Identification of QTLs for Seed Yield and Yield-Related Traits in Brassica Napus Grown with Contrasting Nitrogen Supplies

Abstract

\n Oilseed rape (Brassica napus L.; B. napus) is the main oil crop in China as well as in the world. Nitrogen (N) deficiency significantly reduces the seed yield of B. napus. However, a very few studies involved in the genetic mechanism of seed yield (SY) and SY-related traits of B. napus in response to N deficiency. In this study, plant height (PH), branch number (BN), pod number (PN), seed number (SN), 1000-seed weight (SW) and SY were investigated using a B. napus double haploid (BnaTNDH) population derived from a cross between cultivars ‘Tapidor’ and ‘Ningyou7’ grown at an optimal (ON) and a low N (LN) supplies in three-year field trials. Great variations of SY and related traits were observed in BnaTNDH population under contrasting N supplies. A total of 106 and 110 significant quantitative trait loci (QTLs) were detected for six traits at ON and LN in three field trials, respectively. All of these significant QTLs for the same trait were integrated into 191 consensus QTLs. Nine and eleven consensus QTLs at ON and LN were detected in two or three trials, respectively, and the remaining were environment-specific. One hundred and three unique QTLs were integrated from 191 consensus QTLs, including 29 low N specific QTLs, 35 optimal N specific QTLs and 39 constitutive QTLs. uqA3q was integrated from four consensus QTLs for PN, PH, SN, SY at LN, uqC9f was integrated from consensus QTLs for BN, SY, PN at ON and LN. Both were detected in three trials. This result may help to better understand the genetic mechanism of yield traits in response to low N and promote the breeding of N efficient varieties.