海南省田间稻瘟病菌中AvrPiz-t基因位点变异

Variations of the AvrPiz-t gene locus in field Magnaporthe oryzae strains collected from Hainan Province

为评估在水稻育种中被广泛利用的广谱抗稻瘟病基因Piz-t的有效性,对不同年份分离自海南省陵水黎族自治县和三亚市水稻的273株田间稻瘟病菌株中的AvrPiz-t位点变异及其与菌株致病性的相关性进行系统研究。结果表明,海南省田间菌株中无毒基因AvrPiz-t位点的变异频率为0~100.00%,陵水黎族自治县菌株中的变异频率远远高于三亚市菌株。在菌株中共鉴定到3种AvrPiz-t位点变异类型,分别为基因位点完全缺失、DNA重复元件MGR583在基因位点启动子区-10 bp上游和编码区218 bp下游插入。所有AvrPiz-t位点变异的菌株对携带Piz-t抗病基因的单基因水稻系IRBL-11均表现出强的致病性。陵水黎族自治县菌株中AvrPiz-t位点的变异频率呈逐年增加趋势,2021年94株菌株中AvrPiz-t位点的变异频率为100.00%,其中51.06%的菌株变异是MGR583在启动子区-10 bp上游插入,表明DNA重复元件MGR583在AvrPiz-t位点插入是AvrPiz-t从无毒到有毒进化的重要机制之一。

To evaluate the effectiveness of the broad-spectrum blast resistance gene Piz-t widely used in rice resistance breeding,the investigation of AvrPiz-t(the Magnaporthe oryzae avirulence gene)locus variation in 273 field strains collected from Lingshui and Sanya of Hainan Province were carried out,and the correlation between pathogenicity and AvrPiz-t locus variation of strains was analyzed.The results showed that the variation frequency of AvrPiz-t locus in Hainan field strains ranged from 0 to 100.00%,and the variation frequency in the isolates from Lingshui was much higher than that in the isolates from Sanya.Three variant types of AvrPiz-t locus were identified in 273 field strains,including whole-gene deletion,the insertion of the repeat DNA element MGR583 at 10 bp upstream or 218 bp downstream from the transcription start site(TSS).All the tested isolates with variant AvrPiz-t locus were virulent to the monogenic rice line IRBL-11 containing cognate R gene Piz-t.The variation frequency of AvrPiz-t locus among the Lingshui isolates displayed a rising trend year by year.It is noteworthy that the variation frequency of AvrPiz-t locus in the 94 isolates collected from Lingshui in 2021 was 100.00%,of which,51.06%was caused by MGR583 insertion at 10 bp upstream from the TSS.The results indicated that the insertion of the DNA element MGR583 at AvrPiz-t locus was one of the important factor driving evolution of the blast fungal isolates in Hainan field from avirulence to virulence to the blast resistance gene Piz-t.