Comparative evaluation of red and white aril genotypes of Manila tamarind for fruit physicochemical and bioactive attributes

The cultivation and trade of underutilized fruits are gaining prominence worldwide, largely on account of their capacity to contribute to a nutritious diet. Manila tamarind [Pithecellobium dulce (Roxb.) Benth] is a fast-growing, nitrogen-fixing tree, with a fairly high tolerance to abiotic stresses. Despite significant potential in terms of food, fodder, timber, and medicine, it has largely remained an orphan crop. There is a dearth of systematic research on the exploration, conservation, and genetic improvement of Manila tamarind. Our study aimed to assess the genetic variability for commercially important fruit, aril, and leaf attributes in 22 diverse accessions of Manila tamarind comprising both white and red aril genotypes. Precise characterization of the existing genetic resources is a requisite for the commercial cultivation of Manila tamarind. The study was conducted with 15 white and 7 red accessions of P. dulce, which were planted in a square system of planting between and within row distances of 5 m each. One of the major contributions of the present study was that we examined genotypic variations in biochemical attributes, such as TSS, acidity, TSS: acidity ratio, total sugars, ascorbic acid, protein, mineral contents, and bioactive compounds; these factors significantly improve the nutritional value and eating quality of Manila tamarind arils. Most of the traits examined by us differed remarkably (p < 0.001) among the accessions. Some economically relevant traits, such as pulp weight, aril weight, aril total phenols, aril flavonoids, aril total antioxidant activity, and leaf flavonoids exhibited a high degree of variability, indicating the scope for the selection of elite genotypes and divergent parents for future hybridization programs. The highly variable values of total soluble solids (17.33-26.46 °Brix), acidity (0.54-1.07%), ascorbic acid (82.54-138.49 mg 100 g- 1), total sugars (12.45-18.81%), and aril protein (3.15-6.32%) recorded in this study broadly meet fresh consumption and aril processing standards for Manila tamarind. A significant finding was that Manila tamarind accessions differed greatly in aril mineral contents (mg/100 g FW), including potassium (220.44-334.33), phosphorus (21.63-62.34), and calcium (14.06-39.12). Overall, two red aril genotypes (CHESM-27 and CHESM-33), and three white aril genotypes (CHESM-4, CHESM-20, and CHESM-24) were found to be particularly promising in terms of pod and aril quality attributes. Our findings are expected to pay the way for commercial cultivation of elite Manila tamarind genotypes, and their applications in pharmaceutical applications. Future studies should aim to elucidate the molecular basis of genetic diversity and relationships in Manila tamarind.