Genetic evaluation of diverse sex expression to improve earliness and yield in bitter gourd (Momordica charantia L.) hybrids

Abstract Background The basic sex form in bitter gourd is monoecious, characterized by a high male: female flower sex ratio of approximately 15:1. However, gynoecious and predominantly gynoecious lines have recently been developed, though they have not yet been commercially exploited to enhance earliness and yield potential. For the development of high yielding hybrids, it is crucial to identify promising parental lines for the genetic improvement of bitter gourd. In the present study, gynoecious, predominantly gynoecious and monoecious lines were used to develop and evaluate 64 hybrids with the objective to exploit the underlying genetic mechanism for earliness and high yield potential in bitter gourd. Methods Sixteen promising lines and four testers were crossed in a line × tester mating design to develop 64 F1 hybrids. These lines, testers and hybrids were evaluated for nine quantitative traits such as node number of first female flower, days to first female flower opening, days to first fruit harvest, average fruit weight (gm), fruit length (cm), fruit diameter (cm), number of fruits per plant, vine length (cm) and yield /plant (gm). Results The present results represent environment specific estimates with the mean values of F1 hybrids surpassed that of the parental lines and testers for all the traits except earliness where significant heterosis was observed in the desired negative direction. Gynoecious line, PVGy-201 was identified as most promising genotype for earliness and exhibited the highest yield per plant (1784.35 g), whereas DBG-34 produced maximum number of fruits per plant (46.18). Gynoecious line, PVGy-201 was good general combiner for earliness, whereas predominantly gynoecious line DBGS-21-06 for yield traits, and DBG-34 for number of fruits per plant. Hybrids like DBGS-21-06 × S-43 was identified as the most promising heterotic combination, exhibited significant heterosis for yield per plant (52.52%). The hybrid IC398610 × S-43 recorded the highest heterosis for average fruit weight (41.38%). Desirable negative heterosis for earliness traits was observed in PVGy-201 × G-16-2 for node number of first female flower (-55.53%) and days to first fruit harvest (-22.91), and in PVGy-201 × S-43 for days to first female flower opening (-16.87%). Furthermore, DBGS-21-06 × DBGS-2 exhibited maximum heterosis for fruit length (44.23%), DBGS-21-06 × G-16-2 for fruit diameter (31.25%), and DBGS-100-0 × G-23 for number of fruits per plants (42.90%) over the standard check cultivar Pusa Hybrid-6. The present findings are intended to identify potentially promising hybrids under the tested environment for further testing, not confirm the superiority. Conclusion The study has shown that gynoecious and predominantly gynoecious lines as a female parent in hybrid development of bitter gourd is highly useful for early harvest and high yield. The results represent preliminary genetic estimates derived from a single environment and provide a basis for selecting promising hybrid combinations for validation through multi-season and multi-location trials and can be exploited in segregating generations to identify inbred lines having earliness and high yield potential.