Highly regenerative cultivars in microspore culture in Brassica oleracea L-var. capitata

Cabbage (Brassica oleracea L. var. capitata) has been reported to show a lo wer regenerative ability in microspore culture than broccoli (B. oleracea v ar, italica) or some other Brassica crops. Since the genotype is considered to be the most important factor affecting the embryogenesis of Brassica sp ecies, varietal differences in embryogenic and plant regenerative abilities from isolated microspores of cabbage accessions were examined to identify more responsive genotypes. Significant differences (<1%) were observed amon g the accessions in both the total number of embryos per 1 x 10(5) microspo res (embryo yield) and regenerative embryo yield. 'Matsunami', an Fl hybrid cultivar, showed the highest embryo yield and the highest efficiency of pl ant regeneration from microspores among the 38 accessions examined. The emb ryogenic ability of this cultivar was five to ten times higher than that pr eviously reported for other cabbage cultivars. Although 'M05', a breeding l ine, showed the second highest embryo yield, the plant regeneration ability was found to be very low. Embryos of 'M05' often developed abnormally and produced calli. No correlation was observed between the total embryo yield and the percentage of regenerative embryos among all the accessions studied and in the accessions without abnormal embryogenesis. These findings sugge st that plant regeneration from the embryo is controlled by genetic factors other than those controlling the embryogenesis itself, Forty doubled haplo id (DH) lines derived from microspores of 'Matsunami' were examined for eff iciency in embryo yield. Significant differences (<1%) in total embryo yiel d were observed among these DH lines. Though most of the DH lines showed a lower embryo yield than 'Matsunami' itself, four lines showed a higher yiel d than 'Matsunami'. These four DH lines are considered to be suitable for u se in the haploid method of breeding in cabbage.