Assessment of phenotypic and genetic variability in Nepalese cucumber (Cucumis sativus L.) accessions

Abstract

Nepal harbours a rich diversity of cucumber landraces adapted to diverse agroecological conditions, but their phenotypic diversity remains largely unexplored. Eleven cucumber accessions collected from ten districts of Nepal were characterized and evaluated at the research field of the National Agriculture Genetic Resources Centre. Twelve quantitative and 16 qualitative agromorphological traits were measured following the International Union for the Protection of New Varieties of Plants (UPOV) guidelines. Diversity was assessed using descriptive statistics, Shannon-Weaver diversity index, principal component analysis, clustering, heritability analysis and phenotypic path analysis. Qualitative traits exhibited low to very high diversity (H′ = 0.44–0.99), while quantitative traits showed low to high diversity (H′ = 0.21–0.71). The first three principal components explained nearly 70% of the total variation, with leaf length, days to first female flowering, days to first male flowering, fruit breadth, length of peduncle, fruit length, and total yield as major contributors. UPGMA clustering grouped the accessions into four clusters with 80% similarity level. Phenotypic path analysis indicated that fruit size, fruit breadth, fruit length, leaf width, distance between the nodes and peduncle thickness were key determinants of yield. High heritability was observed for days to first male flowering, peduncle length, and stem diameter. Accessions CO14392 and CO13634, characterized by high yield potential (14.98t/ha) and superior fruit dimensions, were identified as the most promising for breeding programmes. These findings provide a foundation for utilizing Nepalese cucumber landraces, with multi-location and multi-year evaluations, complemented by molecular characterization to fully exploit their potential.