Chiang Mai Journal of Science

     Rice blast disease, caused by Magnaporthe oryzae, is a major threat to rice production worldwide and a critical concern in Vietnam, where rice is both a staple food and an economic crop. Effective management of this disease is essential for national food security and farmer livelihoods. This study investigated the morphological and genetic diversity of M. oryzae isolates collected from major rice-growing regions in Vietnam. Morphological analysis on V8 agar revealed variation in colony pigmentation, texture, growth rate, and melanin production, while conidia consistently displayed pyriform, 3-celled morphology. Genetic diversity, assessed using fifteen insertion–deletion (InDel) markers, showed moderate polymorphism with high discriminatory power. Phylogenetic and Principal Coordinates Analyses revealed population structures linked to geographic origin, host cultivar, and collection year. Southern isolates, mainly from the IR504 cultivar, formed a genetically uniform cluster indicative of recent clonal expansion, whereas northern isolates exhibited higher genetic heterogeneity. Vietnamese isolates were also genetically distinct from global reference strains, suggesting localized evolutionary dynamics. These findings advance our understanding of M. oryzae population genetics in Vietnam and provide valuable insights for developing region-specific management strategies and breeding programs to combat rice blast disease.