Mapping of quantitative trait loci related to cold resistance in Brassica napus L.

ABSTRACT

Cold stress is one of the major abiotic stresses that seriously limit rapeseed production worldwide. However, few studies on the mechanism of cold resistance in Brassica napus have been reported. In this study, an F23 population including 147 lines was developed to identify the quantitative trait loci (QTLs) related to cold resistance in B. napus. As a result, a genetic linkage map based on 333 simple sequence repeat (SSR) markers covering 1317.70 cM was constructed. Up to 11 QTLs for four indicators were identified in the two locations. These QTLs accounted for 1.09% to 42.50% of the phenotypic variations, and six major QTLs accounted for more than 10% of the phenotypic variations. Three QTLs, qSPADYL-6, qSPADYS-6, and qMDAYS-6, were mapped to the same region of linkage group 6 (LG6). Blast analysis indicated that the sequences of the markers related to these three QTLs showed great collinearity with those on the A08 chromosome of Brassica rapa, and that the target genes might exist in the region from 1.069 to 15.652 M on A08. Two genes, BnaA08g05330D and BnaA08g15470D, encoding the respective cold-regulated proteins in B. napus, were identified. They exhibited high similarity with Bra039858 and Bra010579 (stress-responsive proteins) in the candidate region. RT-qPCR analysis showed a significant difference in gene expression between the two parents. These two genes were hence identified as the genes responsible for cold resistance.