Assessment of the potential of wild Ipomoea spp. for the improvement of drought tolerance in cultivated sweetpotato Ipomoea batatas (L.) Lam

Sweetpotato [Ipomoea batatas (L.) Lam] is cultivated worldwide, and it is a staple food in many developing countries. In some regions (e.g., Africa) drought is a major production constraint that results in significant yield loss. Climate change is predicted to result in even greater losses due to long periods of drought and elevated temperatures. The goal of this study was to assess the potential of wild Ipomoea spp. as a source of drought tolerance in cultivated sweetpotato. We evaluated the drought tolerance of I. batatas, I. cynanchifolia, I. leucantha, I. trifida and I. triloba in a randomized complete block design, with five levels of simulated drought: control (daily irrigation), and no irrigation for 7, 9, 21 and 50 days. We observed that post drought re-irrigation of the wild species subjected to 21 days of stress resulted in plant recovery and an increase of the stomatal conductance of up to 99% in I. leucantha. However, under extreme stress (50 d) the wild plants did not respond to re-irrigation, resulting in up to 89% (I. leucantha) plant mortality. The wild species did not produce storage roots, while the I. batatas cultivars produced storage roots. Under 50 days of stress I. batatas had a survival rate between 44% (cv. Tanzania) and 89% (cv. Beauregard). We concluded that the wild genotypes screened may not be a valuable source of germplasm for drought tolerance and that significant levels of drought tolerance may exist in cultivated sweetpotato.