2017 ASHS Annual Conference

Large scale use of vegetable grafting is common in many states, but adoption has been slow in Midwestern states. This is slowly changing as small growers begin to utilize grafting. With limited resources and growing space, a challenge growers face is creating optimum post-grafting healing conditions. The practice of blocking light for a period of 2-4 days while maintaining high humidity is widely adopted, but some growers cannot afford to sacrifice valuable bench space needed for the healing chamber. This research investigated a low-input healing method for grafted tomato transplants with specific focus on light and root-zone temperature during the healing process. We hypothesized that light exclusion is not necessary and that use of root-zone heating would create optimum conditions for healing of grafted plants. Cherokee Purple was used as the scion and RST-04-106-T as the rootstock. Plants were grown in 606 cell packs and treatments were laid out in a randomized split plot design with four replications and 36 plants per experimental unit. The whole plot factor was root-zone temperature (26.6°C or no-heat) and the subplot factor was light exclusion (0, 4, or 6 days of light exclusion). Plants were grafted three weeks after seeding. Data collected from the time of grafting to termination included SPAD, chlorophyll florescence, plant survival percentage, scion stem diameter, and plant dry weight. Plant health indicators such as SPAD and chlorophyll florescence improved in the heated root zone treatment. Transplants that received six days of light exclusion had higher SPAD values. The use of root-zone heat and four days of light exclusion reduced plant survival to 72%. Survival percentage of transplants with no-light exclusion averaged 96% regardless of heat treatment. The scion stem diameter was highest for plants with no root-zone heat and no light exclusion. Overall, these results indicate that light exclusion and a heated root zone may not be necessary for healing of grafted plants and opens the door for a low-input graft healing method that may be readily adopted by small-scale tomato growers.