Morpho-biochemical insights into globally collected guava germplasm (Psidium spp.): opportunities for utilization in breeding

BACKGROUND: century, guava cultivars have exhibited a narrow genetic base, with most existing genotypes arising from open-pollinated selections or crosses involving a limited number of genotypes. Furthermore, much of the available germplasm has been named based on fruit characteristics or place/regions of origin, leading to confusion in classification and hindering the precise identification and utilization of genetic resources in guava breeding programs. To address this, 49 morpho-biochemical parameters were assessed in 51 diverse Psidium genotypes, including cultivars, varieties, hybrids, related wild species, and exotic/USDA introductions. RESULTS: Substantial variability was observed among globally collected guava germplasm for fruit traits, with fruit weight ranging from 11.67 g (Psidium molle) to 379 g (S. N90-53), seed number from 8 (S. N11-3) to 512 (S. N15-3), leaf length from 5.57 to 17.17 cm, leaf width from 2.07 to 7.90 cm, and petiole length from 0.17 to 0.77 cm. Germplasm also differed in qualitative descriptors, including branch orientation, bark colour, leaf morphology, tip structure, and fruit surface traits, with wild species forming distinct morphological groups. Additionally, biochemical traits varied widely, including the contents of total soluble solid (6.8-13.8 °Brix), acidity (0.25-1.60%), total sugars (3.62-9.21 g/100 g FW), ascorbic acid (88.36-302.46 mg/100 g FW), ferric reducing antioxidants power (7.74-20.69 µM TE/g FW), free radical scavenging activity (2,2-diphenyl-1-picrylhydrazyl assay)(85.72-98.47%), lycopene (0.05-8.91 mg/100 g FW), and total carotenoids (0.05-2.76 mg/100 g FW). Besides, principal component analysis indicated PC1 (22.1%) related to fruit size and PC2 (15.2%) to biochemical traits. Furthermore, cluster analysis grouped 51 guava genotypes into three clusters, distinguishing wild from cultivated types. CONCLUSIONS: The study confirms the presence of wide morpho-biochemical variability in Psidium germplasm, offering valuable genetic resources for genetic improvement programs, aimed at enhanced fruit quality with rich antioxidants, bio-fortification, and the tailoring of novel guava genotypes with reduced seed content, enhanced seed mellowness, and tenet branching, fitting in high-density planting and improved yield efficiency.