006).
Various virus (Complex) disease symptoms in
Zucchini squash
Bottle gourd
Broad leaf mustard:
Turnip mosaic virus
(TuMV):
Observed
mainly in broad leaf
mustard but radish
and
turnip
also
affected.
Widely
distributed in the mid
hills. Incidence up to
100%, causing total
crop failure in some
of the fields.
Beans:
Bean common mosaic
virus (BCMV) has been
observed in Bean fields in
low
incidence.
Its
distribution mainly in the
mid-hills (as observed in
the field visits)
Bean common mosaic
necrosis virus (BCMNV)
recently
reported
from
Kaski and Chitwan in Sweet
bean
with
incidence
ranging
from
60-70%
(Pudasaini et al., 2013).
Okra:
Mainly distributed in
terai, inner terai and
valleys of the mid
hills. up to 70%
incidence observed
(Dahal, 1990). At
present this disease
is
under
high
priority also.
Potato: reported six viruses
 Potato leaf roll virus and
potato virus y: distribution
high in terai and moderate
in midhills. They could
cause yield loss 12-50% and
80% respectively.
 PVX, PVA, PVS and PVM,
their distribution ranged
from 24-27% higher in the
Terai (24, 25, 27, 25%) but
lesser than PLRV and PVY),
Comparatively, PVX and
PVS higher in high hills
also.
(Source, Dhital et al., 2010)
Cardamom:
 Prevalence of Large cardamom
chhirke virus (LCCV) and
Cardamom bushy dwarf virus
(CBDV) have been reported in
the eastern hills with incidence
ranging from 15-20% and 10%
repectively (Srivastav, 2012).
Low
incidence
of
CBDV
observed in our survey.
(These viruses used to be the
issues for cardamom crop, &
losses not estimated yet)
Some important identified seed-borne viruses in
vegetable crops in Nepal
• Tomato mosaic virus (Tomato)
• Cucumber
mosaic
virus
(Tomato,
Pepper,
Cucumber)
• Cucumber green mottle mosaic virus (Zucchini
squash, Cucumber)
• Bean common mosaic virus (Common beans)
• Cowpea aphid borne mosaic virus (Cowpea)
• Southern bean mosaic virus (Yard- long bean)
• Pea seed-borne mosaic virus (Pea)
Field tolerance limit of infected plants for BCMV has been fixed for
seed production of bean crop Foundation seed: 0.1% and for
certified seed: 0.2%
Diagnostic Methodology adopted
• Growing on test
• Indicator host plant test
• Serological test (ELISA): based on the
availability of antiserum
• cDNA hybridization test for TLCV: only
during SAVERNET project period at AVRDC
and Univ. of Wisconsin
Previous Collaboration with International
Intitutions
Training, Technical back-up, Small Lab
equipments and little supplies
• Danish Seed Health Center for Developing
Countries ( Previous DGISP)
• World Vegetable Center (AVRDC)
• ICRISAT
Constraints
• Lack of adequate laboratory facilities for
virological Research
• Lack of controlled condition Green house
facility
• Lack of trained and adequate manpower
• Lack of logistic facilities (Vehicle) for survey
and monitoring
• Inadequate availability of other lab supplies
• Lack of continuous power supply
• Lack of incentive
Future Strategy
• Regular survey and surveillance of virus
diseases in different crop plants through
out Nepal.
• Detection and diagnosis of viruses in major
vegetable crops
• Epidemiological and yield loss studies on
important virus diseases of crop plants
• Seed transmission studies on seed-borne
virus diseases of vegetable crops in
particular
• Host resistance screening
• Alternative
management
Integrated management
tools
for
Felt Needs
For smooth running of Plant virus Research:
• Establishment of molecular laboratory at
plant Pathology Division, NARC
• Establishment of controlled condition green
house.
• Collaboration with International Intitutions
• Strengthening existing green and screen
houses
• Adequate Human resource for virus work
• Capacity
enhancement
:Training
for
personnel in detection, diagnosis, vector
virus relationship and etc
• Exposure visits for scientists/technicians
• Continuous power supply.
Conclusion
• Past and the present virus disease scenario
indicated that the
occurrence of several
viruses
on
cucurbits,
legumes
and
solanaceous vegetables and other crops in
epidemic form in the country.
• Virus suspected diseases observed, yet to be
confirmed
• Emphasis should be given in conducting
research and studies on different aspects of
virus diseases to develop management tools.