Grafting heirloom tomatoes for organic high tunnel production to improve season extension, disease control, and fruit yield: A partnership with local growers for technology transfer

Grafting heirloom tomatoes for organic high tunnel production to improve season extension, disease control, and fruit yield: A partnership with local growers for technology transfer

Summary

An experiment comparing grafted and non-grafted specialty tomatoes for soil-borne disease resistance, yield, and fruit quality was conducted at the Frog Song Organics farm, Hawthorne, FL. Four indeterminate, small-fruited cultivars selected by the grower were used, including ‘Black Cherry’, ‘Green Zebra’, ‘Supersweet 100’, and ‘Sun Gold’. They were grafted onto two commercial tomato rootstocks ‘Multifort’ and ‘Estamino’, with the non-grafted tomato scion cultivars as the control. Grafting was shown to be an effective tool for managing Fusarium wilt. Total marketable yield was significantly higher in grafted vs. non-grafted plants. Some scion-rootstock interaction effects were observed in fruit quality assessment.

Objectives/Performance Targets

Objective 1. Determine the effectiveness of grafting with resistant rootstocks for controlling soil-borne diseases in heirloom and specialty tomatoes grown in organically managed high tunnel. 

Objective 2. Assess fruit yield and quality as affected by grafting with vigorous disease-resistant rootstocks. 

Objective 3. Analyze the costs and returns of high tunnel production of grafted tomatoes to determine its economic feasibility in a commercial operation setting.

Accomplishments/Milestones

The experiment was carried out in an organically managed high tunnel (22 ft by 88 ft) at Frog Song Organics, a certified organic farm in Hawthorne, FL. Four indeterminate, small-fruited specialty tomato cultivars selected by the grower, including ‘Black Cherry’, ‘Green Zebra’, ‘Sun Gold’, and ‘Supersweet 100’, were grafted onto two commercially available rootstocks ‘Multifort’ and ‘Estamino’. The non-grafted tomato scion cultivars were used as the control. A randomized complete block design was used with 3 replications and 5 plants in each plot. Tomato transplants were planted in December 2014. Plants were managed following production methods used by the grower. First harvest began on March 17, 2015 and was continued 2-3 times per week until June 2015. Fusarium wilt and leaf mold were identified as the main soil-borne and foliar diseases, respectively. Marketable and unmarketable fruit weight and number were measured at each harvest. Aboveground plant biomass was also measured after the final harvest. Representative fruit samples were collected for fruit quality assessment including soluble solids content, titratable acidity, and pH. Grafting with the two rootstocks was shown to be highly effective in managing Fusarium wilt and improving marketable fruit yield. Interestingly, grafted plants also showed less severe symptoms of leaf mold in comparison with non-grafted plants. The yield increase in grafted plants primarily occurred in May and June. Grafted plants had significantly higher aboveground biomass than the non-grafted plants at the end of the production season. Grafting did not exhibit any significant impacts on titratable acid and pH of tomato fruit, while some scion-rootstock interactions were observed with respect to soluble solids content. Partial budget analysis demonstrated a marked increase in partial net return by using grafted tomato plants as compared to non-grafted tomato production.

Impacts and Contributions/Outcomes

This trial was a successful demonstration of how grafting with resistant and vigorous rootstocks can effectively control soil-borne diseases and improve tomato yield and economic returns. In the intensively managed organic high tunnel system, using grafted plants also allowed flexibility in crop and cultivar selection and rotation. Prior to this on-farm study, the grower had a complete crop failure with ‘Black Cherry’, a popular tomato cultivar in the local market, under high tunnel production due to the high pressure of Fusarium wilt. At the end of the study, the grower was convinced that grafting can be used as an economically viable tool to help him solve site-specific soil-borne disease problems. He was even considering using grafted plants for open-field production of tomatoes at the farm. Results from the on-farm trial were presented at the National Vegetable Grafting Symposium in December 2015.

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