海南稻作区稻瘟病菌AvrPik等位基因的变异监测与多样性分析

海南省地处热带。由于具有国内其他地区无可比拟的光温资源优势，每年有大量的水稻材料在南繁区繁育与种植，给稻瘟病菌的变异及传播带来了极大的便利。自20世纪70年代以来，Pik等位基因已被广泛地用作水稻抗稻瘟病育种的主要抗源。为了解海南稻瘟病菌AvrPik等位基因的变异及多样性，本研究从海南稻作区采集穗茎瘟病样，通过单孢分离获得100株稻瘟病菌株。利用AvrPik基因特异性引物扩增病原菌DNA,所得PCR产物经克隆、测序后与参考序列进行比对分析。结果从100株菌株中鉴定出AvrPik＿A、AvrPik＿B、AvrPik＿D、AvrPik＿E和AvrPik＿F共5种等位基因类型。其中AvrPik＿D类型最多，出现频率为50.00%;其次为AvrPik＿E类型，出现频率为32.08%;第三为AvrPik＿B类型，出现频率为8.49%。在AvrPik等位基因核苷酸多样性方面，非信号肽区域多样性要明显高于信号肽区域。就群体受到的选择压而言，南繁种植区与常规种植区的稻瘟病菌群体的Ka/Ks值均大于1,分别为2.703 1和1.236 6,表明，无论是南繁区还是常规种植区，AvrPik等位基因均受到了强...

Variation monitoring and diversity analysis of AvrPik alleles of Magnaporthe oryzae in rice-growing areas of Hainan

Hainan province is located in the tropical region. Because of the incomparable advantages of light and temperature resources in Hainan over the other regions in China, a large number of rice varieties are bred and planted in off-season breeding areas in Hainan every year, which brings great convenience to the variation and transmission of Magnaporthe oryzae. The major resistant gene Pik for rice blast and its alleles have been extensively exploited as sources of genetic resistance in rice breeding programs since 1970s. In order to understand the variation and diversity of AvrPik alleles in Magnaporthe oryzae in rice-growing areas of Hainan, 100 M. oryzae strains were isolated from the rice growing areas of Hainan. The AvrPik genes were cloned from the genomic DNA, sequenced and then compared with the reference sequences. Finally, five main allele genotypes including AvrPik_A, AvrPik_B, AvrPik_D, AvrPik_E and AvrPik_F were identified. The frequencies of AvrPik_D, AvrPik_E and AvrPik_B were 50.00%, 32.08%, 8.49%, respectively. In terms of the nucleotide diversity of AvrPik alleles, the nucleotide diversity of non-signal peptide regions was obviously higher than that of signal peptide regions. In terms of selection pressure on populations, the Ka/Ks ratios of M. oryzae populations from off-season breeding area and the conventional cultivation area were all greater than 1 (2.703 1 and 1.236 6, respectively). These results indicated that AvrPik alleles in both growing areas were subjected to strong positive selection pressure, and the pressure on AvrPik alleles in off-season breeding area were stronger than that in the conventional area. The hypha of strain 20MG48 (AvrPik_F) grew fastest, but its spore production was the least among the five representative strains. The population structure of Avrpik alleles was preliminarily clarified in rice-growing areas of Hainan province, which provides a reference for the planting of resistant varieties and the breeding program for blast resistance in the rice growing area.