Study On Phenotype And Multi-locus Genotype Of Phytophthora Infestans

Potato late blight is an important disease that damages potato production.The study on phenotype and multi-locus genotype of phytophthora infestans has important significance for the prevention and control of late blight and the establishment of a comprehensive prevention and control strategy.A total of 145 Phytophthora infestans isolates collected from Heilongjiang province in2015²017 were determined for mating type and sensitivity to metalaxyl.The results showed that three mating types were found in 145 P.infestans.A₁,A₂ and self-fertility were accounted for88.3%,5.5%and 6.2%of the total isolates,respectively.According to the analysis of collection years,the distribution pattern of P.infestans collected from Heilongjiang province became complicated year by year.According to the analysis of collection sites,all the P.infestans isolates collected in Harbin were A₁ mating type,while A₁,A₂ and self-fertility were found the P.infestans isolates collected from Suihua and Qiqihar city.The results indicates that there was no sexual reproduction of P.infestans isolates collected in Harbin,but the P.infestans isolates collected from the other two main producing areas can be carried out sexual reproduction.The results of sensitivity to metalaxyl showed that 96.6%isolates were resistant to metalaxyl and 3.4%isolates were moderate resistant to metalaxyl.The results of sensitivity to metalaxyl test of P.infestans in Heilongjiang province from 2015 to 2017 showed that P.infestans the collected are all resistant.Thus,the proportion of metalaxyl resistance isolates increased year by year.The results suggested that P.infestans isolates occur in Heilongjiang province have been produced metalaxyl resistance.In this study,the genetic diversity of P.infestans was determined by using mtDNA haplotypes and SSR genotypes.For mtDNA haplotype analysis of P.infestans,two mtDNA haplotypes of Ia and IIa were found,and the dominant mtDNA haplotype is IIa.The SSR genotype of P.infestans isolates collected from Heilongjiang province were analyzed by using two pairs of primers.The results showed that seven genotypes were identified,namely F-01,F-02,F-03,F-05,F-06,D-02and G-02,and the dominant SSR genotype is F-01.According to the mtDNA haplotype and SSR genotype,total of 9 multi-locus genotypes were divided in Heilongjiang province in 2015²017.From the analysis of collected years,the multi-locus genotype A was the dominant genotype among the isolates collected from 2015 to2017.The pathogenicity of 9 multi-locus genotypes was analyzed according to the area of infected leaf,the amount of sporulation and frequency of infection.The infection area,the amount of sporulation and infection frequency of the three genotypes which was multi-locus E,multi-locus F and multi-locus I were higher than those of other genotypes.The above results showed that the three genotypes had stronger pathogenicity than other genotypes.Multi-locus C genotypes were the lowest in area of infected leaf,the amount of sporulation and frequency of infection.The result indicated that the pathogenicity of multi-locus C genotype was weakest among the 9 genotypes.When the genotypes are the same,the mating type can also cause the difference of the pathogenicity.The results above indicated that the population structure of P.infestans collected from Heilongjiang province in 2015²017 became complicated year by year.The population structure of P.infestans collected from Suihua city was the most complicated compared with the other two regions.Therefore,Suihua city may be the origin center of Potato late blight in Heilongjiang province.In the future,the monitoring of potato late blight should be strengthened in this region.