Abstract：Kale (Brassica oleracea var. acephala) belongs to the Brassica genus of Cruciferea. Ornamental kale has colorful leaves under cold temperature, and is a good all-purpose plant material from late autumn to early spring due to its beautiful and long lasting foliage and edible traits. As the strong heterosis, the commodity is basically an F1 hybrid. Based on the years of work with the double haploid breeding of ornamental kale, this study summarized our achievements in double haploid (DH) plant production via microspore culture and its application in breeding. The materials used included the round leaf types (cabbage type), the curly leaf type, and the feathered leaf type. Microspore donor plants were 103 different genotypes, which came from commercial varieties, F2~F3 selfed progenies, and new hybrid combinations. Microspore embryoids and derived plants were obtained from 77.7% and 55.3% of the 103 genotypes, respectively. The average number of embryoids per petri dish (3×105 microspores) varied from 0 to 314, and much higher number of embryoids were formed from donor plant hybridized between DH lines. Non synchronous developments of the embryoids were observed in general, and the plant formation frequencies varied from 0 to 51.3%. F1 hybrids owned significant higher embryogenesis capacity than progenies of themselves, but plants possessing of relatively higher embryoid formation capacity in F2 ~F3 population also existed. There were haploidy, diploidy, triploidy, tetraploidy and mixed-ploidy in the regenerated plants, and the frequency of doubled haploid (DH) in average was about 42.7%. The phenotype diversities were rich in DHs derived from F1 hybrids, while the diversities were relatively low in DHs derived from the F3 donor plants. Multi-traits, such as leaf color, blade profile, plant type, etc., were rapidly fixed and multilevel displayed in the DHs, also the recessive gene controlling traits were contemporary expressed. Compared with the conventional breeding, more than half of the time could be saved using DH breeding system for a new F1 hybrid release in ornamental kale. This research provides a relative complete reference for double haploid breeding not only for kale but also for other crops.
