COMPARING THE RESYNTHESIS OF BRASSICA-NAPUS L BY INTERSPECIFIC SOMATIC AND SEXUAL HYBRIDIZATION .2. HYBRID MORPHOLOGY AND IDENTIFYING ORGANELLE GENOMES

Brassica napus (genome aacc), a natural allotetraploid derived from hy bridization between B. oleracea L. (genome cc) and B. rapa L. (genome aa), was resynthesized by somatic and sexual hybridization. Seventy-tw o interspecific somatic (R0) hybrids and 27 sexual (F1) hybrids were p roduced from the same parent plants. R0 and F1 hybrids displayed morph ology that was intermediate to the species parents, but B. rapa charac teristics tended to predominate. R0 hybrids with nuclear DNA content e quivalent to natural B. napus were uniform for nuclear-encoded traits, whereas allotetraploid F1 hybrids were variable for traits such as mo rphology, flower color, and seed production. Chloroplast restriction f ragment length polymorphisms (RFLPs) showed unequal segregation in the R0 population favoring the chloroplasts of B. rapa; two of the 58 R0 hybrids tested had only the B. oleracea marker and 10 contained marker s of both parents. Mitochondrial RFLPs showed a similar bias among the 56 R0 hybrids tested; only four plants showed B. oleracea markers exc lusively, and the remaining plants were evenly distributed between hav ing only B. rapa markers or having combinations from both species. In contrast, sexual hybrids displayed only maternal organelle markers.