Genetic variability in the Indian maize germplasm for resistance to sorghum downy mildew (Peronosclerospora sorghi) and Rajasthan downy mildew (Peronosclerospora heteropogoni)

Downy mildews are among the most destructive diseases affecting maize production and productivity in various tropical Asian countries, including India. In view of the scarce information on genetic variability for resistance to sorghum downy mildew (Personosclerospora sorghi; SDM) and Rajasthan downy mildew (P. heteropogoni; RDM) in India, experiments were undertaken under rigorous artificial infection conditions during 1999 and 2000 at Mandya in Karnataka and Udaipur in Rajasthan, for characterization of the responses of 49 Indian maize inbred to the SDM and RDM pathogens, respectively. The study resulted in identification of an inbred line, NAI116 that offers high level of resistance to both the downy mildews, besides ten inbred lines that offer resistance to RDM. However, majority of the Indian maize inbreds were vulnerable to both SDM and RDM. Two inbred lines, KUI1411 and KUI1414A, which were reported to be resistant to P. zeae in Thailand, displayed high susceptibility to SDM and resistance to RDM. Identification of a stable source of resistance to major downy mildew diseases in India offers opportunities for undertaking detailed genetic and molecular analyses of downy mildew resistance.