Genotypic variation in phenolic metabolites associated with kernel testa pigmentation in groundnut (Arachis hypogaea L.) before harvest and during ambient storage

Kernel testa colour in groundnut (Arachis hypogaea L.) is associated with phenolic metabolites that influence nutritional quality and post-harvest biochemical characteristics. Although biochemical differences among testa-pigmented genotypes have been reported, information on genotype-dependent biochemical profiles before harvest and their variation during ambient storage remains limited. This study evaluated six groundnut genotypes differing in kernel testa pigmentation (white, rose, light pink, and light red) under rainfed semi-arid tropical conditions using a Randomized Block Design (RBD) with three replications ( $$\:N=18$$ per sampling time point) to characterize biochemical variation before harvest and during post-harvest storage. Total phenols, flavonoids, and anthocyanins were quantified in pre-harvest leaves, whereas stored kernel samples collected at 30 and 60 days after harvest (DAH) were analysed for phenols, flavonoids, anthocyanins, total sugars, protein, and oil content. Significant genotype-dependent variation ( $$\:P<0.05$$ ) was observed for all evaluated biochemical traits. K-6 recorded higher phenolic ( $$\:5.70{\text{\:mg\:GAE\:g}}^{-1}\text{\:FW}$$ ) and anthocyanin ( $$\:0.347{\text{\:mg\:g}}^{-1}\text{\:FW}$$ ) contents in pre-harvest leaves, Dharani exhibited higher kernel sugar ( $$\:0.83{\text{\:mg\:g}}^{-1}\text{\:DW}$$ ) and protein ( $$\:25.64\%$$ ) contents, whereas Kadiri Lepakshi showed the highest oil content ( $$\:48.80\%$$ ). Total phenols, anthocyanins, and total sugars declined significantly during storage, although the rate of reduction and retention percentages differed markedly among genotypes (e.g., anthocyanin retention at 30 DAH ranged from $$\:32.0\%$$ in K-6 to $$\:80.3\%$$ in Narayani). Correlation analysis indicated positive associations between kernel phenols at 60 DAH and anthocyanins at 30 DAH ( $$\:r=0.87,P<0.05$$ ), while principal component analysis differentiated genotypes based on their distinct biochemical profiles. These findings demonstrate significant biochemical variability among groundnut genotypes and identify contrasting genetic materials with variable retention of kernel quality traits during ambient storage.