Fine Mapping Of Clubroot-resistance Gene CR₂₀₅ In Chinese Cabbage

Chinese cabbage clubroot is a kind of soil-brone disease.It is a highly contagious caused by the infection of Plasmodiophora brassica.It can cause the yield droping or losting for Chinese cabbage.In this experiment,we used BSA-Seq,SSR and In Del molecular marker technology to locate the resistance genes to P.brassica of Chinese cabbage.The results are as follows:1.At first,F₂population was obtained by hybridization of the resistant variety‘205'and the susceptible variety‘157',and the P.brassica inoculation method was improved by adjusting the microbial concentration and improving the plant culture method.Then the hereditary law was investigated by inoculating with P.brassica to resistant or susceptible varieties and F₂isolated population and positive and negative combinations.Finally,we found the segregation ratiol of resistance plants to susceptible plants of F₂isolated population is about 3:1,which was in agreement with Mendel's law of segregation.It was proved that the disease resistance of this test material is controlled by a pair of dominant nuclear genes.2.According to the BSA-Seq sequencing requirements,the parents and the F₂isolated population was selected according resistant phenotype,and then it was established that the mixed pools of every parents and two extreme mixed pools of F₂separated population.The parents are the 10X sequencing depth and the F₂isolated population is the 30X sequencing depth.Through BSA-Seq sequencing analysis,the target gene was initially located on A03chromosome.3.SSR and indel primers were designed for a unit of 50kbp interval according to the results of BSA-Seq.After the target area was locked,the primers were designed for a unit of20kbp interval.Finally,two markers,Bra-CR-123 and Bra-CR-125,with a genetic distance of0.25c M,were obtained.Between the two markers,there was a gene Bra A03g055010.3c,which contains leucine rich repeat sequence and can encode the N-terminal gene of protein,so the target gene is finally located on Bra A03g055010.3C gene within version 3.0 of Chinese cabbage database,called CR₂₀₅.