Abstract:In order to understand the response of sweet potato (Dioscorea esculenta) to Ralstonia solanacearum, two varieties, including resistant ‘Xiangshu 75-55' and sensitive ‘Shenglibaihao’, were used as materials, the changes in photosynthetic characteristics, abscisic acid (ABA) content and chloroplast ultrastructure were studied after infected by R. solanacearum. The results showed that the membrane permeability (MP), intercellular CO2 concentration (Ci) and endogenous ABA content in ‘Shenglibaihao’ infected by R. solanacearum increased markedly, but chlorophyll (Chl) content, net photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductance (Gs) obviously decreased. Besides, the integrity of chloroplast membrane system was damaged, the number of chloroplast decreased, and expansion to collapse, the grana lamella loosed and disintegrated, and starch grains got smaller in ‘Shenglibaihao’ leaves affected. In contrast, for ‘Xiangshu 75-55', the changes in the related physiological indexes were not different significantly, and the plasma membrane and lamellar still kept integration. Therefore, there were distinct differences in the PMP, Chl content, ABA content, Pn and chloroplast structure between the two sweet potato varieties with different disease-resistance.