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United States Department of Agriculture

Agricultural Research Service

Research Project: VEGETABLE GRAFTING FOR RESISTANCE TO SOILBORNE DISEASES

Location: Subtropical Plant Pathology Research

2013 Annual Report


1a.Objectives (from AD-416):
Obj. 1: Identify available germplasm resistant to soilborne diseases and pests currently being controlled by pre-plant soil fumigation with methyl bromide for use as grafting rootstocks for Solanaceous vegetables, primarily tomato and pepper. Obj. 2: For selected rootstock germplasm shown to be effective for management of soilborne pests and pathogens of economic importance in the southeastern United States, describe rootstock-scion interactions that influence plant growth, fruit yield, fruit quality, and other important horticultural traits. Obj. 3: For selected rootstock-scion combinations shown to have an acceptable resistance to soilborne pests and pathogens and produce fruit of acceptable quality, evaluate under field conditions, similar to those used for commercial production, the plant growth, fruit yield, fruit quality, and other important horticultural traits that contribute to the economic feasibility of grafting.


1b.Approach (from AD-416):
Identify rootstock and scion germplasm material which have traits that resist diseases commonly found in the Southeastern U.S. currently controlled by methyl bromide. Screen available rootstock material for compatibility using current and new techniques. Select and evaluate rootstock and scion combinations for initial disease resistance and adaptation to current and new cultural technique. Determine the influence of rootstock/scion combinations on the horticultural characteristics of fruit including fruit appearance pre and post harvest quality, flavor, time to maturity, and yield. Develop techniques to evaluate the growth and development of the plant combinations under biotic and abiotic stress and evaluate grafted plant performance under varying cultural conditions.


3.Progress Report:
Two tomato grafting field trials were conducted over the 2012/2013 tomato growing season in the southeastern Florida production region. Trial 1 was in cooperation with Alderman Farms on their 300 acre organic farm in Loxahatchee, Florida. Trial 2 was in cooperation with Big Red Tomato Packers and Diamond Tomato Partnership on their 450 acre conventional farm in Fort Pierce, Florida. Tomato transplants for both trials were grown and grafted at the US Horticultural Research Laboratory in Fort Pierce, FL. Both trials were harvested and graded by the commercial grower to ensure that pack-out and marketable yield data was truly representative of a commercial production scenario. To facilitate grading of harvested fruit by the grower, each rootstock/scion combination was planted in one large plot without replications.

The performance of individual rootstocks varied depending upon the scion used and the location of the trial. For example, at the organic farm, 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 the organic location but was one of the lowest producing rootstocks at the conventional location. The results indicate that under commercial tomato production scenarios, yields of various rootstock/scion combinations can vary from farm to farm and season to season.

Trial 1- Organic Farm: Seedlings were planted between August 13 to 21 into individual cells of plastic seedling trays (288 cells per tray). Seedlings were grafted between September 7 to 12. Grafting was accomplished by clipping the scions at the soil level and the rootstock below the cotyledon. Cuts were made at a 70 degree angle. Scions and rootstocks were placed into the appropriately sized grafting clip so that their cut edges were joined together. Grafting seedlings were placed in a growth chamber with 100% humidity for 7 to 10 days. All grafted seedlings were transplanted into the field on October 22. Large, single row plots were used to facilitate grower harvesting and collection of pack-out data. Plots were harvested on January 25 and February 4, 2013. Fruit was sorted based on quality but was not sized. Plots were surveyed for the incidence of plant disease (Fusarium wilt, Fusarium crown rot, and Sclerotium rolfsii) and severity of root galling by Meloidogyne species at the second harvest. Disease incidence and severity of root galling were less than 1% for all rootstock/scion combinations.


Last Modified: 10/1/2014
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