Variability studies of Magnaporthe oryzae Using International Rice Blast Differentials Set under Agroclimatic Conditions of Kashmir Valley, India

The pathogenic variability of the sixty isolates of M. oryzae was confirmed by testing them for virulence and cultivar reaction against International rice blast differentials (IBD) viz., Raminad Str. 3, Zenith, Usen, NP-125, Kanto-51, Dular, Tsia-tiao-sio and Caloro lodging Piz, Pia, Pii, Pia, Pika, Pi-k and Piks resistance genes for rice blasteither singly or in combination or with an unknown background. The pathotype analysis of the isolates, collected from four surveyed districts of Kashmir valley revealed the presence of four races viz., IC-17, IC-25, ID-1 and II-1 according to the race classification and nomenclature proposed by Ling and Ou (1969). Of the 60 isolates of M. oryzae, 25 isolates pertained to race IC-17, 16 and 14 other isolates pertained to race ID-1 and II-1, respectively, whereas four other isolates pertained to race IC-25. The predominant pathotype was IC-17 with a virulence frequency of 60 %, followed by II-1 (46.67%) in district Pulwama, ID-1 (40%) and IC-25 (13.33%) in district Bandipora, respectively. IC-17 was seen to be the predominant race in each location in every district. Race ID-1 has been observed to overcome the maximum number of genes viz., Pia, Pika+, Piks and Pik. but none of the isolates was able to overcome Raminad Str 3 and Zenith.