Confirmation of physiological race of Bipolaris maydis causing maydis leaf blight of maize in India

Maydis leaf blight (MLB) incited by Bipolaris maydis occurs in most of the maize growing regions. Present study revealed morphological divergence among 74 isolates of B. maydis collected from geographically distant places of India. Based on morpho-cultural features clustered by R software, 25 representative isolates of B. maydis were used for race identification. The internal transcribed spacer (ITS) sequence further confirmed the isolates as B. maydis. In recent concept, variation in disease incidence and infectivity denotes genetic shift in the pathogen or introduction of new pathogenic race(s) through germplasm exchange. For unveiling Indian race(s) of B. maydis, present exploration was made. Four genetically divergent maize genotypes with cytoplasmic male sterility (CMS), viz. -C (MGU- 161QPV-C), -T (MGU- 345PV-T), -S (MGU-150Q-S) and CM-119 (fertile cytoplasm) were assessed using 25 isolates of B. maydis during kharif 2018–19 at ICAR-IARI, New Delhi. The genotype MGU-161QPV-C associated with CMS-C was highly resistant followed by MGU-345PV-T (CMS-T) and MGU-150Q-S (CMS-S), whereas CM-119 showed high susceptibility. Present outcome confirmed prevalence of race ‘O’ of B. maydis in India and eliminated uncertainty about occurrence of other races, i.e. T and C.