Anatomy and physiology of graft incompatibility in solanaceous plants

SummaryGraft incompatibility in solanaceous plants was investigated using representative cultivars of tomato (Solanum lycopersicum L.), eggplant (Solanum melongena L.), and pepper (Capsicum annuum L.). Evaluations of the extent of graft (in)compatibility were made by examining survival percentages, fruit yields, and fruit quality in grafted plants. Tomato/pepper (scion/rootstock) and pepper/tomato grafts were considered severely incompatible, and the tomato/eggplant and eggplant/tomato grafts were considered moderately incompatible, when compared with the compatible homo-specific graft combinations of tomato/tomato, eggplant/eggplant, and pepper/pepper.Three, or 3 and 6 weeks after grafting, the dry weights of scions and rootstocks, carbohydrate concentrations in stems above and below the graft unions, scion mineral nutrient concentrations, water potentials of scions, and xylem hydraulic conductivities were measured in the grafted plants. The anatomy of the graft unions was also observed. Growth inhibition and high mortality in tomato/pepper and pepper/tomato grafts (i.e., severe graft incompatibility) was due to discontinuities in the vascular bundles at the graft union, which prevented the translocation of assimilates, mineral nutrients, and water between scions and rootstocks. Reductions in fruit yield and/or fruit quality of tomato/eggplant and eggplant/tomato grafts (i.e., moderate graft incompatibility) may have been due to differences in the requirements for assimilates and mineral nutrients between tomato and eggplant. Plant responses to graft incompatibility varied in solanaceous plants depending on the scion and rootstock combination.