| Anther culture has not yet been widely used to generate new cultivars in winter rapeseed breeding programs. The first objectives of this study were to assess rapeseed genotypes from the Colorado State University breeding program for their regenerative ability in anther culture and optimize the environmental conditions for anther culture of breeding lines. Anthers of four cultivars of rapeseed--Westar, Pivot, Cascade, and Bridger--and four breeding lines from crosses of Westar x Bridger, Westar x Pivot, Bridger x Pivot, and Westar x Bridger were placed in culture and observed for embryo formation. Environmental effects of anther culture medium, days of incubation at 35{dollar}spcirc{dollar}C, and anther donor plant growth conditions on the resulting embryo production also were defined. Only two breeding lines (Westar x Bridger and Bridger x Pivot) produced embryos in anther culture, and genotype was a significant factor in embryo formation. Up to 32 percent of the anthers from the Westar x Bridger line and 2.38 percent of the anthers from the Bridger x Pivot line produced embryos. Significant differences in embryo formation also were observed due to days of incubation at 35{dollar}spcirc{dollar}C and anther donor plant growing conditions. The highest proportion of anthers producing embryoids resulted from anthers of the greenhouse-grown Westar x Bridger line after 21 days of incubation at 35{dollar}spcirc{dollar}C.; After obtaining regenerants, the next set of objectives in this study was to confirm haploid origin of regenerants and determine if selection occurs during anther culture. Haploid origin and allelic segregation ratios were investigated by using isozyme electrophoresis. Analysis of the diaphorase locus isozymes revealed a haploid origin of regenerants, existence of in vitro selection during anther culture, and linkage between diaphorase and regeneration capacity genes. Thus anther culture can be used to generate haploids for a breeding program of winter rapeseed, but haploid generation may be limited by genotypic and environmental factors, and selection may occur during the anther culture process. |
