Dynamics of Race Structures of Pyricularia oryzae Populations Across 18 Seasons in Guangdong Province, China

Rice blast, caused by Pyricularia oryzae, is one of the most damaging fungal diseases affecting rice. Understanding how the pathogen's race structure varies over time supports the efforts of rice breeders to develop improved cultivars. Here, the race structure of P. oryzae in Guangdong province, China, where rice is cropped twice per year, was assessed over 18 seasons from 1999 through 2008. The analysis was based on the reactions of a panel of seven differential Chinese cultivars to inoculation with a set of 1,248 isolates of P. oryzae in the province. The "total race frequency" parameter ranged from 14.7 to 39.7%, and the "race diversity index" ranged from 0.63 to 0.93. Twelve (ZA63, ZA31, ZA29, ZA21, ZA13, ZA9, ZB30, ZB17, ZB8, ZB2, ZC14, and ZC8) and two (ZD8 and ZD3) races were recognized as specific to indica and japonica rice types, respectively. Of the 59 distinct races identified, only two indica type races (ZC13 and ZC15) were identified as population-common, and nine indica type races (ZB1, ZB5, ZB6, ZB7, ZB13, ZB15, ZC5, ZC13, and ZC15) and one japonica type race (ZG1) were deemed to be population-dominant; the "total top two race isolate frequency" parameter ranged from 29.8 to 74.5%. On the host side, dynamics of resistance structures of the differential set were divided into three patterns: Both Tetep and Kanto 51 expressed the highest and most stable resistance, both Sifeng 43 and Lijiangxintuanheigu conveyed much lower and unstable resistance, and Zhenlong 13, Dongnong 363, and Heijiang 18 performed intermediate and seasonally dynamic resistance. Three interesting points distinguishing race structures of P. oryzae populations in southern and northeastern China were also discussed.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.