Introgression of germplasm from winter into spring Brassica napus: Detection and confirmation of quantitative trait loci

Introgression of winter germplasm into spring oilseed Brassica napus represents a novel approach to broaden the genetic base and potentially boost seed yields of spring hybrid cultivars. To determine the usefulness of this approach, two populations of segregating doubled haploid (DH) lines were developed by crossing the same spring-type parent to two lines having spring growth habit but with introgression of winter germplasm from two related French winter cultivars. These DH lines were evaluated per se and in testcrosses with a spring canola line used in commercial canola hybrids. Thirty percent of the hybrids significantly outperformed the commercial hybrids included in each trial. Many hybrids performed significantly better than the starting hybrid combination, especially in the Canadian environments.; To identify the introgressed genomic regions associated with seed yield and other traits, quantitative trait loci (QTL) mapping analyses were conducted in the DH lines and their testcrosses. From these analyses, six QTL were detected in the testcross populations for which the winter alleles increased seed yield. A QTL located in the linkage group N10, which explained 11% and 19% of the phenotypic variation in the testcross populations, was detected in the Canadian environments. A QTL for which the winter allele increased seed yield was linked to a canola quality QTL for which the winter allele increased glucosinolate content. This finding suggests that seed yield genes could be lost in the transformation of rapeseed into the canola commodity. It was found that most of the QTL for which the winter allele decreased seed yield in testcrosses were associated with genomic regions having chromosomal rearrangements, suggesting that these phenomena might play major role in the genetic control of complex traits, such as seed yield, in Brassica napus.; A QTL previously identified was confirmed through an approach that involved introduction of the putative QTL in multiple genetic backgrounds and evaluation in an appropriate experimental design. The results of this study illustrate how introgression of winter germplasms can improve seed yield in spring canola hybrids.