致病疫霉有性生殖诱导及F1代遗传多样性

Sexuality induction and genetic diversity analysis of the F1 progenies of Phytophthora infestans

致病疫霉Phytophthora infestans为马铃薯晚疫病的重要病原菌。通过从昆明市寻甸县采集110P和H-6两株致病疫霉,明确其染色体倍性、交配型、线粒体单倍型、毒性和甲霜灵敏感性,经对峙培养,利用改良的卵孢子萌发方法获得有性生殖F1代群体POP1(60株),并对POP1进行表型和基因型测定。结果表明:冷冻处理24h为最佳条件,卵孢子萌发率达5.09%±0.15%;POP1的交配型、毒性和甲霜灵敏感性均发生了分离,其中交配型分离比为A1:A2:A1A2:自育型(SF)=16:5:17:22,毒性分离比为抗性(R):敏感性(S)=11:49,甲霜灵敏感性分离比为抗性(R):敏感性(S)=2:58;3个表型的分离均偏离孟德尔单基因显性遗传特点。基于8对SSR多态性引物对POP1基因型分析表明,遗传相似系数为0.98时,可将所有菌株分为14个基因型;遗传相似系数为0.95时,可将POP1分为6个分支,其中优势群体为S1,占分离群体的61.67%。关联分析进一步表明,8对SSR所代表的基因型和几个重要表型有显著相关性(R2=0.6667)。本研究建立了高效的致病疫霉卵孢子萌发体系,解析了有性生殖后代群体遗传结构特点,为深入探索致病疫霉的变异规律及病害流行趋势提供了理论基础。

Phytophthora infestans caused serious potato late blight disease. In this study, two isolates of P.infestans, 110 P and H-6, collected from Xundian district in Kunming city, were used to determine the chromosome ploidy, mating type, mitochondrial DNA, virulence and metalaxyl sensitivity. The improved oospore germination method was developed and used to obtain sexual reproduction F1 progenies POP1(60 isolates). The phenotype and genotype of POP1 were also identified. The results show that freezing treatment for 24 h is optimal for oospore germination and the germination rate may reach 5.09%±0.15%. Non-mendelian segregation pattern was manifested in 3 phenotypes of POP1, mating type, virulence and metalaxyl sensitivity.The mating type separation rate is 16:5:17:22(A1:A2:A1 A2:SF), the virulence separation rate is 11:49(R:S),and the separation rate of sensitivity to metalaxyl is 2:58(R:S). Genotype analysis using 8 pairs of SSR primers showed that a total of 14 genotypes was detected in POP1 when the genetic similarity coefficient was equal to0.98. POP1 could be divided into six clades at the genetic similarity coefficient of 0.95, and the dominant lineage is S1, accounting for 61.67% isolates in POP1. The relationship analysis revealed significant correlation between genotypes and phenotypes(R2=0.6667). This study established an efficient oospore germination method of P. infestans and analysed population genetic structure by using sexual reproduction offsprings,providing a reference for further understanding the variation characters of P. infestans and predicting the epidemic trend of the late blight disease.