Effectiveness and durability of the rice Pi-ta gene in Yunnan province of China

• Published in: Phytopathology 2014-10, p.PHYTO11130016Rtest
• Main Authors: Li, Jinbin, Lu, Lin, Jia, Yulin, Li, Chengyun
• Format: Article
• Language: English
• ISSN: 0031-949X

Rice blast is one of the most damaging diseases of rice worldwide. In the present study, we analyzed DNA sequence variation of avirulence genes of AVR-Pita1 in field isolates of M. oryzae in order to understand the effectiveness of the resistance gene Pi-ta in China. Genomic DNA of 366 isolates of M. oryzae collected from Yunnan province of China were used for PCR amplification to examine the existence of AVR-Pita1 using gene specific PCR markers. Results of PCR products revealed that 218 isolates of M. oryzae carry AVR-Pita1. Among of them, 62.5%, 56.3%, 58.5%, 46.7%, 72.4%, and 57.4% of M. oryzae carry AVR-Pita1 from northeastern, southeast, western, northwest, southwestern, and central of Yunnan province, respectively. The detection rate of AVR-Pita1 was in order as: southwest>northeast>western>central>southeast>northwest of Yunnan province. Moreover, a total of 18 AVR-Pita1 haplotypes encoding 13 novel AVR-Pita1 variants were identified among 60 isolates. Most DNA sequence variation was found to occur in the exon region resulting in amino acid substitution. Six virulent haplotypes of AVR-Pita1 to Pita were identified among 60 field isolates. The AVR-Pita1 has evolved to virulence from avirulent origins via base substitution. These findings demonstrate that AVR-Pita1 is under positive selection and mutations of AVR-Pita1 are responsible for defeating race-specific resistance in nature.