2017 ASHS Annual Conference

Vegetable transplants can be subjected to a high degree of mechanical stress during shipping and transplanting. Mechanical stress generally increases ethylene production and induces stress responses. Therefore, it was hypothesized that transplant performance is limited by ethylene-induced stress responses, and that inhibiting ethylene signaling in transplants prior to shipping can improve their growth and yield. To block ethylene receptors and inhibit ethylene signaling, 1-methylcyclopropene (1-MCP) was used 1-2 days before shipping or transplanting. Post-planting growth of tomato (Solanum lycopersicum L.) transplants was significantly accelerated by pre-plant treatments of 1-MCP at 12.5 and 50 mg/L, with plant height increasing by 7% to 12% at the flowering stage. At the time of harvest, 1-MCP treatments resulted in 17% to 19% increases in shoot biomass and 10% to 14% increases in flower number. Consequently, both extra-large fruit and total marketable fruit yields were significantly increased by 1-MCP by up to 51% and 25%, respectively. Yield increases by 1-MCP treatments were also observed for cucumber (Cucumis sativus L.) and muskmelon (Cucumis melo L.). Bioassay experiments using tomato, cucumber, and muskmelon transplants demonstrated that 1-MCP was effective in reducing stress responses induced by ethephon, such as leaf chlorosis and epinasty. Furthermore, root image analysis in rhizotron experiments revealed significant stimulation of root formation and elongation by 1-MCP. These results suggest that pre-plant 1-MCP treatment is highly effective in alleviating undesirable stress responses and improving the performance of vegetable transplants.