The Study Of Plasmodiophora Brassicae Genetic Diversity

Currently,Brassicaceae clubroot is spread all over the world.The clubroot desease do harm to the production of cruciferous crops,many plants can be affect.The pathogen of clubroot is Plasmodiophora brassicae Woronin.It is an obligate parasite in cruciferous crops root cells.Plasmodiophora brassicae infect and grow in their hosts by root hair infection.Then it can cause the abnormal proliferation of host roots and result in tumor formation.However,Plasmodiophora brassicae has a high degree of genetic differentiation and variation,which brings difficulties to desease control and plants resistance breeding.In this study,we using the Williams system at first to identify the races of 36 clubroot materials which collected from different areas in China and one of them in South Korea.Then we download the whole genome sequence of Plasmodiophora brassicae in NCBI public database.Searching SSRs on the genome by SSRHunter software.Next we using SSR molecular marker technology to develop and screen plasmodiophora brassicae genomic SSR primers through 40 clubroot materials.After obtain the SSR result data,we clustering analysis and the genetic diversity of Plasmodiophora brassicae revealed.The main results of are as follows:1.Using Williams identification system on 36 clubroot materials,which collect from China infect areas including Yunnan,Sichuan,Chongqing,Anhui,Liaoning,Hubei,Shanxi,Jiangsu province and South Korea,to identify different physiological races.Results show that the main pathogen of plasmodiophora brassicae is race 4.This result is consistent with previous researches.In addition,2,4,7,11 physiological races were also identified.2.Searching the SSR sequence of Plasmodiophora brassicae genome.The results showed that there are 3174 SSRs in Plasmodiophora brassicae genome,and the average distance between SSR was 7.58 kb.Dinucleotide and trinucleotide repeats are the main types of SSRs,accounting for 98.99%.Most SSRs are trinucleotide repeats,accounting for 52.84% in all SSRs.There is a relatively small number of tetranucleotide,pentanucleotide and hexanucleotide repeats.There are 30 kinds of motif repeat type in the genome of Plasmodiophora brassicae.The ACG/CGT trinucleotide repeat motifs are the most frequent motifs,accounting for 25.11% of total SSR.AC/GT and GC/CG are the main dinucleotide repeat motifs,accounting for 21.11% and 20.29%.3.We design and synthesize 62 pairs of primers.Then we analyze the SSR polymorphism of 40 clubroot materials from different provinces and regions.There are 32 pairs of primers show significant genetic polymorphisms in 40 kinds of strains DNA,and 97 allelic bands were amplified.4.Clustering analysis by software MEGA5.0,and then obtain the phylogenetic map of 40 strains.From the clustering tree,we can find that the genetic differentiation of Plasmodiophora brassicae physiological races is closely correlated with their geographical origins.40 test strains from different regions are divided into four clusters.Most of the strains collected from Yunnan and Chongqing are in the first cluster.Strains from Sichuan Province,Hubei Province,Shaanxi province and South Korea are mostly in the second cluster.While the strains collected from Anhui,Liaoning and Jiangsu province are all in the fourth cluster.