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United States Department of Agriculture

Agricultural Research Service

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Location: Citrus and Other Subtropical Products Research

2013 Annual Report

1a. Objectives (from AD-416):
1. To optimize grafting technologies to reduce costs of producing and distributing grafted seedlings and to make the technology readily available to U.S. open-field producers. 2. To integrate discovery-based, applied and on-farm research to optimize field production outcomes.

1b. Approach (from AD-416):
Growers of tomatoes and melons currently face many environmental, technical and market forces that demand innovative solutions to overcome constraints or to expand into emerging markets. For example, much of the fruiting vegetable industry, particularly in the southern production regions, has relied on fumigation as the primary soilborne pest management tactic. In contrast, emerging markets include extended season production using high tunnels, organic and specialty varieties, increased immigration, with an associated demand for fresh vegetables, and a general heightened awareness of health benefits with fresh vegetable consumption. Host genetics, if properly developed and deployed, offers sustainable mechanisms to manage soilborne pests and optimize productivity. By uncoupling root genetics from scion genetics through grafting, growers can produce superior varieties to meet market needs or rapidly adapt to new market conditions, yet choose site-specific rootstock solutions to soilborne pests and farming systems.

3. Progress Report:
This research is related to inhouse project objective: 4. Develop and evaluate grafting technologies (including determination of the soil pest complexes for which grafting is most suitable and development of tools to identify and avoid potential graft incompatibility issues) as management strategies for control of pests and pathogens currently or previously controlled by soil fumigants in vegetable cropping systems. The goal of this cooperative project is to mitigate limitations of grafted seedlings for U.S. open-field vegetable production to eliminate or reduce methyl bromide use for controlling soil-borne pests. During this reporting period experiments were conducted in Florida, in cooperation with commercial growers, including a field experiment evaluating grafted heirloom tomato production, performed in cooperation with an organic grower in St. Lucie County, FL, and a sustainable grower in Palm Beach County, FL. Two tomato field trials were also conducted in cooperation with an organic farm in Loxahatchee, Florida, and a conventional farm in Fort Pierce, Florida. Also, microplot, greenhouse, and growth chamber experiments were repeated to evaluate grafting techniques, virus resistance, and nematode susceptibility of both tomato and melon rootstocks. Data continues to be generated, collected, and analyzed for all experiments. Overall results for individual rootstocks varied depending upon the scion used and the location of the trial. At one organic farm, the heirloom tomato variety Purple Calabash had root-knot nematode galling on Matt’s Wild Cherry rootstock which was equivalent to galling of the non-grafted Purple Calabash plants, but when grafted onto Tygress rootstock galling and invasion by root-knot nematodes was significantly reduced. Galling by root-knot nematodes was higher on all ungrafted varieties. In organic and transitional vegetable production, there are few options available for virus management. Tomato yellow leaf curl virus (TYLCV) is a difficult problem for tomato growers and can completely devastate crops. Field and microplot trials were conducted to evaluate heirloom tomatoes used as scions grafted to the commercial cultivar 'Tygress'. Few studies have shown potential for management of viruses through the use of resistant rootstocks. Asymptomatic infection in some graft combinations was detected using tissue blot nucleic acid hybridization, which has been previously documented for TYLCV, and many grafted plants with severe symptoms showed virus infection of the tolerant Tygress rootstock. Results from work at another organic farm showed that marketable yield of Tribute grafted onto Multifort rootstock was 73% greater than FL-91 grafted onto the same rootstock. Cheong Gang was the highest producing rootstock at one organic location but was one of the lowest producing rootstocks at a conventional location. Under commercial tomato production scenarios, yields of various rootstock/scion combinations can vary among locations and growing seasons. Additional field trials are scheduled for fall 2013, in cooperation with organic and sustainable growers in St. Lucie and Palm Beach counties. USDA, ARS researchers are active in Executive and Advisory Team meetings, and commodity Working Groups. Numerous conference calls have been attended to coordinate Advisory Team, Executive Team, and Working Group activities, including a one day symposium and stakeholder workshop held in conjunction with the Annual Methyl Bromide Alternatives Conference, Orlando, FL, in which the ADODR was heavily involved. A second symposium and stakeholder workshop is being planned for the San Diego, CA Methyl Bromide Alternatives Conference in 2013, to engage U.S. West Coast growers interested in vegetable grafting. The ADODR is actively involved in this project, and coordinates with USDA, ARS team members.

4. Accomplishments

Last Modified: 06/25/2017
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