Assessment of groundnut (Arachis hypogaea L.) genotypes for drought tolerance in Botswana

Abstract

Groundnut (Arachis hypogaea L.) production in Botswana is adversely affected by erratic and unpredictable rainfall resulting in various periods of drought. As part of a programme aimed at developing drought-tolerant cultivars, two field trials were conducted in the 2004-05 cropping season to evaluate 10 groundnut cultivars and 7 breeding lines from the University of Georgia, USA, together with two local varieties, for drought tolerance, using yield under stress and drought-susceptibility indices as selection indices. The trials were conducted under rain-fed and supplementary irrigation conditions at the Botswana College of Agriculture Farm, Notwane. There was a significant reduction in pod yield (P < 0.01), crop growth rate (P < 0.01) and partitioning coefficient (P < 0.01) due to drought stress. Pod yield across cultivars was reduced by an average of 2.3 t ha1 (79.3 %) and 3.5 t ha'1 (88.0 %), from the irrigated to the rain-fed treatment, for the cultivars and the breeding lines, respectively. Drought susceptibility indices for pod yield (Sy), crop growth rate (Sc) and partitioning to reproductive sinks (Sp), used together, identified three cultivars (GAG, 522 and 232) and two breeding lines (C24-124 and C209-6-49) as specifically tolerant to moisture stress. The control cultivars, Nakwana and Peolwane, had the lowest specific leaf area (SLA), 135.9 and 125.8 enrg’1, respectively, indicating high water-use efficiency (WUE) capacity. This variation in drought-tolerance traits could be exploited in a groundnut improvement programme.