The effect of different gelling agents as part of culture medium on the rate of cucumber (Cucumis sativus L.) unpollinated ovules gynogenic development

Relevance. The induction of gynogenic development of the culture of unpollinated ovules of Cucumis sativus L., as a part of solid nutrient media agar-agar or Phytagel™ are used as a gelling agent. The gelling agent determines the mobilization of substances in the composition of the nutrient medium and has various effects on the explants, which affects the quality of the resulting regenerates. However, there are no scientific works that explaines the effect of these gelling agents on the development of ovules and compare them with each other for C. sativus L. The aim: investigate the effect of various gelling agent in the nutrient medium on the induction of gynogenesis and the development of cucumber unpollinated ovules.
Materials and methods. There are two promising collection specimens of cucumber №58 and №831 of the laboratory of cucurbits crop breeding and seed production of FSBSI FSVC were included into research. IMC nutrient medium (Induction Medium for Cucurbitaceae) with 30 g/l sucrose, 200 mg/l ampicillin, 0.2 mg/l thidiazuron (TDZ) was used for the induction of gynogenesis; agar-agar at a concentration of 7 g/l or Phytagel™ at a concentration of 3.5 g/l was used as a gel-forming agents. Ovules were isolated from ovaries in the phase of half-opened flower (FL-1) and fully opened flower (FL). Cultivation was carried out in plastic Petri dishes with a diameter of 60 mm with an air gap of 28.8 cm³ – "KS No. 1", and glass culture jars with an air gap of 140 cm³ – "KS No. 2".
Results. On containing Phytagel™ or agar-agar nutrient medium, the area of ovules during 30 days of cultivation increases irregularly. Coefficients of ovule enlargement between gelling agents differed from 1.7 to 2.6 times depending on the cultivation time. The average growth rate of ovules on media with Phytagel™ was 0.08 mm²/day, while on media with agar-agar it was 0.02 mm²/day. Gelling agents type and cucumber phenotype are significant factors affecting the increase in area of entered into unpollinated cucumber ovules culture. Herewith the share of the gelling agent effect was 55.01%, and the share of genotype effect was 14.53%. The effect of flower development stage or culture vessel type has not found for both of genotypes. In the study, it was possible to achieve the induction of gynogenesis in 67% of the unpollinated ovules genotype №831 on nutrient medium with agar-agar.
Conclusion. Ovules development were faster on a nutrient medium using Phytagel™ as a gelling agent than on agaragar. At the same time, the percentage of induced ovules was significally higher on nutrient medium with agar-agar for both phenotypes. Gelling agents type and cucumber phenotype were found as significant factors of the induction and the development of unpollinated ovules.

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