INHERITANCE OF POWDERY MILDEW (ERYSIPHE POLYGONI DC) RESISTANCE IN MUNGBEAN (VIGNA-RADIATA L WILCZEK)

Detached mungbean (Vigna radiata L. Wilczek) leaves were inoculated wi th a conidial suspension of a local isolate (TI-1) of the powdery mild ew pathogen (Ery-siphe polygoni DC) under controlled environment condi tions. Based on the latent period and severity of the infection, a rat ing scale of 0-5 was used to classify the host pathogen interactions. Reactions O, 1 and 2 were considered resistant and referred to as R0, R1 and R2 while 3, 4 and 5 were classified as susceptible (S). RUM lin es (resistant to powdery mildew) and their derivatives are crossed wit h several susceptible (reaction types 3-5) genotypes and the inheritan ce of the resistance was studied in the F-1, F-2 and F-3 generations. The results showed that powdery mildew resistance in mungbean is gover ned by two dominant genes designated as Pm-1 and Pm-2. When both Pm-1 and Pm-2 were present, an R0 reaction was observed after inoculation w ith TI-1. The resistant reaction was R1 when only Pm-1 was present and R2 in the presence of Pm-2. In the absence of both Pm-1 and Pm-2, sus ceptible reactions 3, 4 and 5 were observed.