Abstract

The aim of this work was to study the influence of various factors (sucrose concentration, silver nitrate, activated charcoal, and plant growth regulators 2.4-D (2.4-Dichlorophenoxyacetic Acid) and TDZ (Thidiazuron)) on the induction of gynogenesis and their effect on eight genotypes of summer squash on the ploidy level of regenerated summer squash plants (Cucurbita pepo L.) in isolated ovule culture in vitro. IMC (Induction Medium for Cucurbitaceae) nutrient medium supplemented with 2 mg/L 2.4-D or 0.2 mg/L TDZ was used. It was shown that the optimal sucrose concentration for embryogenesis was 30 g/L; at 70 g/L, embryogenesis was absent. The addition of 10 mg/L AgNO3 in combination with 2.4-D in the genotype Faraon increased the frequency of embryogenesis up to 80%. It was found that a low concentration of activated charcoal (5 mg/L) together with TDZ increased the yield of embryoids by 8.5 times (68% embryogenesis) in the genotype Sangrum. Both growth regulators effectively induce embryogenesis, but their action strongly depends on the genotype and the composition of the nutrient medium. Flow cytometry analysis of 247 regenerant plants adapted to ex vitro conditions of the studied genotypes obtained in this study showed that diploids (2n) accounted for 47.2%, tetraploids (4n) 45.7%, triploids 3.7%, and octoploids 3.4%. Genotype-specificity of growth regulator action was demonstrated: in the genotypes Sangrum and Faraon, TDZ promoted a higher yield of tetraploids, while in the genotype Yakor, 2.4-D was more effective. The obtained tetraploid lines can be used to create seedless triploid hybrids without colchicine treatment. The developed combinations of factors will allow more efficient induction of gynogenesis in summer squash in vitro.

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