Integrated Use of Grafting Technology to Improve Disease Resistance, Yield and Fruit Quality in Organic Heirloom Tomato Production

Integrated Use of Grafting Technology to Improve Disease Resistance, Yield and Fruit Quality in Organic Heirloom Tomato Production

Summary

Grafted heirloom tomatoes showed improved root-knot nematode resistance as compared to nongrafted and self-grafted controls under organic production. Interestingly, there was no clear relationship between root galling and tomato yields. Moreover, the two heirloom tomato scions ‘Brandywine’ and ‘Flamme’ exhibited differential responses to the two rootstocks used in terms of yield performance. Fruit quality was generally not affected by grafting treatments. Economic analysis showed that grafting could be a cost effective solution to root-knot nematode control during the transition to organic production when high populations of nematodes are present.

Objectives/Performance Targets

Objective 1: Examine the effectiveness of using rootstocks in organic production of grafted heirloom tomato to provide resistance or tolerance to soilborne diseases and root-knot nematodes.

Objective 2: Assess growth promotion, yield increase, and fruit quality in grafted heirloom tomato production under organic growing conditions.

Objective 3: Analyze the costs and returns of producing and using grafted heirloom tomatoes in organic farming systems and provide updated information on the economic feasibility of adopting tomato grafting technology for these systems.

Accomplishments/Milestones

The heirloom tomato cultivars Brandywine and Flamme were grafted onto ‘Multifort’ and ‘Survivor’ rootstocks. Field trials were conducted in the spring season of 2011 at the University of Florida Plant Science Research and Education Unit in Citra, FL. In addition to the organic field trial, a trial was carried out on a site with a history of continuous nematode infestation that had been managed conventionally in previous years. The plants used in this trial were produced and grown following organic practices. This trial was designed to reflect growing conditions during a typical three-year transition period from conventional to organic production.

In both trials there were eight treatments consisting of nongrafted and self-grafted scions and the scion-rootstock combinations. A randomized complete block design was used with five replications.Fruit were harvested at the breaker stage of ripeness. Assessments of nematode infestation on plant roots were conducted after the final harvest. Total leaf area and above-ground biomass were also measured.

Consumer sensory analyses were conducted to assess the overall appearance, overall acceptability, firmness, tomato flavor, and sweetness of grafted and non-grafted heirloom tomato fruit. Fruit quality attributes including vitamin C, soluble solids content, pH, and total titratable acidity were also determined. In addition, cost of grafted heirloom tomato transplants was estimated. A sensory analysis was performed to compare the partial net return of nongrafted and grafted heirloom tomato production.

Impacts and Contributions/Outcomes

The results of this study demonstrated the effectiveness of using resistant rootstocks in root-knot nematode management in organic heirloom tomato production. Particularly under high pressure of root-knot nematode infestations, grafting may be an economically feasible pest control measure to help maintain a profitable production given that the risk of economic crop losses due to root-knot nematodes outweighed the higher cost of grafted transplants. When assessing whether or not to use grafted tomato plants for RKN management, growers need to consider the severity of the RKN infestation, the growing system, and the scion and rootstock cultivars to be used. Overall, grafting with disease resistant rootstocks did not show any consistent negative effect on tomato fruit quality attributes.

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