广东省侵染美香占2号的稻瘟病菌致病性及无毒基因变异分析

[目的]分析侵染广东稻区优质品种美香占2号稻瘟病菌(Magnaporthe oryzae)的致病性及无毒基因变异特征,为美香占2号在不同稻区的合理布局提供参考依据.[方法]利用9个抗稻瘟病单基因系,对稻瘟病菌单孢分离菌株进行致病性测定;并利用8个稻瘟病菌已克隆无毒基因的功能性分子标记对2013-2018年不同年份、不同...

Pathogenicity and Avirulence Genes Variation of Magnaporthe oryzae from a Rice Variety Meixiangzhan 2 in Guangdong Province

【Objective】The objective of this study is to analyze the pathogenicity and variation patterns of avirulence genes (Avr genes) genotype of Magnaporthe oryzae, which was collected from a high-quality rice variety Meixiangzhan 2 widely cultivated in Guangdong, and to provide a reference for the rational layout of Meixiangzhan 2 in different rice ecological areas. 【Method】The pathogenicity of single-spore strains was determined using 9 M. oryzae monogenic differentials. The DNA of the single-spore M. oryzae strains collected from Meixiangzhan 2 in different rice areas and in different years from 2013 to 2018 was subjected to PCR amplification using the functional markers of 8 Avr genes. The PCR products of Avr genes with promotor sequences or CDS regions were analyzed by agarose gel electrophoresis and the PCR products of representative strains were sequenced, and their sequences were compared to corresponding Avr genes, respectively. The corresponding M. oryzae monogenic differentials were used to determine the pathogenicity of M. oryzae strains with different mutation types of the Avr genes. According to two mating types MAT1-1 and MAT1-2 molecular markers of M. oryzae, the possible mating type of M. oryzae strains isolated from Meixiangzhan 2 was detected. 【Result】The pathogenicity analysis with a set of monogenic differentials showed that 52 rice blast strains collected from Meixiangzhan 2 from 2013 to 2018 were avirulent to IRBL9-W (Pi9), IRBLzt-T (Piz-t), NIL-e1 (Pi50) and IRBLkh-K3 (Pikh). The tested strains showed high frequencies (>57%) of virulence to IRBLz-Fu (Piz), IRBLkp-K60 (Pikp) and IRBLi-F5 (Pii), and the frequency of virulence to IRBLz-Fu (Piz) showed significant differences in different years, suggesting that the M. oryzae population in the field of Meixiangzhan 2 planted area had a higher frequency of virulent strains of avrPiz, avrPikp and avrPii. AvrPiz-t, AvrPi9 and AvrPik-CDE fragments were almost present in all tested strains, but none of Avr1-CO39, AvrPia or AvrPii was amplified in any strain. Only 4 strains could amplify the fragment of AvrPita, and only 3 strains could amplify the fragment of AvrPik-ABF. Amplicon sequencing of the 7 strains revealed that the sequences of AvrPi9 and AvrPiz-t were identical to those of the corresponding Avr genes. Of the 7 sequenced strains in AvrPik-CDE, 4 strains were almost identical to each other, and 3 strains had a ‘CTTT' in the coding region of AvrPik. Four different amplification types of AvrPib (expected size bands, bands with transposon Pot3 insertion, bands with transposon Mg-SINE insertion, and non-amplified bands) were detected by electrophoresis analysis and 5 different haplotypes (AvrPib-AP1-1, AvrPib-AP1-2, avrPib-AP2, avrPib-AP3 and avrPib-AP2+avrPib-AP3) were detected by sequencing PCR products. The genotypes AvrPib-AP1-1 and AvrPib-AP1-2 were avirulent, while avrPib-AP2 and avrPib-AP3 showing insertions of transposon Pot3 or Mg-SINE with different insertion sites were virulent. A double haplotype of avrPib-AP2+avrPib-AP3 was detected in one strain. The result of mating type analysis with molecular markers showed that all of 52 tested strains belonged to the mating type of MAT1-2, two strains (GD18-009 and GD18-185) from Shaoguan, Guangdong were also detected with MAT1-1 mating type, indicating that these two strains had dual mating types. 【Conclusion】Among the strains from the high-quality rice variety of Meixiangzhan 2 in Guangdong, the Avr genes of AvrPiz-t, AvrPi9, AvrPi50 and AvrPikh distribute widely. The variation types of AvrPib are abundant. The results of this study will provide useful information for the rational layout of Meixiangzhan 2 and the deployment of other rotation varieties with different genotypes of rice blast resistance.