VIRULENCE DIVERSITY IN NORTH INDIAN ISOLATES OF SCLEROSPORA GRAMINICOLA THE PEARL MILLET DOWNY MILDEW PATHOGEN
R. Sharma, V.P. Rao, S. Senthilvel, S.C. Rajput, R.P. Thakur
On-farm surveys were conducted in the Uttar Pradesh (India) during the two rainy seasons 2007 and 2008 to monitor pearl millet (Pennisetum glaucum) downy mildew incidence. Twenty-one isolates of Sclerospora graminicola, the pearl millet downy mildew pathogen, were collected from different hybrid cultivars. These isolates were established on seedlings of the highly susceptible line 7042S grown in the greenhouse and were characterized for their virulence diversity using a set of seven host differential lines. Quantitative differences in virulence among pathogen isolates were determined by calculating virulence index (percent disease incidence × latent period-1). Results were submitted to cluster analysis using the Average Linkage method to determine similarity among pathogen isolates. The two highly virulent isolates, Sg 492 from Aligarh and Sg 510 from Badaun, representing geographically diverse locations were selected for use in greenhouse screening of pearl millet breeding lines.