Grafting Enhances Bacterial Wilt Resistance in Peppers

Ralstonia solanacearum is a causative agent of bacterial wilt and therefore poses a serious threat to cultivated peppers ( Capsicum annuum L.). Although attempts have been made to control bacterial wilt by grafting, the disease resistance mechanisms that protect grafted peppers are poorly understood. Here, we grew grafted peppers composed of the rootstock Buyeding or Weishi and the scion Xinfeng 2. Following infection by R. solanacearum , we assessed the differences in lipid peroxidation, cellular structure, root secondary metabolism, and biomass, between grafted plants and controls. The grafted plants exhibited a greater root biomass than the control plants after infection. The root cell ultrastructure of the grafted plants showed only slight injury relative to that in the controls, and the roots of the grafted peppers were partially resistant to R. solanacearum. Grafted pepper plants showed lower levels of lipid peroxidation. Lignin content, salicylic acid levels, and the activities of phenylalanine ammonia lyase (PAL), peroxidase (POD), catalase (CAT), and polyphenol oxidase (PPO), were also higher in grafted plants. All of these effects occurred concomitantly with increased R. solanacearum resistance. Taken together, our findings demonstrate that grafting can significantly improve the disease resistance of pepper. Moreover, our results suggest that the Weishi rootstock may be very useful for the prevention and control of bacterial wilt in cultivated peppers.