Sweetpotato cultivar response to prolonged drought.

The sweetpotato (Ipomoea batatas) plant is tolerant to long periods of drought stress, although storage root yield and quality may be compromised. Root yield is particularly vulnerable to water restriction during the time of plant establishment, as any lignification of developing roots may impair their potential for the lateral thickening associated with carbohydrate storage. Sweetpotato cultivars vary in both their sensitivity and response to drought. In this field study, the growth of sweetpotato clones under prolonged natural drought conditions was compared with growth in a well watered environment. Throughout the growing season, some clones under drought stress underwent an atypical extended period of profuse flowering. While the canopies of clones grown under watered conditions exhibited complete ground coverage by season‟s end, canopies of drought-affected plants showed a range of clone-specific responses. Insects caused a greater degree of root damage at the water-stressed site, as soil cracking increased insect access to the roots. At harvest, three distinct drought yield responses were demonstrated: lowered root yield, unmodified yield, and increased root yield (P<0.001). The cultivar „Toka Toka Gold‟ demonstrated a 77% increase in marketable root yield under conditions of water stress, compared with that of the well watered site. The influence of drought on yield components differed with specific clones, both in the number of storage roots formed (P<0.001) and average root weight (P<0.001). Storage root quality was also affected, with the roots of some clones developing fluting along their main axes, while others were unaffected.