Genetic variability, trait association and yield determinants in kalingada [Citrullus lanatus (Thunb.) Matsum & Nakai]: implications for targeted crop improvement

Abstract

Kalingada is a nutritionally valuable yet underexploited cucurbit crop with substantial potential for genetic improvement. Effective selection requires a comprehensive understanding of the extent of genetic variability and the interrelationships among yield-contributing traits. Twenty-four kalingada genotypes were evaluated for fourteen morphological, yield-related and quality traits to assess genetic variability, trait associations and the contribution of individual traits to fruit yield. Considerable variability was observed among the genotypes, with total number of fruits per plant, total number of pickings, fruit length and fruit yield per plant exhibiting high phenotypic and genotypic coefficients of variation. These traits also recorded high heritability coupled with high genetic advance, indicating the predominance of additive gene effects and the potential effectiveness of selection. Fruit yield per plant exhibited significant positive associations with total number of fruits per plant, total number of pickings, days to last picking and primary branches per vine at both phenotypic and genotypic levels, whereas days to opening of the first female flower, days to first picking and total soluble solids (TSS) showed significant negative associations with yield. Path-coefficient analysis revealed that total number of fruits per plant and average fruit weight exerted the highest positive direct effects on fruit yield, while days to first picking, days to edible maturity, fruit length, total soluble solids (TSS) and days to last picking exhibited negative direct effects; however, fruit diameter and primary branches per vine, despite negligible direct effects, contributed to yield mainly through positive indirect effects via total number of fruits per plant. The results indicated that selection based on fruit number, picking frequency, fruit diameter and primary branches per vine could be effective for enhancing fruit yield in kalingada, whereas fruit weight, despite its high direct effect, showed limited net contribution owing to its non-significant correlation with yield, and the study provides useful information for future genetic improvement programmes