| Chinese cabbage is a Brassica plant that originated in China.It is the largest vegetable crop planted in China.It has great edible and nutritional value in people's lives.Cruciferous clubroot disease caused by Plasmodiophora brasicae Woronin is a worldwide soil-borne disease that causes fatal damage to various cruciferous crops and is one of the important diseases of brassica crops in the world.The disease spreads rapidly and currently poses a serious threat to the production of various vegetables,especially the quality and yield of Chinese cabbage.With the increase of Chinese cabbage planting area,the damage of clubroot disease is getting more and more serious.It is the most effective and direct solution to clubroot disease to find new resistance genes and to develop new disease resistance varieties.After several years of inoculation and identification,CR026 is a Chinese cabbage variety with very good resistance to clubroot disease.In order to clarify its disease resistance genes and develop linkage markers,In this study,high-sensitivity Chinese cabbage inbreds 17A12 and CR026 were used to obtain F1,and F2 was used to obtain F2.The F2 generation was identified for inoculation.select 20 extremely disease-resistant single plants,20 extremely susceptible individual plants,and use BSA(separated population grouping analysis)method to establish resistance pools and susceptible pools to the existing laboratory SSR,Indel,and SNP markers were screened with the developed 653,and 180 F2 were then selfed with 180 F2: 3 families.After molecular markers and inoculation phenotypic verification,they were finally closely linked with resistance to rhizoma Molecular markers and preliminary mapping of anti-disease genes.The following results were obtained:For 72 F1 generations were inoculated and identified.It was found that the F1 generation was susceptible,and then F2 was obtained through F1 selfing.Using BSA resequencing,it was found that there are obvious differences on A01 and A08 chromosomes.Then 179 F2: 3 families were inoculated,and the ratio of disease resistance and susceptibility of F2 was verified by the inoculation results.R: S = 12: 167,Chi-square test ?2 = 0.062 <5.99 meets the separation ratio of 1:15.Therefore,it is inferred that the resistance to root swelling disease is controlled by two genes.The site on the A01 chromosome is temporarily named Bra A.PB.1.2,and the site on the A08 chromosome is named Bra A.Pb.8.2.Molecular markers were performed on 179 F2: 3 families.By screening 653 pairs of primers,there were 113 pairs of polymorphic primers,including 17 pairs on A01,20 pairs on A08,and 6 SSR markers on A01.Linked to disease resistance genes,the upstream are C230,C228 and C141,and the downstream are ACMP473,C234 and ACMP334,respectively.The two closest flanking markers are C230 and ACMP473 with a genetic distance of 4.9 c M and a physical distance of 0.44 Mb.There are two SSR markers and three SNP markers linked to the disease resistance gene on A08.The upstream are C044 and C353,and the downstream are A08-107,A08-108,and A08-106.The genetic distance between the two closest flanking markers is 11.8c M and the physical distance is 2.09 Mb.The combined analysis of the genotype and phenotype of the F2: 3 family found that when both genes were homozygous,the plant showed absolute disease resistance;when Bra A.PB.1.2 was homozygous and Bra A.Pb.8.2 was heterozygous or Bra A.PB.1.2 is heterozygous.Bra A.Pb.8.2 is poorly resistant when homozygous,and completely susceptible when two genotypes are heterozygous or susceptible.Two genes are inherited independently.Genetic analysis has shown that each gene itself has little effect on resistance to rhizoma,but the two genes are complementary.After verification of the genotype and phenotype of 85 F2 disease-resistant plants and 96 susceptible plants,the results were consistent with the above,so it was proved that the two genes are recessive homozygous disease resistance genes,and they are functionally complementary and independent inheritance.Two disease resistance genes.In summary,in this study,by constructing the F2 population,we further obtained F2: 3 families,and inoculated with Korean KEL23 rhizobium to complete the preliminary mapping and development of the gene against rhizoma in CR026 And verified the molecular markers closely linked with Bra A.PB.1.2,Bra A.Pb.8.2 genes,these markers can be applied to the selection of Chinese cabbage resistance to clubroot disease,providing a new source of resistance for further research The molecular function of disease genes lays the foundation. |
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