Grafting Compatibility in Heirloom Tomatoes

Heirloom tomatoes have always been popular at farmers’ markets for their heritage, novelty and premium price. However, the lack of pest-resistance and vigor limit the production of heirloom tomatoes for most farmers’ market vendors. Tomato grafting is an emerging technique in the United States which has the potential of providing disease resistance and enhancing vigor and yield for heirloom tomatoes, if appropriate rootstocks are utilized. The objective of this study was to investigate the grafting compatibility of heirloom tomatoes to selected rootstock species. Twenty-one heirloom varieties were chosen in the 2011 growing season and grafted onto Maxifort and Beaufort rootstocks using the silicon tube grafting method. Grafting success was above 90% for all combinations, reflecting no incompatibility issues. Grafted transplants were then planted in the field with non-grafted scion varieties as controls. The experiment was conducted as a completely randomized design with three replications. Visual observations on plant growth during the growing season did not indicate any incompatibility among grafted plants. Longitudinal slices at the grafted unions did not show any interruption in xylem and phloem tissues. Stem diameters measured at ½ centimeter below and above the graft union did not show significant difference, as indicated by the ratio of 1.05. Grafted Beefsteak, Brandywine, Durzba, Kentucky Beefsteak, and Auntie Ruby’s German Green had thicker stems than the non-grafted controls. In conclusion, all 21 heirloom tomato varieties grew well on Maxifort and Beaufort rootstocks and did not show any incompatibility problems. Yield and growth data of grafted versus non-grafted heirlooms will be discussed.