The Genetic Diversity Of Phytophthora Infestans In Guizhou Province

Potato late blight caused by Phytophthora infestans is the most serious disease in potato production,which affects potato quality and yield.To understand the composition of phenotype,genetic structure and the level of genetic diversity of P.infestans could provide an important scientific basis for the effective control of this disease.In recent years,there are deep studies on the origin,migration,occurrence,prediction and prevention of this disease,but there is not a systematic study on potato late blight in Guizhou province.In this paper,we use the method of differential hosts,molecular biology method combined with confrontation culture,PCR-RFLP,SSR molecular marker technology to study the 74 P.infestans strains that were isolated from 32 counties of Guizhou province in 2008 and 2017-2018 respectively and 54 that were isolated from Hezhang,Mainly from four aspects to describe the population structure characteristics,analysis of genetic diversity by the physiological race,mating type,mitochondrial DNA haplotypes,SSR genotype.1.The results showed that 18 physiological races were found in 74 P.infestans strains by the identification host method in Guizhou province,among them,2.4.6.8.9 is the dominant species,accounting for 17.75%,and the widest geographical distribution.only one single gene type physiological race were detected,its composition was 2,a total of 3 strains,accounting for 4.05%,distributed in Shuicheng and Panxian.The physiologyical races with the lowest frequency are 2.3.4.6.10,2.3.4.6.9 and 2.4.5.6,and all their frequencies are 1.35%.2.Two pairs of primers S1,PHYB,combined with confrontation culture method ware used to study the mating type of the 74 P.infestans strains,The results show that the A1 mating type strains are 36 strains in Guizhou,A2 mating type strains are 36 strains,A1A2 mating type strains are 2 strains,accounted for 28.13%,70.31%,1.56% respectively,there is diversity.3.Choose two pairs of primers(F2,R2,F4,R4)to identify the mitochondrial DNA haplotypes of the 74 P.infestans strains,The results showed that Two types of mitochondrial DNA haplotypes were detected,I a type and II b type.Among them,Ia type is 47 strains,IIb type is 27 strains,accounted for 63.51%,36.49% respectively.Ia is from Duyun,Puan,Shuicheng,Puding,Panxian,Weining,Xifeng,Zunyi,Yanhexian,Nayong,Zhijin,Jinsha,QianXi,Bijie,Hezhang,Xingyi,TongZi,Xiuwen,Dejiang,Meitan respectively,IIb type is from Libo,Pingba,Puding,Liuzhi,Zunyi,Sandu,Huaxi,Dejiang,Huishui,Sansui,Fuquan,Rongjiang,Tianzhu,Dafang,Weining respectively,the regions of having Ia type and type IIb the same time are Puding,Zunyi,Weining.4.Seventeen pairs of SSR primers were used to carry out polymorph amplification on 74 strains in Guizhou province,and one strain from CBS,SSR molecular markers showed that Polymorphic bands were amplified with 16 pairs of primers,accounting for 94.12%;the population genetic diversity index is 0.3989 and gene flow is 1.1049;the results of genetic structure showed that the optimal K value of the 10 groups is 6,which could be divided into 6 subgroups with different proportions;the genetic distance results showed that the genetic distance between guizhou bacterial populations is different,mostly between 0.9004-0.9936,and small between 0.8841-0.8947;the clustering results showed that when the genetic coefficient is 0.974,it could be divided into five branches.The above SSR molecular marker data indicated that the Phytophthora infestans in Guizhou province has genetic diversity.There are abundant physiological subspecies,10 physiological races were found in 54 P.infestans strains in Hezhang,There is diversity.from the relationship between the physiological races and the host,there is no correlation between the physiological races type and the host,That is to say,the physiological races type of different strains on the same host might be the same or different,and different strains on different hosts might be the same or different.From the relationship between the mating type and the host,the mating type of 54 P.infestans strains in Hezhang is A2,they not have diversity,That is to say,there is no correlation between the mating type and the host.From the relationship between the mitochondrial DNA haplotypes and the host,the mitochondrial DNA haplotypes of 54 P.infestans strains in Hezhang is Ia,they not have diversity,That is to say,there is no correlation between the mitochondrial DNA haplotypes and the host.From the relationship between the genetic diversity of SSR molecular markers of 54 strains with their hosts in Hezhang,54 strains were classified into 29 populations according to host varieties,all strains showed no diversity and no correlation with host varieties.According to the overall analysis of physiological race,mating type,mitochondrial DNA haplotypes type and the genetic diversity of the SSR molecular marker of Guizhou potato late blight bacteria,they have diversity.