The nature of the manifestation of heterosis is a reliable indicator of a high specific combination ability in a cucumber of the bee-pollinated type

Relevance. One of the most important stages in the selection of agricultural crops for heterosis is the determination of the combinational ability, in particular, the evaluation of the SCS constants of lines of promising hybrid combinations. Purpose: on the basis of the best hybrid combinations, create promising cucumber hybrids for open and protected ground, for various purposes, characterized by a complex of economically useful features, including high fruit yield. Objective: to evaluate the effects of true, hypothetical, competitive heterosis of hybrids and SCA line constants in the studied F1 hybrid combinations. Materials and methods. The research work was carried out in the Pridnestrovian Research Institute of Agriculture in 2014-2018 in greenhouses (spring-summer and summer rotations) and in open ground when growing in a spread and on a trellis. Much attention was paid to the degree and nature of the manifestation of heterosis in F1 hybrids, which were evaluated by early and total yield, the yield of standard fruits, the yield of gherkins and greens. The degree of manifestation of true, hypothetical and competitive heterosis of hybrids is established and the SCA constants in the studied F1 combinations are evaluated. The standards were the F1 Zubrenok hybrids of selection the Pridnestrovian Research Institute of Agriculture and Ajax of the Dutch selection. As testers, JL-6 and L.96 were used. In the studies, selection methods were used-pair and return crosses -backcrosses), self-pollination (incucht), selection (individual, group and mass). Results. With positive effects, all three types of heterosis (true, hypothetical and competitive) were observed in the spring-summer and summer rotations of film greenhouses and open ground when grown in a spread and on a trellis for most economically valuable traits in hybrid combinations 43x57 (seven traits); 71/55x41/86; 65x52 (six); 65x41/86, 65x96, 95x68 (five). High SCA constants were observed in film greenhouses (spring-summer and summer rotations) and in open ground (in the spread and on the trellis) lines in combinations 71/55x41/86 (early, general and standard fruit yield; gherkins yield fractions of 5.1-7.0 and 7.1-9.0 cm (+1.0; +0.9; +10.6; +1.2), (+1.8; +4.9; +39.8; +2.6), (+2.0; +4.4; +36.8; +2.6), (+1.1; +1.5; +12.9; +2.3); 65x52 (gherkins yield fractions of 5.1-7.0 cm) (+12.2; +7.2; +12.5; +7.0); 43x57 (yield of gherkins of the fraction 5.1-7.0 cm) (+1.0; +2.0; +6.7; +2.0).