Comparative Analysis of Indicators to Time of Flowering in Mungbean (Vigna radiata L.)

Abstract

Flowering time is a critical adaptive trait in mungbean, with direct implications for yield potential, resource-use efficiency, and stress avoidance. Early-flowering genotypes may escape terminal stresses such as drought and heat, while late-flowering ones may benefit from longer vegetative growth in favourable environments. Mungbean (Vigna radiata L. Wilczek) is a short-duration pulse crop of economic and nutritional importance in Asia, with India being the leading global producer. Despite its potential, productivity remains low due to environmental stress at flowering during rainy season. The primary objective was to assess the reliability and consistency of GDD as a selection criterion for flowering time, and its potential application in improving the precision of mungbean breeding. In the present study, 270 genotypes were evaluated to assess the reliability of days to 50% flowering (DFF) and growing degree days (GDD) as selection traits across two contrasting seasons (Summer 2024 and post-rainy 2024–25). Phenotypic and genotypic coefficients of variation (PCV and GCV) were computed following the standard method. Genetic advance (GA) as a percentage of the mean was categorized as low (<10%), moderate (10–20%), and high (>20%). GDD showed higher genetic variability (GCV: 9.38%, PCV: 15.37%) than DFF (GCV: 5.73%, PCV: 9.87%). Heritability and genetic advance were also slightly higher in GDD. A weak but significant correlation (r = 0.135*, p < 0.001) suggests GDD captures temperature responses distinct from calendar days. Significant genotype × season interactions were observed for both traits. The significant genotype × season interactions for both traits highlighted the importance of multi-environment trials. GDD, in particular, offers a more climate-resilient measure of flowering time and could be a valuable trait for selection in breeding programs targeting stable adaptation under diverse seasonal conditions. Overall, GDD appears to be a more robust and physiologically meaningful trait for assessing flowering time, revealing its use in breeding for climate-resilient mungbean cultivars.