Variation of avirulence genes in the blast fungus from Jiangxi Province, China

The avirulence (AVR) genes of Magnaporthe oryzae are pivotal in eliciting resistance responses in rice, which are mediated by resistance (R) genes in rice. Monitoring the variation of AVR genes in the pathogen is essential for strategically deploying R genes in rice cultivation regions. In this study, a total of 214 isolates were collected from Jiangxi Province, China, in 2022, and the distribution and variation of AVR genes in these isolates were analyzed by PCR amplification and sequencing. The results indicated that AVR-Pi9, AVR-Pib, AVR-Pita, and AVR-Pizt loci were detected in over 95% of isolates. In addition, the AVR-Pik and AVR-Pii loci were found in 84.1% and 0.9% of isolates, respectively. Notably, none of the isolates contained the AVR-Pia gene. Sequencing results revealed various types of variants, including base replacement, deletion, and insertion, in AVR-Pib, AVR-Pik, and AVR-Pita loci. Moreover, a transposon insertion was identified in the promoter region of AVR-Pib. Furthermore, variant isolates were then utilized to inoculate rice monogenic lines IRBLta-K1, IRBLkm-Ts, IRBLKh-K3 and IRBLb-B. The results demonstrated that the rice monogenic line carrying Pib or Pita was unable to recognize the isolates with variant AVR-Pib or AVR-Pita. However, the rice monogenic line with Pikm or Pikh remained capable of recognizing the isolates with AVR-Pik alleles in Jiangxi Province. The information obtained from this study is valuable for breeding blast-resistant rice varieties that will be cultivated in Jiangxi Province, China.