Analysis of Population Genetic Change to Single Oospore Strains of Phytophthora infestans

The occurrence of sexual reproduction accelerates the population genetic variation of Phytophthora infestans and makes it more difficult to control.The systematic analysis of the differentiation of phenotype(mating type and metalaxyl sensitivity)and genotype(mtDNA haplotype and SSR genotype)of 65 single oospore strains of P.infestans was carried out in this article.Five test strains were isolated from Heilongjiang Province and Mongolia Autonomous Region.The experiment results showed that the isolation ratio of metalaxyl resistance(MR:HR)of single oospore strains produced through the cross of medium resistance and high resistant parents was 18:13;the isolation ratio of the metalaxyl resistance(S:MR:HR)of single oospore strains produced through the cross of sensitive and high resistant parents was 4:12:7.The progenies of single oospore strains produced through self-fertility parents with medium resistance were all of the medium resistance.The mating types A1:A2 was greater than 1:1 in single oospore strains of the progenies,which did not conform to the Mendel's law of inheritance.All single oospore strains of the progenies inherited mitochondrial DNA fragments from only one parent.Sexual recombination of single oospore strains was verified by using two pairs of SSR primers(Pi4B and Pi4G).At the locus of Pi4B and Pi4G in the cross of KS-37 and KS-25,the separation frequencies of allele were 19:12 and 14:17,respectively.They produced two new genotype strains.This study could provide a basis for formulating disease control strategies.