Variation of Avirulence Genes in the Blast Fungus from Jiangxi Province, China

The avirulence (<i>AVR</i>) genes of <i>Magnaporthe oryzae</i> are pivotal in eliciting resistance responses in rice, which are mediated by resistance (<i>R</i>) genes in rice. Monitoring the variation of <i>AVR</i> genes in the pathogen is essential for strategically deploying <i>R</i> 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 <i>AVR</i> genes in these isolates were analyzed by PCR amplification and sequencing. The results indicated that <i>AVR-Pi9</i>, <i>AVR-Pib</i>, <i>AVR-Pita</i>, and <i>AVR-Pizt</i> loci were detected in more than 95% of isolates. In addition, the <i>AVR-Pik</i> and <i>AVR-Pii</i> loci were found in 84.1 and 0.9% of isolates, respectively. Notably, none of the isolates contained the <i>AVR-Pia</i> gene. Sequencing results revealed various types of variants, including base replacement, deletion, and insertion, in <i>AVR-Pib</i>, <i>AVR-Pik</i>, and <i>AVR-Pita</i> loci. Moreover, a transposon insertion was identified in the promoter region of <i>AVR-Pib</i>. Furthermore, variant isolates were then utilized to inoculate the rice monogenic lines IRBLta-K1, IRBLkm-Ts, IRBLKh-K3, and IRBLb-B. The results demonstrated that the rice monogenic line carrying <i>Pib</i> or <i>Pita</i> was unable to recognize the isolates with the variant <i>AVR-Pib</i> or <i>AVR-Pita</i>. However, the rice monogenic line with <i>Pikm</i> or <i>Pikh</i> remained capable of recognizing the isolates with <i>AVR-Pik</i> 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.