QTL analysis of four yield-related traits for Brassica napus L. in multiple environments

Abstract

Yield improvement is an important target for rapeseed breeding. Resolving the genetic architecture of yield in Brassica napus, QTL analysis was carried out in a double haploid population derived from a cross between ZS11 and QU cultivars. A 60-K SNP chip was used to construct a genetic linkage map; a total of 5044 SNP markers were mapped to 19 linkage groups. QTLs of yield-related traits were mapped for seed density (SD), silique density on the main inflorescence (SDMI), thousand seed weight (TSW), and silique length (SL) in seven environments and 3 years experiments. Four major consensus QTLs of SD, TSW, and SL were identified in seven environments, explaining 48.06, 53.27, 37.13, and 52.13% of phenotypic variation, respectively. Two major consensus QTLs of SDMI were detected in six environments, explaining 13.32 and 11.76% of phenotypic variation, respectively. Notably, nine major consensus QTLs of SD, SDMI, TSW, and SL showed narrower confidence intervals (< 1 Mb). Moreover, two major pleiotropic QTLs controlling three traits (SD, TSW, and SL) simultaneously were identified, co-locating on 23.82–26.66 Mb, 27.06–28.53 Mb on chromosome A9 of B. napus, respectively. Most importantly, our research reveals the first (to our knowledge) pleiotropic QTLs, which controlled SD, TSW, and SL on chromosome A9 in B. napus. Furthermore, we found eight possible candidate genes might be related to SD, TSW, and SL, synchronously. Overall, these results lay a foundation for developing closely linked molecular markers, conducting fine mapping and gene cloning for yield-related traits in B. napus.