MOLECULAR CHARACTERIZATION, EPIDEMIOLOGY AND MANAGEMENT OF TOMATO LEAF CURL VIRUS (ToLCV) IN NORTHERN KARNATAKA
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Date
2007-08-31
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University of Agricultural Sciences GKVK, Banglore
Abstract
Tomato leaf curl virus (ToLCV) disease is one of the most
important viral diseases of tomato and causes substantial losses every
year. Survey results revealed that ToLCV was present in all the fields
visited in Belgaum, Dharwad, Gadag and Haveri districts. The disease
incidence ranged from 4-00 per cent during rabi 2005 and 60-100 per
cent in summer 2006. A few natural weed hosts inz., Parthenium
hysterophorus (Parthenium), Euphorbia geniculata (Bhedi soppu),
Ageratum conyzoides (Oorala gida), Acanthospermum hispidum (Kadale
mullu), Blainvillea rhomboidea (Ervapalha) Cass. and Lachnera pusilla
L. showed positive for ToLCV infection in the PCR detection.
The results of the cloning and nucleotide sequencing of the coat
protein gene revealed that isolates from Belgaum, Dharwad and
Haveri showed 95.10 to 99.60 per cent homology indicating they are
closely related to each other. However, these isolates showed wide
variation of upto 46.50 per cent divergence with some of the isolates of
North Western Indian ToLCV 17 Nasik (AJ 10356) and North Indian
ToLCV 19.Patna (AJ 810358).
The survey, bioassay and RAPD-PCR analysis of whitefly vector
revealed the prevalence of Bemisia tabaci-B-biotype in addition to the
indigenous type in Dharwad region. Tomato planted during August
and November showed slow progress of the disease and less incidence
as there was high humidity and high rainfall, which suppress the
vector activities whereas, maximum incidence was recorded in
February and May planted crop.
In the management of disease the sequential application of
Imidachloprid (0.005%) - Triazophos (0.15%)-Thiamethaxam (0.05%)-
Econeem (0.5%) found effective with low disease incidence and better
yield. The Clerodendron inermis and Glyricidia leaf extract application
also found effective. In the field screening cultivars such as Nandi,
Vybhav, Sankranti, and hybrids Utsav, HY 558, HY 530, NS-719 and
NS-563 showed resistance reaction and the commonly cultivated
Megha showed susceptible reaction.
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