2018 ASHS Annual Conference

In the absence of soil-borne disease, tomatoes grafted to hybrid rootstock RST-04-106-T showed minimal yield increase. This result indicates the need for more trials of tomato rootstocks that meet the need of localized soil conditions in the Midwest, and our additional research was designed to address this gap in localized roostock performance data. We hypothesized that alternative rootstocks would outperform non-grafted plants even without the effect of soil-borne disease. Our research objectives were to assess marketable yield, fruit quality (soluble solids, titratable acids, and firmness), and plant growth characteristics (SPAD, plant height, stem diameter, petiole-sap, and biomass) of eight different hybrid tomato rootstocks compared to a self-grafted and non-grafted control. Hybrid tomato BHN 589 was grafted to all rootstocks in addition to non-grafted and self-grafted controls. The roostock treatments included commercially available Arnold, Beaufort, DRO141TX, Estamino, Maxifort, RST-04-106-T, and two trial rootstocks not yet commercially available, 946 TRS and 980 TRS. This research took place during 2017 in a 9.1 × single-poly high tunnel in central Iowa. There were five plants per plot in a randomized complete block design with five replications. The crop was harvested thirteen times between 5 July and 27 September. Non-grafted and self-grafted plants had the lowest marketable yield per plant with means of 5.5 and 5.6 kg respectively. Plants grafted to Maxifort, DRO141TX, and Estamino had the highest marketable yield ranging from 8.1 to 8.6 kg per plant. Fruit total soluble solute concentration ranged from 4.6 ⁰Brix (Maxifort rootstock) to 5.4 ⁰Brix (RST-04-106-T rootstock). Estamino and Arnold had the largest mean root biomasses of 21.0 and 19.1 g, respectively. Shoot biomass was largest for tomatoes grafted on Maxifort (323.1 g) and Estamino (320.7 g) rootstocks. Our results indicate that grafting tomatoes may still be a viable option for Iowa vegetable growers even in the absence of soil-borne disease. This work identifies several rootstocks that are well-suited for high tunnel production systems in the Midwest.