Effect of Tomato Rootstock on Hybrid and Heirloom Tomato Performance in a Midwest High Tunnel Production System

Abstract

High tunnels allow vegetable growers to extend the growing season, increase crop production, and improve produce quality. Tomatoes (Solanum lycopersicum L.) are the most widely grown crops in high tunnels; however, tomato production in high tunnels can be challenging. Continuous cropping in high tunnels can increase soil-borne disease pressure and can lead to soil salinity or nutrient depletion issues. Based on preliminary research, we hypothesized that use of the rootstock ‘RST-04-106-T’ would increase yield and quality of heirloom and hybrid tomato scions compared with nongrafted plants. To test this hypothesis, our research objectives were to assess marketable yields, fruit quality and nutritional value, and plant growth of grafted and nongrafted hybrid and heirloom tomatoes in a high tunnel production system. Grafted and nongrafted ‘Cherokee Purple’ (heirloom) and ‘Mountain Fresh Plus’ (hybrid) tomatoes were grown in the same high tunnel for two seasons (7 May–20 Oct. 2015 and 29 April–7 Oct. 2016) at the Horticulture Research Station in Ames, IA. Grafted plants produced significantly more marketable fruit, although marketable and total fruit weight did not increase significantly. Individual fruit size was unaffected by grafting. Across cultivars, mean soluble solids content (SSC) in fruit was 0.3 °Brix lower in grafted plants as compared with the nongrafted control. Grafting did not affect lycopene content of fruit. Grafting increased stem diameter by an average of 0.8 mm, but overall plant biomass was unaffected. The effect of grafting on leaf chlorophyll concentration (SPAD readings) was mixed. In addition, grafting increased leaf chlorophyll concentration in ‘Cherokee Purple’ but decreased it in ‘Mountain Fresh Plus’ plants. Grafting is a valuable tool in tomato production, but the impact of ‘RST-04-106-T’ rootstock use appears to be specific to certain soil types with high incidence of bacterial wilt.