Microspore culture of white cabbage, Brassica oleracea var. capitata L.: Genetic improvement of non-responsive cultivars and effect of genome doubling agents

For the efficient application of haploid induction procedures in cabbage br eeding, a sufficient number of regenerants should be achieved in a broad sp ectrum of genotypes. However, the majority of genotypes are somewhat recalc itrant. The efficiency of microspore culture was tested by crossing a respo nsive (28.7 embryos per Petri dish) and a nonresponsive (0.1 embryo) cabbag e cultivar. The embryo yield of one progeny was intermediate (18.9) while t wo were superior to the best parent cultivar (52.9 and 64.0 embryos). Thus, genes for haploid embryogenesis, present in responsive lines, can be effec tively transmitted to responsive x non-responsive hybrids. Abscisic acid-in duced desiccation of embryos was used for the efficient regeneration of pla nts. High germination percentages (54.7-70.6%) followed by normal plantlet development were achieved. Spontaneous genome doubling measured at the plan tlet stage differed markedly in untreated genotypes. The percentage of dipl oids ranged from 21 to 67%. The effects of two antimitotic drugs applied to freshly isolated microspores were determined in two experiments. In the fi rst experiment, trifluralin (0.5 and 1.0 mg/l) had no effect on embryo indu ction while oryzalin partly (0.125-0.25 mg/l) or completely (0.5 mg/l) inhi bited the formation of embryos. In the second experiment, higher concentrat ions of trifluralin increased the proportion of diploidized plants. Applica tion of antimitotic drugs to microspores did generally not improve the over all production of haploid plants, which was higher in an untreated control.