Identification by genetic analysis of two races of Erysiphe polygoni DC. causing powdery mildew disease in mungbean

Powdery mildew disease is one of the important foliar diseases of mungbean. Earlier, resistance sources have been identified and their genetic nature studied, but there is no information on race identification of Erysiphe polygoni so far. Different genotypes having combinations of the host resistance genes Pm₁Pm₁Pm₂Pm₂‘TARM‐1’, Pm₁Pm₁pm₂pm₂ (S‐158‐16) and pm₁pm₁Pm₂Pm₂ (S‐2‐4‐1) and no resistance genes pm₁pm₁pm₂pm₂ (TPM‐1) were used in the present investigation. The genotypes were screened with four isolates from Akola, Trombay, Jabalpur and Gauribidanur centres in India. The interactions of resistant differentials with the Akola isolate were different from the other three isolates. The inheritance patterns of different resistance genes in various crosses also differed with respect to the Akola isolate. The variation observed in the Akola isolate could be explained as the result of mutation of the dominant avirulence Avr₁Avr₁ genes to virulence avr₁avr₁ genes corresponding to host resistance Pm₁Pm₁genes. Therefore, the Akola isolate is identified as a second race of E. polygoni.