Drought affects protein and phenolic content in bambara groundnut (Vigna subterranea L. Verdc.)

Abstract

Bambara groundnut (Vigna subterranea L. Verdc.) is a legume crop, which has long been recognised as a protein-rich and drought-tolerant crop, used extensively in sub-Saharan Africa. This study evaluates the effect of experimental water deficit stress on total protein concentration, secondary protein structure and the total phenolics content on three Bambara groundnut landraces. Plants were grown in pots in a screen house. Water deficit was induced at the vegetative stage by withholding irrigation while fully watered plants served as control. Predominantly, β-sheet structure was observed in all the stressed as well as the control plants even though differences were observed between the treatments. Water deficit stress led to significant (P<0.05) increase in total protein content, but total phenolics content in all the landraces increased slightly. Drought stress induced significant increase in the synthesis of various proteins as part of the response strategy. The slight increase in total phenolics in the leaves of drought-stressed plants might be related to the antioxidant defence role of the phenolics. Correlation analysis of the total protein and phenolics indicated a strong positive relation across the three landraces studied. The results of the present work points to the resilience of the Bambara groundnut species to water deficit.

Keywords: Bambara groundnut, water-deficit, protein content, phenolics, FTIR spectroscopy