Transition of Race Distribution of Rice Blast Fungus in Korea over the Last Two Decades

Since the nationwide outbreak of rice blast disease caused by Magnaporthe oryzae in Korea in the late 1970s, the Korean unique race differential system was developed, and numerous studies on rice blast disease and rice blast resistance have been conducted to prevent the breakdown of blast resistance in rice varieties in the field. Race distribution and diversity of rice blast isolates have been identified over the past four decades through the Korean unique race differential system. The Korean unique race differential system, composed of eight different rice cultivars, can distinguish rice blast isolates into 15 KJ-races infecting Japonica-type varieties and 240 KI-races infecting Indica-, Indica/Japonica hybrid-, and Japonica-type varieties. This study revealed annual distribution and dynamics of the race structures of rice blast fungus in Korea from 1995 to 2020. A total of 128 races, comprising 15 KJ-races and 113 KI-races were shown, and the ratio of KJ isolates to KI isolates changed in cycles of 3-5 years over the past 26 years. This study also examined the transition of race diversity and the emergence of new races from 1995 to 2020, as well as the limits of the race differential system.