EFFECT OF DROUGHT DURING EARLY REPRODUCTIVE DEVELOPMENT ON GROWTH OF CULTIVARS OF GROUNDNUT (ARACHIS-HYPOGAEA L) .2. BIOMASS PRODUCTION, POD DEVELOPMENT AND YIELD

Cultivars of groundnut (Arachis hypogaea L.) subjected to a period of reduced water supply during early reproductive development differed in growth responses during and following the period of water deficit. A Virginia type cultivar with a high harvest index (HI) under non water-limiting conditions, Q18801, yielded higher than Virginia Bunch (another Virginia type) and McCubbin (a Spanish type). During the period of water deficit, all cultivars produced a similar number of pegs and pods, but greater proportions of these were converted to pods in Q18801 and McCubbin than in Virginia Bunch. In all cultivars, water deficit delayed the start of the period of rapid pod growth by about 15 days and hence extended the time required to reach maturity. After rewatering, the number of pegs and pods and the leaf area index of Virginia Bunch and McCubbin increased rapidly. In contrast, Q18801 partitioned more assimilate to pods, achieving a higher average growth rate of individual pods, and consequently a higher total yield of pods and seed. While only three cultivars were examined, the implication of this result is that selecting cultivars with increased HI (via rapid pod growth at the expense of excess canopy growth) under irrigated conditions may also increase yields following a drought during early reproductive development.