Mapping Of Clubroot Resistance Gene BrA.Pb8.3 In Chinese Cabbage

Chinese cabbage is one of the Brassica vegetable crops and is an important vegetable crop in China.However,in recent years,due to the accelerated spread of rhizome disease,it has become a major disease in the production of cruciferous vegetable crops,which seriously affects its yield and quality.Plasmodiophora brassicae is parasitic on cruciferous plants and causes abnormal swelling of the root.Clubroot disease is a worldwide parasitic soil-borne disease caused by obstetric infection of Plasmodiophora brassicae?Ludwig Muller J et al.,1999?.The rapid spread of Plasmodiophora brassicae with agricultural operations,flowing water and other methods,and the long survival time of dormant spores in the soil are the main reasons to control.clubroot disease.In this study,the Chinese cabbage resistance material 377 and the highly susceptible disease material 12 A were used as parents to construct an F₂ population after selfing,and the phenotypic identification of radicle disease was performed after inoculation.Based on the phenotypic identification results of the F₂ population,the genetic laws of the resistance material of the test were analyzed.By constructing a pool of resistant plants and screening by SSR markers,a genetic map and a physical map were constructed.The disease genes were initially mapped.The experimental results are as follows:1.F1,obtained by crossing the resistant parent material '377' with the susceptible material '12A',showed resistance to disease after inoculation.470 individual plants of the self-bred progeny F₂ population were identified by inoculation of rhizobium and obtained according to the classification standard.The results were 357 disease-resistant plants and 113 susceptible plants.The chi-square test showed no significant difference between the actual value and the theoretical value,which was in accordance with the Mendelian genetic separation ratio of 3: 1?X² = 0.18 <X²0.05 = 3.84?.This shows that the resistance of the material to clubroot disease is mainly controlled by a dominant major gene,that is,the resistance of the Chinese cabbage resistance material to the clubroot resistance '377' is controlled by a dominant single gene.2.In this study,mixed pools were constructed based on the extreme phenotypes of plants in the F₂ generation population,that is,disease-resistant grades 0 and 3 were selected for BSA sequencing,and 10 pairs of SSR markers with polymorphism were used for resistance Gene mapping.The physical map and genetic map were constructed using Join Map4.0 software and Mapchart.Finally,the disease resistance sites were identified on the eighth chromosome markers sau6127 and Acmp08-2 of Chinese cabbage,named 'Br A.Pb8.3'.Six pairs of primers designed near and within the interval between markers sau6127 and Acmp08-2 were used to perform genotype verification on the recombinants obtained.The identification results were analyzed and the resistance gene in the root disease resistance material '377' was finally analyzedis located on chromosome 8 of Chinese cabbage chromosome,located between markers sau6127 and Acmp08-2.The genetic distance of the closest marker to the disease resistance gene is 0.6cM.