2017 ASHS Annual Conference

High tunnels have emerged as a tool for vegetable growers to extend the growing season, increase crop production, and improve produce quality, but tomato production in this system does not come without challenges. Continuous cropping of tomatoes in a high tunnel production system gives rise to recurring soil-borne and foliar diseases and increased pest pressure. We hypothesized that tomato grafting would overcome those challenges through increased plant vigor conferred by a proven, disease-resistant rootstock, RST-04-106-T. Our research objectives were to assess marketable yields, fruit quality and nutritional value, and plant growth characteristics of grafted and non-grafted hybrid and heirloom tomatoes in a high tunnel production system. Grafted and non-grafted Cherokee Purple (heirloom) and Mountain Fresh Plus (hybrid) tomatoes were grown in the same high tunnel for two seasons, 2015 and 2016, in a randomized complete block design. Each plot had 10 plants, and there were four replications. Grafted plants had an increase in the number of marketable fruit, but did not have an increase in marketable fruit weight. Fruit size was not affected by grafting, but other quality parameters suffered. The average total soluble solid in fruit was 0.3 degrees lower in non-grafted plants. Grafting did not increase lycopene content of tomato fruit as analyzed by using a tetrazolium assay. Grafting increased stem diameter but did not increase plant biomass. The effect of grafting on SPAD reading was mixed. Grafting increased SPAD reading in Cherokee Purple but decreased SPAD in Mountain Fresh Plus plants. Grafting is a valuable tool in tomato production but its potential could go unrealized in soils that are healthy and free of soil-borne diseases. Benefits in healthy soils could exist depending on rootstock types. Alternatives to the rootstock we examined should be utilized, and localized grafting trials should be continued to provide clearer answers for Midwest high tunnel tomato production.