An Alternative Healing Method for Grafted Tomato Transplants: The Effect of Light Exclusion and Substrate Temperature on Plant Survival and Growth

Abstract

The use of tomato (Solanum lycopersicum) grafting is gaining traction across the United States, but small-scale growers face the challenge of creating optimum postgrafting healing conditions. The practice of blocking light for a period of 2 to 4 days while maintaining high humidity is commonly recommended for healing grafted tomato transplants; however, research is exploring alternatives to this practice. The present study investigated a low-input healing method for grafted tomato transplants with a specific focus on light and the use of propagation heat mats to regulate substrate and healing chamber air temperatures during the 7-day healing process. We hypothesized that 4 days of light exclusion and the use of propagation heat mats would improve grafted tomato transplant survival and growth. ‘Cherokee Purple’ was used as the scion and ‘RST-04-106-T’ was used as the rootstock. The whole plot factor was heat [propagation mats set at 80 °F (heat) or no propagation mat (no heat)] and the subplot factor was light exclusion (0, 4, or 6 days of dark). The highest survival rate among treatments was 97% in 0 days of dark with no heat treatment; survival decreased to 84% in 4 and 6 days of dark with no heat treatments. The plant survival rate was 96% with 0 days of dark and heat treatment; however, the survival rates were 63% and 45% for the 4- and 6-day dark treatments, respectively. The scion stem diameter was largest for transplants grown in 0 days of dark, but there was no difference in stem diameter due to heat treatments. There were no differences among scion or rootstock biomasses due to heat or light treatments. These results demonstrate that propagation mats set at 80 °F to regulate the substrate temperature were detrimental to grafted transplant survival under extended periods of light exclusion. However, this finding creates the basis to explore lower levels of substrate temperature modification. Our work also indicates that light exclusion may not be necessary for healing grafted tomato plants regardless of root-zone temperature treatments. Future work should examine the interactions of various substrate and air temperatures under full light conditions and their effects on grafted tomato transplant survival and growth. This work contributes to the ongoing research of how to optimize low-input healing methods that may be readily adopted by small-scale tomato growers.

Growth and Energy Use Efficiency of Grafted Tomato Transplants as Affected by LED Light Quality and Photon Flux Density

“…Therefore, the professional nurseries usually utilize healing chambers to provide a controlled environment for the healing of grafted transplants [4]. Many studies have focused on environment optimization in the healing stage for grafted transplants production in the greenhouse [5][6][7]. It is noteworthy that grafted tomato transplants have been commercially produced in the plant factory with artificial lighting (PFAL) for the advantages of high-quality, pesticidefree, and annual production [8].…”

Effects of daily light integral on tomato (Solanum lycopersicon L.) grafting and quality in a controlled environment

“…In the healing process of grafted seedlings, a suitable healing environment can effectively improve the healing rate and shorten the healing domestication period [3,4] . A great deal of research has shown that the time required for the connection of vascular tissue in tomato grafted seedlings can be shortened by more than 30% in a controlled environment [5][6][7] . As the source of energy and biological signals, light can influence the healing process by regulating the synthesis of the endogenous hormone, regeneration of wound-healing tissue, and connection of vascular tissue in grafted seedlings [8,9] .…”