Water deficit stress enhances the bioactive compounds of groundnut (Arachis hypogaea L.) kernels at the expense of primary metabolites

Water deficit stress and pod developing stages affect the biosynthesis of primary and secondary metabolites thereby altering nutritional composition of groundnut kernels. Two groundnut genotypes (GJG-22 and TG-37 A) were grown under normal and water-deficit conditions in the field. Biochemical traits of the genotypes were measured at three pod-developing stages (90, 105, and 120 days after sowing). The results showed that groundnut kernels' oil percentage increased with maturity with a significant decrease in sugars and protein content in the control set (P < 0.005). Among the fatty acids, linoleic and palmitic acids were increased, while oleic acid decreased in both varieties under water deficit conditions, thereby reducing the oleic to linoleic acid ratio (O/L ratio). Water deficit stress resulted in increased trehalose and tocopherol content. Phenolics profiling revealed accumulation of p-coumaric acid (3-6 folds), and resveratrol (2-3 folds) in water deficit treatment at all the stages. While a toxic compound catechol decreased due to water deficit stress and maturity. Rutin, the major flavonoid detected in groundnut, increased during the S1 and S2 phases in both the genotypes under stress conditions over the control. Protein and sugar content had a positive correlation (0.46) while both protein (-0.23) and sugar content (-0.35) had a negative correlation with oil content. Overall primary metabolites showed a negative correlation with bioactive compounds. These findings revealed that water deficit stress at different pod-developing stages increases bioactive compounds in groundnut kernels.