Effect of Healing Chamber Design on the Survival of Grafted Eggplant, Tomato, and Watermelon

Abstract

<jats:p>Successful grafting of vegetables requires high relative humidity (RH) and optimal temperatures for ≈1 week following grafting to reduce transpiration of the scion until rootstock and scion vascular tissue are healed together and water transport is restored. This study evaluated the effect of three healing chamber designs on the survival of grafted eggplant (<jats:italic>Solanum melongena</jats:italic>), tomato (<jats:italic>Solanum lycopersicum</jats:italic>), and watermelon (<jats:italic>Citrullus lanatus</jats:italic>). The three healing chamber designs were 1) an industry design, which was hand-misted, 2) a research design, which contained a humidifier, and 3) a simplified design, which was shadecloth only and hand-misted. All plants were self-grafted using the splice grafting technique, placed in the healing chamber for 7 days after grafting and evaluated for signs of wilting and graft failure from day 6 to day 14 after grafting. During the 7-day healing period, the industry design had the greatest fluctuation in temperature, the research design had the greatest fluctuation in RH, and the shadecloth only design had the least fluctuation in both temperature and RH. When the healing chambers were closed on day 2 after grafting, the industry healing chamber had higher mean temperature and RH (24.9 °C, 98%) than both the research (23.4 °C, 81%) and shadecloth only (23.3 °C, 52%) healing chambers. These results suggest that a humidifier may not be necessary to maintain high RH. Mean graft survival rates in the industry (69%) and research (66%) healing chambers were similar, and both were higher than that in the shadecloth only healing chamber (52%). Tomato had the highest rate (98%), eggplant was intermediate (82%), and watermelon had the lowest mean survival rate (7%); there was no interaction between healing chamber and crop. The very low survival rate of watermelon was most likely due to the grafting technique used in this study, which is not optimal for watermelon. Tomato graft survival was high in all three healing chambers (96% to 98%), suggesting that high RH is not essential for tomato graft survival. Eggplant graft survival decreased from 90% to 60% when RH was decreased, suggesting that high RH is essential for eggplant graft survival.</jats:p>

Sunflower (Helianthus annuus L.) organogenesis from primary leaves of young seedlings preconditioned by cytokinin

“…Greenhouse-grown plants have previously been used as rootstock for grafting of sunflower shoots, but the scion in those cases was well developed (Burrus et al 1996;Weber et al 2003). As graft healing strongly depends on the environmental conditions (Johnson and Miles 2011), grafting success in the greenhouse can be impacted by temperature fluctuation, plant dehydration, and fungal contamination. In contrast, the growth conditions for the in vitro seedling rootstocks used here were precisely regulated, where survival of small shoots could be better controlled.…”

Cucurbitaceae Germplasm Resistance to Verticillium Wilt and Grafting Compatibility with Watermelon

“…Seedlings were grafted on 4 June using the one-cotyledon method, and plants were healed using a protocol developed for grafted watermelon at this experimental site . Seedlings were placed in a dark, humid healing chamber (Johnson and Miles, 2011) and were gradually reintroduced to light and greenhouse conditions over an 8-d healing period.…”

Microclimate and Scion Leaf Removal to Improve the Success of Grafted Tomato Seedlings

“…It should also be noted that this is a typical timeline for propagating grafted plants in the central United States and therefore reflects what a propagator in the region would experience. The role of water vapor pressure plays a role during graft healing (Johnson and Miles, 2011). As temperatures increase throughout the day, warmer air permits a greater water-holding capacity and if the actual water vapor content in the area remains constant, the relative humidity will decrease as temperature increases.…”

“…On the basis of industry and extension technical publications, the current recommended temperature range for healing chambers is 28 to 29°C, and the recommended range for relative humidity is 85% to 100% (De Ruiter Seeds, 2006;Rivard and Louws, 2011). Johnson and Miles (2011) noted that tomato might be more tolerant of higher temperature and variable relative humidity (and thereby require less maintenance) than other horticultural crops such as watermelon. However, systematic experiments have not been published that quantify the effects of temperature and humidity on graft survival.…”