Mapping and identification of a new potential dominant resistance gene to turnip mosaic virus in Brassica rapa

Main conclusion By constructing an F-2 population, a new potential dominant resistance gene to TuMV in Brassica rapa was mapped and identified. Brassica rapa is the most widely grown vegetable crop in China, and turnip mosaic virus (TuMV) is a great threat to its production. Hence, it is a very important work to excavate more and novel resistance genes in B. rapa. In this study, the resistant line B80124 and the susceptible line B80450 were used to construct the F-2 populations, and through genetic analysis, the resistance to TuMV was found to be controlled by a dominant gene. Bulked segregant analysis sequence (BSA-seq) was used for the primary mapping, and an intersection (22.25-25.03 Mb) was obtained. After fine mapping using single nucleotide polymorphisms (SNP) markers, the candidate region was narrowed to 330 kb between the SNP markers A06S11 and A06S14, including eight genes relating to disease resistance. Using the transcriptome analysis and sequence identification, BraA06g035130.3C was screened as the final candidate gene, and it contained two deletion mutations, leading to frameshift in the susceptible line B80450. In addition, the phylogenetic analysis, hydrophilia and hydrophobicity analysis, subcellular location prediction analysis, amino acid bias analysis, and 3D modeling structures of BraA06g035130.3C were conducted to predict its functions. This study was conducive to the identification of a new TuMV resistance gene in B. rapa, which is of important scientific significance and application value for the improvement of TuMV resistance traits and molecular design breeding for Brassica crops.