Studies on serodiagnosis epidemiology and management of sunflower necrosis viral disease in Northern karnataka

Abstract

Sunflower necrosis is a major virus disease of sunflower caused by Tobacco Streak newlineVirus. It was first reported from Kolar district of Karnataka State during 1997. The roving newlinesurvey for disease incidence in Northern Karnataka was undertaken and disease map was newlinedeveloped, which revealed the presence of disease in all the three seasons.The disease was newlinesevere in Bijapur, Raichur and Koppal districts showing 15-20 per cent incidence. Infected newlineplants showed mosaic, marginal necrosis and malformation of leaves, calyx and earhead, newlineearly infected plants showed partial seed filling. TSV -S had wide host range and its Thermal newlineInactivation Point was 45°C, Dilution End Point 10-4 and Longevity in vitro of 8 h. The newlineepidemiological studies indicated positive correlation of disease with thrips population and newlinealso with maximum temperature. newlineThe virus was purified by extraction in Phosphate buffer, PEG precipitation, density newlinegradient centrifugation and ultra centrifugation. Electron microscopic observations revealed newlineisometric shaped particles in decoration method. Immunizing rabbit with purified TSV -S newlineproduced the antiserum. SDS-P AGE revealed 30 Kda Protein band when stained with newlinecoomassie brillant blue. Direct Antigen Coating Enzyme Linked Immuno Sorbant Assay newlineindicated presence of virus particles in samples of sunflower, cowpea, peas, green gram, newlinetomato, soybean, black gram and red gram but not in seeds of diseased plant. In newlineImmunodiffusion test precipitation line appeared around wells containing diseased samples. newlineRT-PCR yielded 800 bp length coat protein gene. newlineThe disease had a drastic effect on yield parameters of sunflower. Germplasm lines newlineGMU-209, GMU-244, GMU-249, and GMU-259 exhibited some degree of tolerance newlineproperties with less than 10 per cent disease incidence. Crop could be protected from heavy newlineloss due to virus infection by Imidacloprid seed treatment (at 5 g/kg) + spray (at 0.25 ml) at newline30, 45 and 60 days after sowing and sorghum as border crop. newline