Branch number(BN)is an important yield-related trait controlled by quantitative trait loci(QTL)in oilseed rape(Brassica napus L.).The genetic bases underlying this trait is largely unknown at present.In order to identify the genes for branch number in oilseed rape,we conducted QTL analyses for BN using 184 F2:3 families derived from a cross between MB01,an inbred line with extremely much primary branches,and 0830112,an inbred line with normal number of primary branches.The F2:3 population were grown in Wuhan in the 2009/10 growing season,and mean BN for each family were investigated.A complete linkage map of F2 population was constructed using 197 marker loci.Five QTL were identified for BN.Of these,a major QTL,qBNA6.1,explained as much as 24.4%of BN variation,and the MB01 allele at this locus increases BN.The other four are minor QTL and individually explained less than 20%of the BN variation.The stability and significance of qBNA6.1 were further validated in the RIL population derived from the same cross.The results in this study revealed that the number of primary branch in the MB01 inbred line was sizable controlled by the qBNA6.1 locus,which was suitable for fine mapping and marker-assisted selection in rapeseed breeding for high yield.