The pathogenicity and genetic diversity of the Indonesian blast pathogen from wide host ranges of rice sub-species

This study investigated the genetic diversity and pathogenicity of Pyricularia oryzae isolates collected from rice resistance lines in Lampung, Sukabumi, and Banyumas, Indonesia. A total of 38 isolates were collected, with the majority from Lampung. Pathotype variation analysis revealed diverse races across the regions, with significant differences in susceptibility observed among rice varieties. SSR markers showed four clusters based on host introgression types. Avr-ACE1 and mating type markers revealed clustering by geography and mating type. SNP markers indicated distinct relationships in rice hosts, particularly Banyumas and Sukabumi rice with Indica, Indica-Oryza rufipogon, and Japonica-Indica-O. rufipogon introgression, showing close relatedness. In contrast, Lampung rice, dominated by the J type of introgression, formed a separate cluster and exhibited the highest diversity of Avr-ACE1 alleles and mating types, suggesting strains with extensive resistance gene introgression are suitable for cultivation. Parasexual recombination was identified as the primary mechanism for DNA exchange in P. oryzae. Host responses indicated the Cisokan variety's resistance to all blast pathogens, highlighting its potential as a donor for blast resistance in local rice improvement programs. These findings contribute to understanding the genetic interactions between P. oryzae and rice hosts, aiding in the development of more effective blast disease management strategies.