Hardseededness in blackgram (Vigna mungo L.) is related to maternal environment during seed development

Hardseededness, characterized by a water-impermeable seed coat, is a common trait in blackgram that influences seed quality, cooking time, and tolerance to pre-harvest sprouting. Understanding environmental and genotype regulation of this trait could help identify the optimal season for enhancing seed quality and abiotic stress tolerance; however, this remains poorly understood. A panel of 127 blackgram genotypes was evaluated during the summer and rainy seasons over two consecutive years. Crop phenology, stage-specific weather variables, and seed physical traits were recorded and analysed to examine their relationships with hardseededness. Multivariate analyses were used to explore the association of phenological and climate factors with hardseededness and to identify stable genotypes with consistently high or low hard seeds. Seeds harvested during the rainy season had more hard seeds (40%-48%) compared to those from the summer season (3%-7%), irrespective of genotype. Combined ANOVA revealed that crop season was the major contributor to variability in hardseededness (72.7%), while genotype contributed 7.7%. Rainfall during the vegetative period, relative humidity during reproductive period, and longer maturity duration were positively associated with hardseededness, whereas higher maximum temperatures during the reproductive period negatively influenced this trait. Furthermore, there were seasonal variations in seed phenolic profiles, with p-hydroxybenzoic acid, catechin hydrate, and syringic acid showing positive associations with hardseededness. Genotypes PKJU1, CN35-15, WBU108 had the highest hardseededness during the rainy season, while IPU30, IPU99-23, PLU 44 had the lowest. The results highlight significant genotypic and seasonal influences on hardseededness in blackgram, offering valuable insights for improving seed quality. Genotypes identified to have either high or low levels of hard seeds can be utilized to improve pre-harvest sprouting tolerance or optimize germination, respectively.