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

Cabbage (Brassica oleracea L. var. capitata) has been reported to show a lower regenerative ability in microspore culture than broccoli (B. oleracea var, italica) or some other Brassica crops. Since the genotype is considered to be the most important factor affecting the embryogenesis of Brassica species, 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 among the accessions in both the total number of embryos per 1 x 10(5) microspores (embryo yield) and regenerative embryo yield. 'Matsunami', an Fl hybrid cultivar, showed the highest embryo yield and the highest efficiency of plant regeneration from microspores among the 38 accessions examined. The embryogenic ability of this cultivar was five to ten times higher than that previously reported for other cabbage cultivars. Although 'M05', a breeding line, 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 suggest that plant regeneration from the embryo is controlled by genetic factors other than those controlling the embryogenesis itself, Forty doubled haploid (DH) lines derived from microspores of 'Matsunami' were examined for efficiency in embryo yield. Significant differences (<1%) in total embryo yield 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 yield than 'Matsunami'. These four DH lines are considered to be suitable for use in the haploid method of breeding in cabbage.