Water-requirement characteristics of two cassava varieties

[Objective]This experiment was conducted to discuss the water-requirement characteristics of cassava varieties SC 205 and Xinxuan 048 and to provide scientific basis for cassava cultivation and drought resistance breeding. [Method]Cassava varieties SC 205 (main variety grown in Guangxi) and Xinxuan 048 (bred by Guangxi University) were taken as test materials; four treatments, viz., (A) normal water supply (CK), (B) mild drought, (C) moderate drought, and (D) severe drought, were set. The net photosynthetic rate, leaf water potential, leaf membrane permeability, chlorophyll a+b, MDA, PRO, and biomass were measured during the cassava root tube formation period (from May to July) and expanding period (from July to September), and maturity(Sep. to Dec). [Result]The water-stress time of SC 205 was earlier than that of Xinxuan 048. The influence of water-stress on cassava was more obvious in the late growth period. The photosynthesis efficiency of cassava leaves was affected by water stress under drought condition. However, the compensation effect of water stress on the photosynthesis efficiency was likely to appear under the mild and moderate drought conditions. [Conclusion]The order of cassava physiology responses to drought stress was as follows: photosynthetic rate transpirationstomatal conductanceleaf water potential. The appropriate water stress was beneficial to cassava yield formation and starch accumulation. Cassava variety Xinxuan 048 showed stronger drought resistance than that of SC 205 under this experimental condition.