Preliminary assessment of bambara groundnut (Vigna subterraneaL.) landraces for temperature and water stress tolerance under field conditions in Botswana

Abstract

Field experiments were conducted in 2006/07 and 2007/08 in Botswana to study the response of bambara groundnut to heat stress (2006/07 season) and to heat stress and soil moisture deficit stress (2007/08 season). In both seasons selected bambara groundnut landraces were grown at different sowing dates to provide a range of field environmental conditions. While the effects of water stress were mitigated by irrigation throughout the growing season in the 2006/07 season, in the 2007/08 season plants were grown under two irrigation regimes: a control that was irrigated throughout and a rain-fed treatment, with irrigation withheld at 30 days after sowing (DAS). Owing to significant and above average rainfall in the 2007/08 season no significant (p=0.05) differences in soil moisture content were obtained between the irrigated and rain-fed treatments. The highest average maximum temperatures of 34.1 and 29.2°C achieved in the December sowings in the 2006/07 and 2007/08 cropping seasons, respectively, did not impact any of the parameters measured, including leaf tissue electrolyte leakage, light adapted chlorophyll fluorescence, crop growth and yield. However, there was a highly significant (p<0.001) decline in crop performance with decline in temperature associated with delay in sowing after December. The results obtained suggest a sensitivity of bambara groundnut landraces to both low temperatures and photope-riod under field conditions in a semi-arid environment.