菲律宾稻瘟病菌生理小种中AVR-Pita及其同源基因的序列与功能分析

根据已克隆的AVR-Pita及其同源基因序列设计4对引物，对来自菲律宾的74个稻瘟病单孢菌株DNA进行PCR扩增和序列分析，研究了与水稻抗病基因Pi-ta互作的稻瘟病菌无毒基因AVR-Pita及其同源基因序列多态性与进化关系。结果显示，在42个菌株中扩增出AVR-Pita1基因目的条带，31个菌株中扩增出AVR-Pita3基因目的条带，55个菌株中扩增出AVR-Pita4基因目的条带，但所有供试菌株均未扩增出AVR-Pita2基因目的条带。对PCR产物进行测序分析，发现AVR-Pita1基因在菲律宾的生理小种中存在序列多态性，可划分为5个单倍型，共有10个多态性位点；AVR-Pita3和AVR-Pita4基因序列较保守，序列比对后没有发现多态性。对不同单基因系接种鉴定，发现除第3种AVR-Pita1单倍型外，含有AVR-Pita1单倍型1、2、4及5的生理小种均不能与Pi-ta基因互作，从而使Pi-ta单基因系IRBLta-CT2在接种后表现为感病。以上试验结果说明AVR-Pita1基因变异性较强，且序列改变后会导致基因功能的变化。

The Sequence and Function Analysis of AVR-Pita Gene Family of Rice Blast Fungus,Magnaporthe oryzae in Philippines

For controlling rice blast and providing theory for breeding and selecting resistant rice variety, we studied the sequence polymorphism and function of avirulence gene AVR-Pita homologs. According to the cloned AVR-Pita homologs, we designed 4 primer pairs, selected 74 isolates from Philippine and distracted their DNA as template for PCR. The results showed that 42 isolates had the band of AVR-Pita1 gene, 31 isolates had the band of AVR-Pita3 gene, and 55 isolates had the band of AVR-Pita4 gene. However, no isolates showed the band of AVR-Pita2 gene. Sequences analysis of PCR products showed there were 5 haplotypes among AVR-Pita1 gene with variation in 10 base sites, while there was no polymorphic base site in AVR-Pita3 and AVR-Pita4 genes, indicating both genes were conservative. Inoculation tests demonstrated that IRBLta-CT2 was susceptible after inoculated with the haplotype 1, 2, 4 and 5, except haplotype 3. In conclusion, AVR-Pita1 gene is of strong variation, and its function will change after gene sequence has changed.