Phenotypic effects of introgressing Chinese winter and resynthesized Brassica napus L. germplasm into hybrid spring canola

The seed yields of hybrid spring canola (Brassica napus L.) could be improved by introducing favorable alleles from unadapted germplasm. Two sources of unadapted germplasm, a Chinese winter cultivar, Hua-db12, and a resynthesized R napus line derived from a cross between B. rapa cv. Reward and rapid cycling B. oleracea L., were crossed to the male parent of a hybrid combination. From both crosses, a segregating population of doubled haploid (DH) lines was created by microspore culture. DH lines were evaluated per se (2 yr in Wisconsin, USA) and in testcrosses to the female parent of the hybrid combination (2 yr in Wisconsin, USA, and 1 or 2 yr in Saskatchewan, Canada). Many of the testcrosses had significantly higher seed yields than the starting hybrid combination in both the Wisconsin and Saskatchewan environments. Some of the testcross lines had significantly higher seed yields than all of the commercial hybrid checks included in the trial. These results indicate that the seed yield of spring canola hybrids may be improved through introgression of novel alleles residing within these unadapted germplasms. The populations developed for this study can be used to map loci for which alleles from the unadapted parent increase seed yield of spring canola hybrids.