Identification of Resistance Genes Against Some Bacterial Blight Isolates of Rice

Five isolates collected from different parts of north western India were screened against seven standard differential cultivars and seventeen near isogenic lines (NILs) of rice in the background of IR 24 to differentiate between the virulence patterns of the isolates. Results thus, indicated considerable variability in virulence of the isolates. The fifth isolate was found to be highly virulent, while the fourth one was least virulent. On screening of the NILs, IRBB 8 was found to be moderately resistant to all the bacterial isolates. IRBB 21, carrying Xa 21 was found to be ineffective against the second isolate while IRBB 55 having high resistance exhibited quantitative complementation. Pyramided lines showed higher level of resistance than the single gene lines. All the bacterial isolates varied considerably in respect to their pathogenicity and virulence of which the fifth isolate was found to be most virulent.