Identification and Analysis of Avirulent Genotypes of Magnaporthe oryzae in Fujian Province from 2018 to 2020

  Objective  The pathogenicity and avirulent genotypes of Magnaporthe oryzae found in Fujian in recent years were analyzed to define their existence and year-to-year changes in different regions.

  Method  For the study, 179 strains of rice ear neck blast were collected from 9 major rice-producing areas in the province from 2018 to 2020 and isolated to identify the near-isogenic lines (NILs) that contained only one resistance gene.

  Result  Among the 179 rice blast strains, the proportion of strong, slightly strong, medium, and weak pathogenic classes were 26.81%, 36.31%, 27.37%, and 9.51%, respectively. Among the 4 high resistance genes, Pi-z⁵ and Pi-9(t) showed the greatest resistance frequencies of 91.49% and 91.25%, respectively, followed by Pi-k^h and Pi-1 of more than 80%. During the sampling years, the 9 avirulent genes produced more than 20% on frequency decline were Avr-k^h, Avr-7(t), Avr-5(t), Avr-3, Avr-k^p, Avr-19(t), Avr-k^m, Avr-z, and Avr-k^s. In the 23 types of avirulent genes, the pathogens with 6, 7, 8, 9, and 11 gene combinations had the highest appearance frequencies of 10.06%, 8.94%, 8.94%, 7.82%, and 8.38%, respectively. A total of 24 avirulent genes were identified in the rice blast strains found in the 9 regions that showed the highest frequencies of appearance at 49.19% in Shanghang, 48.18% in Guangze, and 41.23% in Wuyishan.

  Conclusion  Most rice blast strains in Fujian were strongly pathogenic to the 24 resistance genes, as discovered by this study. Among all, Pi-z⁵, Pi-9(t), Pi-k^h, and Pi-1 had the greatest frequencies of resistance, Avr-z⁵ and Avr-9(t) the most consistent over the years, and Avr-k^s, Avr-b, and Avr-ta the lowest with a frequency less than 20%. The corresponding avirulent genes could be useful for breeding, but the selection must be done with due caution.