Effect of seedling shoot removal on the yield of grafted tomatoes in high tunnels in the central United States

Grafting with inter-specific hybrid rootstock is an effective practice for tomato (Solanum lycopersicum) growers looking to reduce soilborne disease organically and increase fruit yield. However, production with grafted tomatoes has not been tested in the central United States and little knowledge exists of grafted plant performance in high tunnels, which are prevalent in the region. Small-acreage, high tunnel, and/or organic growers would like to produce grafted plants themselves, but many have difficulty with propagation. One way that growers may be able to reduce water stress during the post-grafting period is by removing the upper portion of the shoot in order to reduce leaf surface area. However, there currently exists no data that would indicate what this practice has on mature plant yield. Five high tunnel studies were conducted during 2011 and 2012 on commercial farms and a university research location to investigate any potential yield effects related to the use of 'Maxifort' and 'Trooper Lite' rootstocks and shoot removal during the grafting procedure. The implementation of grafted plants significantly affected fruit yield in four out of the five trials (P<0.05). Increases in fruit yield ranged from 18 to 126%. The average yield increases of 'Maxifort' and 'Trooper Lite' rootstocks 53 and 51%, respectively. Our data suggest that shoot removal may penalize mature plant yield and is dependent upon rootstock vigor. For growers wishing to perform tomato grafting using this technique, careful consideration should be made to determine optimum rootstock and scion combinations for successful implementation of this technology.