Abstract:

Since yield traits are complicated quantitative traits, QTLs mapping and genetic effects analyzed for seed yield and its components can help us to understand the source for heterosis and improve the selecting efficiency for good genotype of seed yield. A genetic linkage map consisting of 244 DNA markers was constructed based on F₂ population derived from a cross between double low parent CMS maintainer 1141B and double high CMS restorer KenC1. The markers in the linkage map distributed on all the 20 main linkage groups and 1 triplet and covered 2 769.5 cM of the rapeseed genome. The statistic software of Windows QTL Cartographer Version2.0 and Composite Internal Mapping (CIM) were applied to detect QTLs for seed yield and its components, including seed yield per plant, number of silique per plant, number of seed per silique and 1000-seed weight. A total of 16 QTLs located in nine different linkage groups were identified for seed yield and the three component traits. There were three QTLs (the most QTLs) in LG6 and LG13, respectively. Each of these QTLs explained 0.38%–73.34% of the phenotypic variance. They had additional effect of alleles that came from maternal parent, the others from paternal parent for the same trait. Epistatic effect was screened in all 20 linkage groups using all possible loci pairs by two-way ANOVAs between co-dominant markers. Twenty-six two-locus combinations had significant epistatic effects. The results showed that there were many interaction loci involving the entire genome detected in yield traits. The epistatic interactions had pleiotropic effects, interactions were contained epistasis between QTL and non-QTL (non-significant effect loci) and between non-QTL. The later was the majority. In general, the independent effect of interaction loci was lower, on the opposite, the value of interaction effect was higher, and much higher than the total of independent effects.This indicated that the genes controlling seed yield was complicated. Epistasis interactions might play an important role as the basis of heterosis in Brassica napus L. Some questions about QTLs mapping were also discussed.

Key words: Brassica napus L., Yield components, Genetic linkage map, Molecular marker, QTL mapping, Epistatic effect