Study of post-flowering stalk rot (PFSR) pathogen species variation and possible shifts across selected maize agro-ecologies in South Asia

Post-flowering stalk rots (PFSR) are reported from all major maize growing ecologies, and are caused by at least six genera of fungal pathogens, which generally occur as a complex, along with secondary colonizers (Afolabi et al., 2008). PFSR are expected to be exacerbated by the changing climates in Latin America, Asia and Sub-Saharan Africa, especially increases in temperature. The level of impact is determined by a number of factors, including the weather during the growing season, the amount of stress on the plants, hybrid genetics and the populations of the stalk rot pathogens in the field. In Asia, PFSR is reported from many countries, including Nepal, Cambodia, China, India, Indonesia, Laos, Pakistan, Philippines, Thailand and Vietnam (Lal and Singh, 1984; Yang et al., 2010; Subedi et al., 2016). Among the different stalk rots in the complex, Fusarium stalk rot (FSR), Charcoal rot (CR) and Late wilt, are more prevalent and destructive in the Asian tropics (Khokhar et al., 2014). Due to the complex nature of the stalk rot complex, with multiple primary and secondary infections, we still do not have comprehensive understanding of the prevalence and spread of the stalk rot pathogens in different maize agro-ecologiesin Asia. This limits the capacity to plan defensive strategies, including development and deployment of resistant varieties. As these diseases affect the crop, at a much later stage in the life cycle, the economic impact of the disease is high, and hence is one of the biggest challenges faced by small and marginal farmers. Hence, characterizing the pathogen spectrum that causes this disease is important towards planning of IPDM strategies including resistance breeding. Hence this study is being undertaken in maize growing areas in India and Nepal as part of Work Package 2 of PHI contributing to Output-6 (WP2-OP6: Knowledge on P&D shifts and virulence variation with strategies for augmenting IPDM and resistance breeding).