Preliminary studies on the high frequency of double haploid in the ovary culture of cucumber

The rapid acquisition of double haploid plants has good application prospects in vegetable crop breeding, and it can shorten the breeding cycle. There have been some research findings of obtaining haploid plants by cucumber ovary culture, but the efficiency of obtaining haploid plants under natural conditions was low and it could normally not be set to retain its offspring. The aim of this study was to obtain the double haploid plants directly from the ovary culture of cucumber, while increasing the doubling rate of haploid plants and acquiring double haploid progeny of cucumber rapidly. In this research, we used the seven F-1 hybrid combinations of cucumber: CK, 12101, A-5, A-13, A-7, A-11, A-3, from which unpollinated ovaries two days before flowering were cultured in the modified B5 medium with 0, 10, 20, 30, 40, 50 mg L-1 gradient concentration of colchicine. The induction of callus, chromosome doubling, and regeneration of plants were simultaneously carried out, and the ploidy of the regeneration plants was identified by flow cytometry. The results showed that seven hybrid combinations could induce callus and the callus induction rate of A-3 was as high as 20.19%. Only A-3 and A-11 could regenerate the plants successfully. The plant regeneration rate of A-3 was 10.47% and the rate of the double haploid plant in the regeneration plant was 55.56%. The plant regeneration rate of A-11 was 16.67% and the rate of the double haploid plant in the regeneration plant was 69.23%. By comparing the relationships between the doubling rate and the concentration of colchicine, we found that 30 mg L-1 was the optimal concentration of colchicine to obtain the double haploid plants of cucumber while exceeding 30 mg L-1 would be the lethal efficiency.