Genetic evaluation of bioactive compounds and mineral nutrients in bitter gourd (Momordica charantia L.) using heterosis and combining ability approach

Bitter gourd is an economically important vegetable of Cucurbitaceae family, rich in bioactive health compounds, minerals and antioxidants, including carotenoids and ascorbic acid. These quality traits exhibit high genetic variability among genotypes but very limited efforts have been made to identify superior genotypes and improve these traits through hybrid breeding. The development of gynoecious, predominantly gynoecious and monoecious inbred lines offers great opportunities for the breeding of varieties and F 1 hybrids for higher yield and nutritional traits. The genetic improvement of bitter gourd for nutritional traits depends on identifying superior parental lines and cross combinations rich in these nutrients. A line × tester mating scheme was used to develop 64 F 1 hybrids by crossing 16 genetically diverse lines including gynoecious, predominantly gynoecious, and monoecious lines with 4 testers. These 16 lines, the 4 testers and the 64 F 1 hybrids were evaluated for 7 bioactive and antioxidant compounds including chlorophyll a and b (µg g⁻¹ FW), total carotenoids at edible and ripening stages (µg g⁻¹ FW), vitamin C (mg 100 g⁻¹ FW), saponins and charantin (µg g⁻¹ FW) along with 5 essential minerals, including calcium, magnesium, iron, zinc and manganese (mg 100 g⁻¹ DW). To determine the underlying genetic mechanisms controlling these traits, combining ability and heterosis were evaluated in 20 parental genotypes and 64 F 1 hybrids. The parental lines and hybrids showed significant genetic variation for all the nutritional traits. The parental lines DBGS-100-0, IC398610, PVGy-201, DBG-38, DBG-4-1 and S-43 exhibited superior mean performance and favourable GCA effects for the studied traits. The hybrids DBGS-100-0 × S-43, PVGy-201 × G-16-2, PVGy-201 × S-43, IC398610 × G-23, DBG-100 × G-23, and IC398610 × DBGS-2 recorded high mean values, significant positive SCA effects, and standard heterosis for bioactive and antioxidant compounds, and essential mineral nutrients. Several hybrids exhibited significant positive heterosis (> 50%) for carotenoids, vitamin C, charantin and mineral nutrients, with DBGS-100-0 × S-43, PVGy-201 × G-16-2 and IC398610 × G-23 emerged as the most promising combinations. The hybrid, PVGy-201 × G-16-2 had the highest standard heterosis for charantin (61.58%) and Fe (113.39%), whereas the hybrids DBG-4-1 × S-43 (26.51%), IC398610 × S-43 (86.39%), DBGS-100-0 × S-43 (32.50%), and IC398610 × DBGS-2 (112.18%) showed superior standard heterosis for Mg, Mn, Ca, and Zn, respectively. Hierarchical clustering-cum-heat map analysis revealed variability among hybrids and grouped into seven clusters with distinct profiles for bioactive and antioxidant compounds, and mineral nutrients. PCA and clustering analyses identified phenotypically divergent hybrids based on the evaluated nutritional traits, facilitating parent selection for future breeding. The present study demonstrated genetic variability and significant heterosis for most nutritional traits. The identified superior parental lines can be used in breeding programs to develop nutritionally superior hybrids, followed by nutritional stability analysis before their commercial release.