Genetic studies in cucumber Cucumis sativus L using gynoecious lines

Abstract

The present investigation was carried out on three major aspects: (I) Inheritance study for gynoecious sex expression (II) Generation mean analysis for yield and component traits in cucumber, and (III) Isolating desirable segregants of gynoecy. In addition to the three major objectives: (IV) QTL mapping of flowering traits and mapping of gynoecious (F) locus in Indian gynoecious cucumber line HPK-1 was done. The results of generation mean analysis showed the significance of additive, dominance and epistatic interaction in most of the crosses for twenty important quantitative characters. Simple mass selection would be effective for improvement of the characters governed by additive gene effects, heterosis breeding for characters governed by dominance gene effects and breeding plan based on restricted selection by way of intermating the most desirable segregants followed by selection and/or diallel selective mating system would be most appropriate for characters where duplicate epistasis was predominant. Segregating population showed that gynoecy in genotype Him Palam Kheera-1 and Punjab Kheera-1 is controlled by single dominant gene. The consistency in trait expression across both generations reflects the stability of gynoecy and its suitability for use in breeding programs. The total 14 desirable segregants from F2 and 19 from B1F2 were isolated. The isolated segregants from both generations offer a valuable genetic resource for the development of high-yielding, early-flowering gynoecious lines and can be further utilized in hybrid breeding or varietal improvement programs. QTL mapping highlighted chromosome 6 as a major hotspot for QTLs controlling multiple flowering and sex expression traits in cucumber. The region flanked by SSR11742 and SSR11858, in particular, was consistently associated with QTLs for days to first female flower, nodal position of first female flower, and number of female flower per node, suggesting tight linkage. The gynoecious F locus was closely linked with two markers i.e., UW020605 and SSR19165 at 0.3 and 2.5 cM distances respectively. These genomic regions offer significant potential for marker-assisted selection (MAS) and can be effectively used in cucumber breeding programs to develop early flowering and high-yielding gynoecious lines. newline