Inducing Disease Resistance and Increased Production in Organic Heirloom Tomato Production Through Grafting

View the project final report

• 2005 annual report
• 2006 annual report
• 2007 annual report

Commodities

• Vegetables: tomatoes

Practices

• Crop Production: application rate management
• Education and Training: demonstration, display, extension, on-farm/ranch research, participatory research, technical assistance, workshop
• Farm Business Management: marketing management, value added
• Pest Management: cultural control, genetic resistance, integrated pest management
• Production Systems: transitioning to organic
• Sustainable Communities: new business opportunities, sustainability measures

Fruit-bearing vegetable crops have been cultivated with grafted plants worldwide. However, this technique is relatively unknown in the United States. The use of tube grafting in Korea and Japan has made this technology practical for managing soilborne diseases in many crops including melons, cucurbits, eggplant, and tomatoes. Soilborne diseases in the southeastern United States are a major limitation to crop productivity, especially for organic farmers where fumigants are not available. In our initial work, we will focus on bacterial wilt of tomato, a problematic disease for many farms in the southeast. Resistant lines have been identified, but their fruit quality is often poor. Furthermore, there is no resistance to this disease in heirloom varieties of tomatoes, which are a major crop for small, sustainable farmers in North Carolina. This project will evaluate the use of grafted tomato plants in order to make an effort to reduce bacterial wilt incidence in the field. Furthermore, field trials will determine if grafted tomatoes will increase productivity in the presence and absence of disease. In addition, we will conduct more basic research on the physiological defense signaling mechanisms to determine how resistance is affected in the field. Finally, an active outreach program will be developed in order to convey the findings and importance of this study to NC farmers. The use of grafted tomato transplants may be a viable tool for organic growers, who encounter soilborne disease problems, and may be useful to conventional growers as a sustainable alternative to chemical treatments.

The objectives of this project are three-fold:
1) An evaluation of rootstock/scion combinations will be carried out in North Carolina through field trials as well as greenhouse trials. Grafted heirloom tomatoes have been planted in the field where bacterial wilt incidence is historically high. Data will be collected pertaining to disease incidence as well as yield and fruit quality. Furthermore, production techniques will be analyzed in an effort to increase yield on a per-plant basis, thereby offsetting the added cost of using grafted transplants. The expected outcomes of this aspect are increased disease resistance in areas where bacterial wilt pressure is high and increased productivity even in the absence of disease. The practical application of this technique and its success will be evaluated and manipulated in order to cater to the success of North Carolina farmers.
2) To determine the efficacy of induced resistance mechanisms when heirloom scion are grafted onto resistant rootstocks. Many of the signaling systems that occur in tomatoes are based around hormones and other compounds that are produced in the roots. This idea may have significant impacts on the ability of specialized rootstocks to induce resistance to foliar diseases in the future. This project is an outstanding candidate for this type of research as the tomato has been used as a model for both the Systemic Acquired Resistance and Induced Systemic Resistance mechanisms. Therefore, many of the physiological mechanisms that are required for this type of inquiry have been previously characterized. We hypothesize, that by understanding how a grafted plant communicates the expression of certain genes throughout its entirety, we may be able to better identify the mechanisms which lead to resistance. This work will lead to a knowledge base to direct this technology through breeding and other cultural techniques.
3) To communicate the results and ideas behind this research through extension and education. An active role will be taken in an effort to introduce farmers as well as extension agents to this technology. Demonstration plots will be used to illustrate the benefits of grafting directly. Grower workshops and training seminars will be conducted in order to show farmers how to graft their own transplants. Finally, we will construct extension publications that describe both the grafting technique and identify resistant lines suitable for rootstock. As this technology is relatively unknown in the United States, it is fundamental that the results of this research are made available through grower workshops and publications.