Evaluation of Factors Affecting Embryo-like Structure and Callus Formation in Unpollinated Ovary Culture of Cucumber (Cucumis sativus)

Abstract

The effects of various factors including genotypes of donor plants, induction and differentiation media, and thermal shock pretreatment were evaluated on embryo-like structure (ELS) and callus formation in an unpollinated ovary culture of cucumber. All five cucumber cultivars, which were used as donor plants, produced ELSs and calli, although their ELS and callus formation potentials varied significantly. The addition of 1 mg/L thidiazuron (TDZ) and 1 mg/L 6-benzylaminopurine (BA) into the induction medium resulted in the highest percentage of ELS formation, ranging from 42.3 to 91.4% with an average of 60.4%. However, the highest percentage of callus formation was observed in an induction medium containing 2 mg/L BA, 0.5 mg/L indole-3-acetic acid (IAA), 1 mg/L gibberellic acid (GA3) and 32 mg/L putrescine (70.8%). By contrast, differentiation media had no significant effect on the formation potentials of both ELSs and calli. Thermal shock pretreatment reduced the percentage of ELS formation ca. 1.3-fold, but had no significant effect on callus formation. These results can be implicated for the efficient production of cucumber doubled haploids in the future.