Assessing phenotypic diversity and trait relationships within ( Syzygium cumini (L.) Skeels) using morpho-biochemical traits

Background Jamun ( Syzygium cumini (L.) Skeels) is a multipurpose fruit tree with notable nutritional, medicinal, and ecological potential. Uttar Pradesh, a major jamun growing state in India, harbours considerable variability in jamun, which remains underexplored. Methods To assess phenotypic variability and identify superior types, 123 genotypes of jamun were evaluated using morphological descriptors. Biochemical attributes were also assessed for a subset of 15 genotypes from the full panel. Results Significant variation was observed for most qualitative descriptors, with clear differences in tree growth and fruit morphology. Quantitative traits such as fruit weight (2.04–17.66 g), pulp content (61.12–94.38%), pulp: seed ratio (1.60–18.85) and total soluble solids (TSS, 10.64–19.96° Brix) exhibited wide ranges. Biochemical characterization of a subset of genotypes further revealed notable variation in ascorbic acid, anthocyanin content, and antioxidant-related traits, with genotypes Gn-10, Gn-11 and Br-17 showing favourable biochemical profiles. Correlation analysis indicated strong positive associations among fruit size traits (fruit length, diameter, and weight), whereas TSS showed negative correlations with fruit size and pulp-related traits. Cluster analysis based on morphological traits identified two major phenotypic groups, with the majority of genotypes forming a dominant cluster ( n = 114) and a smaller group ( n = 9) showing greater phenotypic divergence. Multitrait Genotype–Ideotype Distance Index identified Gn-18, Br-2, Br-14, Gn-11 and Un-6 as the most ideotype-consistent genotypes, based on fruit weight, pulp content and TSS. Conclusions While the present study highlights phenotypic diversity among the studied seedling-origin jamun trees, multi-year evaluations along with molecular characterization are needed to better elucidate the extent of diversity, the genetic basis of the observed trait differences, and the relationships among genotypes.