Allelic variation of a clubroot resistance gene () in Japanese cultivars of Chinese cabbage ( L.).

Clubroot resistance (CR) is an important trait in Chinese cabbage breeding worldwide. Although , the gene responsible for clubroot-resistance, has been cloned and shown to encode the NLR protein, its allelic variation and molecular function remain unknown. Here, we investigated the sequence variation and function of three alleles cloned from six CR F cultivars of Chinese cabbage. Gain-of-function analysis revealed that isolated from the cv. 'Kinami 90' conferred clubroot resistance as observed for . Because two susceptible alleles commonly lacked 172 amino acids in the C-terminal region, we investigated clubroot resistance in transgenic Arabidopsis harboring the chimeric , in which 172 amino acids of the functional alleles were fused to the susceptible alleles. The fusion of the C-terminal region to the susceptible alleles restored resistance, indicating that their susceptibility was caused by the lack of the C-terminus. We developed DNA markers to detect the two functional alleles, and demonstrated that the functional alleles were frequently found in European fodder turnips, whereas they were rarely introduced into Japanese CR cultivars of Chinese cabbage. These results would contribute to CR breeding via marker-assisted selection and help our understanding of the molecular mechanisms underlying clubroot resistance.