To cite this paper: Tantasawat, P.A., A. Sorntip, O. Poolsawat, W. Chaowiset and P. Pornbungkerd, 2015. Evaluation of factors affecting embryo-like structure and callus formation in unpollinated ovary culture of cucumber (Cucumis sativus AbstractThe 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 (GA 3 ) 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.

The effects of exogenous application of plant growth regulators (PGRs) were evaluated on both field performance and in vitro gynogenesis of ‘Chai Lai’ and ‘Big C’ cucumber (Cucumis sativus L.). Plants were sprayed with two concentrations of N6-furfuryladenine [kinetin (KIN); 2 and 20 ppm], 2,3,5-triiodobenzoic acid (TIBA; 1 and 10 ppm), naphthaleneacetic acid (NAA; 10 and 100 ppm), abscisic acid (ABA; 2 and 20 ppm), thidiazuron (TDZ; 1 and 10 ppm), and maleic hydrazide (MH; 10 and 100 ppm) to assess their effects on vegetative growth and floral and yield related traits in the Winter of 2013 and in the Summer of 2014 compared with distilled water control. Meanwhile, the effects of two PGRs (KIN and TIBA) on cucumber gynogenesis were also investigated in vitro. Growth parameters and floral and yield-related traits were significantly affected by the various PGRs in both cultivars during both seasons. In both cultivars, the highest yield was obtained with the application of 10 ppm NAA during the Winter of 2013 (1.5- to 1.8-fold over control) and with 1 ppm TIBA during the Summer of 2014 (2.1- to 2.2-fold over control). With regard to the ovary culture response, exogenous application of KIN and TIBA on floral buds tended to enhance callus formation in ‘Chai Lai’ cultured on I7 medium, whereas no effect was observed in ‘Big C’. The embryo-like structure (ELS) formation efficiencies also tended to increase with 2 and 20 ppm KIN and 1 ppm TIBA application in ‘Chai Lai’ and with 20 ppm KIN and 1 ppm TIBA application in ‘Big C’ when cultured on I7 medium. Nevertheless, TIBA at high concentrations (10 ppm) decreased the percentages of ELS formation and the number of ELSs/piece in both cultivars. These results suggest that the polar auxin transport may play a major role on growth, floral and yield-related traits, yield as well as in vitro gynogenesis in cucumber. However, the success of exogenous applications of these PGRs depended on several factors including plant genotypes, growing seasons, types and concentrations of PGRs, and for ovary culture, the responses also varied according to the induction media used. Chemical names: abscisic acid (ABA); maleic hydrazide (MH); naphthaleneacetic acid (NAA); N6-furfuryladenine (kinetin; KIN); thidiazuron (TDZ); 2,3,5-triiodobenzoic acid (TIBA).

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Gynogenesis and doubled haploid production from unpollinated ovary culture of cucumber (Cucumis sativus L.

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