Growth, phenological and yield responses of a bambara groundnut (<i>Vigna subterranea</i> L. Verdc) landrace to imposed water stress: II. Rain shelter conditions

Abstract

Bambara groundnut is a protein-rich legume, with food-security potential. Effects of irrigation levels and seed coat colour on growth, development, yield and water-use efficiency of local bambara groundnut landrace selections were evaluated under a rain shelter. Emergence was slow, although variation was indicated between landraces. Limited water availability was shown to lower stomatal conductance, although chlorophyll content index was shown to be unaffected. Additionally, growth indices of plant height, leaf number and leaf area index were shown to be lower in response to decreasing water availability. Furthermore, landraces generally flowered and matured earlier while also demonstrating higher water-use efficiency at lower water availability. Seed yield was lower under limited water availability resulting from lower pod mass and pod number. Drought tolerance in bambara groundnut landraces was achieved by reduced canopy size, early flowering and maturity, and maintaining high water use efficiency under stress. ‘Brown’ and ‘Red’ landraces responded to water stress better than the ‘Light-brown’ landrace, suggesting an effect of seed colour on possible drought tolerance.