Genetic Analysis And QTL Mapping Of Yield-Related Traits In Cabbage

Cabbage is one of the most widely cultivated vegetables around the world.Most of the commercial varieties are hybrids due to the fact that cabbage has obvious heterosis.In this study,a DH population was used as material to construct a high-density genetic linkage map for cabbage with genotyping by sequencing(GBS)technology.Genetic analysis and QTL mapping were performed on head-yield-related traits and their general combining ability,mid-parent heterosis and transgressive heterosis.Then important chromosome loci or regions were found and these results will provide basis for molecular marker-assisted breeding of cabbage.The main results are as follows:1.A high-density genetic linkage map of cabbage was constructed by DH population.The elite parents 01-20 and 96-100 were re-sequenced at about 16 × depth of coverage.A total of 2,450,757 SNPs between two parents were obtained.100 DH lines were re-sequenced at about 2 × depth of coverage and694,883 SNP markers were developed in the DH population.Then 1465 bin markers were obtained by sliding window and a high-density genetic linkage map of cabbage was further constructed.The average genetic distance between two adjacent bin markers was 0.88 cM.2.Phenotypic investigation of head yield-related traits in DH population was conducted in two years.A total of 52 QTLs associated with head-yield related traits were detected,of which 53.8% could be detected repeatedly.Seven QTL clusters were detected,and three of them were on chromosome C03.QTL cluster mk303-321 on chromosome C03 contained eight QTLs,controlling seven head yield-related agronomic traits.3.The 100 DH lines were crossed with two parents N12 and N16 to obtain the tested cross populations.QTLs for the general combining ability of 12 head yield-related traits were identified and forty QTLs were obtained.QTL loci qGHvd2 was identified three times for controlling general combining ability of cabbage head vertical diameter.It was located in mk149-158 on chromosome C02 and contribution rate was 27%.4.Elite parent 01-20 contained two important chromosome regions mk300-316 and mk258-268 contributing to high heterosis.When N12 was used as the tester,38 mid-parent heterosis QTL loci and41 transgressive heterosis QTL loci were detected.When N16 was used as the tester,28 mid-parent heterosis QTL loci and 32 transgressive heterosis QTL loci were detected.Mk300-316 was one important chromosome region to control heterosis of biological yield,it contained an important mid-parental heterosis QTL loci qMBy3.1 with a contribution rate of 18.3% and an important transgressive heterosis QTL loci qTBy3.1 which was detected in two testcross populations.Mk258-268 was another important chromosome region controlling heterosis of economic yield,it contained an important transgressive heterosis QTL loci qTEy1 with a contribution rate of 19.5%,and an important mid-parental heterosis QTL loci qMEy2 with a contribution rate of 17.1%.