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Grafting Tomatoes to Enhance Disease Resistance

Tomato producers face challenges from numerous disease causing organisms. Commercial producers of field grown tomatoes rely on a combination of resistant varieties, rotation and soil fumigation to limit damage from soil pathogens such as nematodes, Fusarium wilt, Verticillium wilt and bacterial wilt. The phase out of methyl bromide for soil fumigation has increased demand for alternative options. Fresh market tomato producers are experiencing increased demand for heirloom tomato varieties. Most heirloom varieties are indeterminate and not well suited for commercial plasticulture. In addition, most heirloom varieties lack the genetic disease resistance that has been incorporated into modern commercial varieties. However, these tomatoes come in a variety of colors, sizes, and flavors that make them highly desirable. They often sell for two to three times the price of other varieties. Greenhouse and high tunnel tomato producers have limited production options in regard to suitable varieties, fumigation and the ability to rotate crops.

Grafting has been used to enhance the productivity of woody species for centuries. Grafting for vegetable production is a more recent development but increasingly important. With the phase out of methyl bromide the use of grafted tomatoes, melons and cucurbits have become a standard IPM practice in Southeast Asia, Japan and countries in the Mediterranean region. The use of grafted plants has also become standard practice in greenhouse tomato production. Alabama vegetable growers and Alabama Cooperative Extension System (ACES) agents are not generally familiar with the practice, production and use of grafted tomato plants. The objective of this program was to introduce ACES agents and growers to this practice. Since there is not at this time a producer of grafted tomato plants in the United States, it was necessary to conduct training for ACES agents. In order to do this, Extension partnered with the Wallace State Community College Department of Agriculture Production and Horticulture who agreed to produce plants for grafting. With a grant from the Alabama IPM minigrants program, several grafting sessions were conducted in 2007 and 2008 for Alabama vegetable growers.

April 2007. During April of 2007 ACES agents and Wallace State educators conducted a grafting session at the Community College Greenhouses. Five varieties of heirloom tomatoes were grafted to ‘Maxifort” a disease resistant rootstock from deRuiter Seeds Company.

Overall successful grafts were achieved with 40% of the transplants. Experienced commercial grafters generally report success in the 90% range. Factors influencing graft success included: lack of experience in grafting tomatoes (None of the participants had previously grafted tomatoes), the size of the transplants (many plants were too large for the whip grafts and clips that were used), and possibly varietal differences. All tomato grafts were done the same day with the Cherokee Purple variety being grafted first and Momataro being grafted last. The percentage of plants successfully grafted increased from 19% to 68% as the grafters gained experience.

December 2007. As part of the Deep South Fruit and Vegetable Growers Conference in Mobile a workshop on “Grafting Heirloom Tomatoes to Increase Disease Resistance” was held. A total of 44 producers, extension agents and extension faculty were given hands on instruction on grafting tomatoes. A powerpoint presentation was developed and educational bulletins from North Carolina were distributed to attendees.

March 2008. A workshop on “Grafting Tomatoes for Disease Resistance” was conducted at the 2008 Greenhouse Tomato Short Course in Jackson, Mississippi. Forty growers from eight states participated.

 

Potential benefits of using grafted tomatoes include the elimination of methyl bromide for fumigation of soil pathogens, compatibility of grafting with organic/sustainable growing systems, increased per plant yields, lower nutrient requirements on a per acre basis, better disease management in greenhouse and high tunnel plantings and the ability to grow heirloom varieties that offer growers better profits. Offsetting these benefits are the increased costs of producing grafted plants, the increased amount of time needed for producing grafted plants and the lack of variety of cultural management information needed to optimize production with grafted plants. On balance the use of grafted plants can be lower than that for nongrafted plants since fewer plants and lower chemical inputs are needed to achieve yields similar to those of nongrafted plants.

Improving the Cost/Benefit Ratio of IPM

For More Information, Contact:
Stan Roark
Regional Extension Agent
PO Box 227
Wedowee AL 36278
256 357-2841

Email: roarkrs@aces.edu


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