Physiological responses of groundnut (<i>Arachis hypogaea</i> L.) to drought stress and its amelioration: A review

Groundnut (<i>Arachis hypogaea</i> L.) is an important cash crop for tropical farmers. It is an annual legume and its seeds contain high amounts of edible oil (43-55%) and protein (25-28%). Even though it is fairly drought-tolerant, production fluctuates considerably as a result of rainfall variability. To develop a water stress response function in groundnut, research has been done to improve the performance under varying degrees of stress at various physiological stages of crop growth. This review summarizes recent information on the drought resistance characteristics of groundnut with a view to developing appropriate genetic enhancement strategies for water-limited environments. It is suggested that there are considerable gains to be made in increasing yield and stabilizing the yield in environments characterized by terminal drought stress and further exploiting drought escape strategy, by shortening crop duration. Many traits conferring dehydration avoidance and dehydration tolerance are available, but integrated traits, expressed at a high level of organization, are likely to be more useful in crop improvement programs. Possible genetic improvement strategies are outlined, ranging from empirical selection for yield in drought environments to a physiological-genetic approach. It is also suggested that in view of recent advances in understanding drought resistance mechanisms, the latter strategy is becoming more feasible. It is concluded that the use of this recently derived knowledge in a systematic manner could lead to significant gains in yield and yield stability in the world's groundnut production. Research is needed to develop transferable technologies to help farmers in arid and semi-arid regions. Increasing soil moisture storage by soil profile management and nutrient management for quick recovery from drought are some of the areas which need to be explored.