Grafting onto Tomato Rootstocks Improves Outcomes for Dry-farmed Tomato

Vegetable grafting can mitigate the negative effects of drought on crop production. Dry farming, which is the production of crops without irrigation during a dry growing season, can result in lower yields, smaller fruit, and a higher incidence of blossom-end rot (BER), which is a physiological disorder associated with drought stress. To determine the effects of grafting on yield and fruit quality of dry-farmed tomato (Solanum lycopersicum), three years of trials were conducted using different scion–rootstock combinations and ungrafted controls. In 2020, grafting onto rootstocks ‘DRO141TX’ and ‘Fortamino’ resulted in greater total yield and average fruit weight and a lower BER incidence for dry-farmed tomato than grafting onto the rootstock ‘Shincheonggang’ or using ungrafted plants. In 2021, grafting onto the rootstock ‘DRO141TX’ again increased yields and average fruit weight and decreased BER incidence when compared with ungrafted plants (‘Fortamino’ was not tested). Interactions were detected between different scion–rootstock combinations in terms of the degree of reduction of necrotic BER (BER resulting in a large, sunken, grey or black spot, making the fruit unmarketable) when grafted onto ‘DRO141TX’, with the scion ‘Azoychka’ having a 69% reduction in necrotic BER and the scion ‘Astrakhanskie’ having a 93% reduction in necrotic BER. In 2022, an interaction was detected between the rootstocks and scions in terms of their effect on large fruit (>0.33 lb) yield, with ‘BHN 871’ grafted onto ‘Fortamino’ producing the highest yields of large fruit and ‘Big Beef’ grafted onto ‘Fortamino’ producing the lowest yields. Overall, grafting onto the rootstocks ‘DRO141TX’ or ‘Fortamino’ improved diverse dry-farmed tomato outcomes in the Willamette Valley of Oregon, USA.