The Grafted Tomato System: Are There Advantages In the Presence of Soil Borne Diseases?

Tomato grafting is widely practiced internationally, mainly to confer resistance to soil borne diseases, to improve plant vigor, and to increase resistance to abiotic stressors. However, little work has been done in the U.S. to determine the benefits of grafting either in the presence or absence of soil borne disease. During the period 2005-2008 grafted tomato performance was compared with that of non-grafted and self-grafted (those grafted back on their own rootstock) tomato plants in replicated experiments on private farms and research stations in NC and one PA location. Grafted tomato plants demonstrated resistance on-farm to Southern Bacterial Wilt (Ralstonia solanacearum), Fusarium Wilt (Fusarium oxysporum), Root-knot Nematodes (Meloidogyne spp.), Southern Stem Blight (Schlerotium rolfsii) and Verticillium Wilt (Verticillium dahliae). In most cases, a lower disease incidence was present for tomato plants grafted on commercial rootstocks and was reflected in higher fruit yields. Although he relative advantage of grafted tomato transplants was greater when soil borne diseases were present, even in the absence of soil borne disease, no yield penalty was seen for grafted relative to non-grafted tomato plants. However, accurate diagnosis of the soil borne diseases likely to be present in the field is critical since no one rootstock was resistant to all the diseases encountered in our trials  In particular, the choice of rootstocks is limited for resistance to Southern Bacterial Wilt, Southern Stem Blight, and specific races of Verticillium and Fusarium Wilts.