| Late blight,caused by P.infestans(Mont De Bary)is a destructive Oomycetes disease,which had a serious damage to the potato production and production with occurrence and prevalence.Many countrys had reported that P.infestans had fungus resistance to Metalaxyl,since Metalaxyl was first put into prevention and control P.infestans in the late 1970s.So it is crucial to explore the resistance mechanism and population differentiation.This experiment according to SSR geneotype from different place in China(Yunan,Guangxi,Guizhou,Ningxia,Gansu,Shanxi,Fuzhou and Xiapu)had screened of a total 141 strains of P.infestans.By measuing P.infestans resistance level,pathogenicity and analysis genetic diversity of the Metalaxyl function target gene RPA 1(DNA-directed RNA Polymease I Subunit).To explore P.infestans in Metalaxyl resistance,pathogenicity and analysis target genetic diversity and resistance mechanism,providing theoretical basis for effective sustainable control of P.infestans,The results are as follows:1.Metalaxyl is a kind of benzene amide fungicides.In the experiment,we used the theory of common garden to test the resistance of P.infestans at five concentraion(5,10,50,100,200,μg/mL),the result showed different relatve growth rate(RGR)under the same concentration of Metalaxyl and different concentrations.RGR was inhibited with the increase of Metalaxyl concentration.Median lethal concentration(EC50)ranged from 0.002 to 490.19,it is significant difference between eight populations in EC50(F=17.245,p<0.000),the sensitivity baseline was unimodal,resistance isolates arrive to 85.6%,intermediate is 9.8%and sensitive is only 4.2%.Eight population were resistant to Metalaxyl.2 Spore suspension was used to test pathogenicity,the results showed all p.infestans strains infected potato leaves successfully,different strains could caused different plaque and different incubation period(p<0.001),which means correlation between geographical origin and pathogenicity p.infestans different.3.Through the RPA 1 gene sequence analysis,all populations nucleotide diversity(π<0.5%),In addition to Yunnan population haplotype diversity(Hd)was greater than 0.5,other populations lesser than 0.5.Fuzhou and Xiapu populations had the highest hapltype diversity and Yunnan population had the lowest.The pairwise population differentiation(FST)were greater than 0.15,Shanxi had the largest FST between another populations,the FST between Yunnan,Gansu and Ningxia popultion were lowest.Based on KST,Z and Snn three tests revealed significant differentiation between populations.The analysis of correlation between ATP6 gene and geographical(altitude,longtide and mean temperature of air)factors.The result showed that there are only two haplotype,it is significantly between Hapl-1 proportion and altitude,mean temperature and lontide(r=-0.894,p=0.007),(r=-0.752,p=0.051),Hapl-2 conclusion instead.The degree of genetic differentiation between groups(FST)and the linear distance between groups was significantly positively related(r=0.659,p=0.001).This study showed that ATP6 gene haplotype distribution and group had a significant correlation between geographical factors... |
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