Disease Incidence and Race Diversity of Rice Blast in Korea from 2020 to 2022

Rice blast is a devastating disease, caused by Magnaporthe oryzae, and presents a significant challenge to rice production, impacting leaves, nodes, stems, necks, and panicles throughout the growing season. To enhance sustainable rice production and effective disease management, it is crucial to continuously monitor rice blast incidence and race diversity. An increase in the incidence of rice blast disease in Korea in 2020 and 2021 has been reported, leading to a decline in rice production, particularly in Jeonbuk, where both leaf blast and panicle blast were prevalent. In this study, the incidences of rice leaf blast and panicle blast were monitored nationwide from 2020 to 2022 and race diversity and pathogenic characteristics of 754 rice blast isolates collected from leaves and necks were identified. Among these, the race distribution of 633 isolates was classified according to the resistant reactions of the Korean differential race system. Applying the Korean differential race system, the isolates were categorized into 40 different unique Korean races distinguishing the ability to cause disease in Japonica-type and Indica-type cultivars. Moreover, pathotype analysis of 556 isolates using the monogenic resistance lines showed that most of the evaluated isolates had incompatible reactions to monogenic lines carrying the resistance genes Pita-CP1, Piz-t, and Piz-5. The similarity of the pathotypes among the isolates was analyzed based on the disease reactions of the monogenic resistance lines, and 28 isolates were selected as a standard representative set considering their viability, high virulence, dominant Korean races, and different reactions to resistance genes. This comprehensive study aims to inform the development of durable blast protection and provide valuable insights for breeding broad-spectrum-resistant rice cultivars.