Assessment of genetic divergence in bottle gourd (Lagenaria siceraria) germplasm using Mahalanobis’s D2 statistic for parental line selection

Abstract

An investigation was conducted to assess the genetic divergence among 24 genotypes of bottle gourd (Lagenaria siceraria) to identify suitable parental lines for future breeding programs. The experiment was laid out in a randomized block design with three replications during the spring season of 2024. Quantitative data for 17 traits were analysed using Mahalanobis’s D2 statistic. The genotypes were grouped into 7 distinct clusters, with cluster 1 being the largest with ten genotypes, followed by cluster 2 with seven genotypes, followed by cluster 3 with three. The remaining four clusters were small, each containing one genotype. Analysis of cluster means revealed significant diversity across the genotypes. Cluster 4 exhibited the most desirable traits, showing the longest fruit length (42.567 cm) and the highest average fruit weight (1213.333 g). In contrast, cluster 6 had the highest number of fruits per plant (11.557) and the shortest harvest period (49.777 days). The average intra-cluster distance was lowest for the single-genotype clusters (0.000) and highest for cluster 2 (260.826). The inter-cluster distance, which indicates the level of diversity between groups, was found to be highest between cluster 3 and cluster 6 (2361.074), suggesting these groups are the most genetically distant. Conversely, the smallest inter-cluster distance was observed between cluster 5 and 6 (400.438). The character contributing most to the overall divergence was average fruit weight (34.84%), followed by days to first female flower anthesis (20.91%) and days to first fruit harvest (13.96%). These findings suggest that genotypes from the most divergent clusters, such as those from cluster 3 and 6, should be selected for hybridization programs to create superior recombinants with a broad genetic base.