Scion shoot removal and rootstock cultivar affect vigor and early yield of grafted tomatoes grown in high tunnels in the central United States

Grafting with interspecific hybrid rootstock is effective for tomato (Solanum lycopersicum) growers looking to reduce soilborne disease in the southeastern United States. However, production with grafted tomato has not been tested in the central United States, where soilborne disease pressure is low. Smallacreage growers would like to produce grafted plants themselves, but many have difficulty with propagation due to water stress in the scion postgrafting and/or high temperatures. Removing the upper portion of the scion to reduce leaf area during the grafting procedure [shoot removal (SR)] could help to reduce water stress postgrafting, but there are no data available that indicate what effect this practice has on tomato yield. Five high tunnel trials and one open-field trial were conducted in 2011 and 2012 to investigate potential yield effects related to the use of two rootstocks and SR during the grafting procedure. The implementation of grafting with rootstocks significantly increased fruit yield in five of the six trials (P > 0.05). The average yield increases by ‘Maxifort’ and ‘Trooper Lite’ tomato rootstocks were 53% and 51%, respectively, across all trials. SR during the grafting process may penalize tomato yield and our results suggest that rootstock vigor plays a role. Plants grafted with ‘Maxifort’ across all of the trials consistently increased shoot biomass in four of five of the high tunnel trials compared with nongrafted plants (P > 0.05), whereas plants grafted with ‘Trooper Lite’ rootstock increased shoot biomass in one trial. Similarly, the SR method penalized the total fruit yield of plants grafted with ‘Trooper Lite’ more often than those that were grafted with ‘Maxifort’. Our results suggest that plant growth and ultimately tomato fruit yield is affected negatively by using the SR grafting technique, particularly when less vigorous rootstock is used.