Phytophthora Infestans Population Genetic Structure And Phylogenetic Analysis Of Avirulence Gene Avr3a

The late blight caused by Phytophthora infestans, is one of the world important devastating disease. Disease prevention and control is rely mainly on resistant varieties and use of chemical agents in currently.For not only increase the cost of chemical control but also cause environmental pollution. Cultural control of potato late blight resistant varieties is the most cost-effective method, but due to variable P. infestans populations, resistant to the loss of resistant varieties. Clear P. infestans population genetic structure and variation, can find new disease prevention measures to develop sustainable disease control strategies provide a theoretical basis.Study on the genetic phenotype of the 80 P. infestans collected from the Ningde Zhouning suburbs, the results showed:highly resistant strains of metalaxyl and resistant strains of metalaxyl accounted for 90%and 10%respectively, metalaxyl-sensitive strains was not found; the 80 tested P.infestans all were Al mating type, there was not A2 mating type, A1A2 mating type and self-sterile strain. Mitochondrial DNA (mtDNA) haplotype test showed that:Ⅱa haplotype strains andⅡb haplotypes accounted for 68.75%and 31.25%respectively, I a and I b haplotype was not found. Analysis on different periods of genetic diversity of P. infestans with SSR molecular markers, the results showed that the genetic diversity of advanced P. infestans was higher than earlier groups of P. infestans.Cluster analysis showed that:the strains of early and late cross-strain distribution in the different groups, indicated that SSR markers can not effectively distinguish between the different periods P. infestans populations.Analysis on the population genetic structure of the 60 P. infestans collected from different host plants in different parts of China with SSR molecular markers, the results showed that:the genetic diversity of tomato P. infestans population was higher than potato P. infestans populations. The genetic distance of Potato P. infestans population and Tomato P. infestans was 0.0250, indicated that the shorter differentiation. Cluster analysis showed that:potato and tomato P. infestans can not be completely divided into two different groups, but the cross-distribution in the different groups. Combined the results of the strain resistance to metalaxyl, mating type and mtDNA haplotype with the clustering analysis, the results showed that:there was not relationship between the genetic lineage and metalaxy resistance and mating type,but there was relationship between the genetic lineage and mtDNA haplotype.103 avirulence genes Avr3a of Phytophthora infestans Collected from different regions of China were sequenced. The polymorphism of sequences and the genetic diversity and expected number of haplotypes were detected with Clustalx and Dnasp5.10.0.1, the results showed that:The polymorphism of P. infestans avirulence gene Avr3a is due to the basic base substitution (transition, transversion Replacement), insertion and deletion. Major mutation occurred in the 109-117 nucleotide region, including the deletion and replacement; the genetic diversity of south P. infestans populations was higher than the north. P. infestans avirulence gene Avr3a follow the neutral evolution model. The least squares method(DSS) implemented in TOPALi v2.5 were used to detect intragenic recombination breakpoints, the results showed that:there was not intragenic recombination occurred. MEGA5 was used to construct phylogenetic tree, the results showed that:there was recent evolutionary relationship between the TianYang Guangxi Pinfestans TZ5,TZ7 and the standard strains Avr3a, followed by the remaining strains, there was the farthest evolutionary between the Heilongjiang Hegang Pinfestans W34 and the standard strains.