Identification of Clubroot () Resistance Loci in Chinese Cabbage ( ssp. ) with Recessive Character.

The soil-borne pathogen is the causal agent of clubroot, a major disease in Chinese cabbage ( ssp. ). The host's resistance genes often confer immunity to only specific pathotypes and may be rapidly overcome. Identification of novel clubroot resistance (CR) from germplasm sources is necessary. In this study, Bap246 was tested by being crossed with different highly susceptible materials and showed recessive resistance to clubroot. An F population derived from Bap246 × Bac1344 was used to locate the resistance Quantitative Trait Loci (QTL) by Bulk Segregant Analysis Sequencing (BSA-Seq) and QTL mapping methods. Two QTL on chromosomes A01 (4.67-6.06 Mb) and A08 (10.42-11.43 Mb) were found and named and , respectively. Fifteen and eleven SNP/InDel markers were used to narrow the target regions in the larger F population to 4.67-5.17 Mb (A01) and 10.70-10.84 Mb (A08), with 85 and 19 candidate genes, respectively. The phenotypic variation explained (PVE) of the two QTL were 30.97% and 8.65%, respectively. Combined with gene annotation, mutation site analysis, and real-time quantitative polymerase chain reaction (qRT-PCR) analysis, one candidate gene in A08 was identified, namely . And an insertion and deletion (InDel) marker (co-segregated) named Crr1-196 was developed based on the gene sequence. , , , , , and in A01 were the candidate genes that may confer clubroot resistance in Chinese cabbage. The resistance resource and the developed marker will be helpful in breeding programs.