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

Detached mungbean (Vigna radiata L. Wilczek) leaves were inoculated with a conidial suspension of a local isolate (TI-1) of the powdery mildew pathogen (Ery-siphe polygoni DC) under controlled environment conditions. Based on the latent period and severity of the infection, a rating 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 lines (resistant to powdery mildew) and their derivatives are crossed with several susceptible (reaction types 3-5) genotypes and the inheritance 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 governed 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 with 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, susceptible reactions 3, 4 and 5 were observed.