Investigations on Epidemiology and Fungicide Resistance in Plasmopara viticola Berk and Curt Berl and de Toni Downy Mildew and Erysiphe necator Schw Burr Powdery Mildew of Grapes

Abstract

Investigations on epidemiology and fungicide resistance in downy mildew newline[Plasmopara viticola] and powdery mildew [Erysiphe necator] of grapes were carried out at newlineDepartment of Plant Pathology, College of Agriculture, Vijayapur during 2020-22. The newlinesurvey indicated that downy mildew ranged from 18.27 to 65.32 and 5.36 to 70.12% in newlinepowdery mildew during forward/June-July pruning. During back/November-December newlinepruning downy mildew ranged from 0 to 62.12 per cent and powdery mildew was 5.1 to newline60.10 per cent. In northern Karnataka Vijayapur district recorded maximum downy (1.76 newlineand 46.56 %) and powdery mildew (26.16 and 47.46 %) while in southern Karnataka newlinedowny mildew and powdery mildew severity were noticed in Bengaluru rural (59.90 and newline53.30 %) and Chikkaballapur (35.24 and 41.72 %) district during relative pruning periods. newlineThe downy mildew severity was maximum in Dilkush (V. vinifera) variety and lowest in newlineBangalore Blue variety (V. labrusca), whereas powdery mildew severity was maximum for newlineSaritha Krishna and least was recorded for Cabernet Sauvignon. With respect to newlinemorphology of the pathogens; P. viticola formed the tubular, coenocytic hyphae/mycelia (8- newline10 and#956;m dia.) The sporangiophores branched at right angles bearing ellipsoid, hyaline asexual newlinesporangia producing 1-10 biflagellate zoospores. E. necator produced superficial, septate newlinemycelium measuring 5- newlinemeasuring about 29-42×12-20 and#956;m in dimension. Molecular variability confirmed that newlineisolates AGL (Acc. ON183965) of powdery mildew and VJP (Acc. ON183968) of downy newlinemildew were genetically different correlated with 44.20 and 50.30 % disease severity, newlinerespectively. newlineTemperature range of 20 to 22 °C, relative humidity of 90 to 100 % was found newlinecongenial for sporangial (zoospore release) and zoospore germination of P. viticola at 24 newlineand 4 hrs after incubation in different photo (light and dark) periods. Temperature range of newline20 to 25 °C, relative humidity of 80 to 85 per cent favoured conidial germination of E. newlinenecator. Correlations of macro- and micro climate indicated