Verticillium Wilt Management: Elucidating Mechanisms of Resistance and Integration of Sustainable Alternatives in Tomato Production Systems

Project Overview

GS11-102
Project Type: Graduate Student
Funds awarded in 2011: $9,970.00
Projected End Date: 12/31/2013
Grant Recipient: North Carolina State University
Region: Southern
State: North Carolina
Graduate Student:
Major Professor:
Dr. Frank Louws
North Carolina State University

Annual Reports

Commodities

  • Vegetables: tomatoes

Practices

  • Education and Training: participatory research
  • Pest Management: genetic resistance, integrated pest management

    Abstract:

    Graftingwith various rootstocksis an IPM tool that can provide protection againstsoilbornediseases,and previous studies have documented the successofgraftingto manage bacterial wilt, Fusarium wilt, Southern stem blight and root knotnematodesin fresh market tomato production in North Carolina. In this threeyear study, multiple rootstocks were evaluatedcompared to standardfumigation methods to assess theirefficacyagainstVerticillium wilt, caused by the soilborne fungus Verticillium dahliae. There is no known resistance to the race 2 form of this pathogen, the most prevalent strain in the mountain production region, but in this thesis we hypothesized vigorous rootstocks may confer tolerance to the pathogen. In the absence ofVerticilliumwilt pressureduringtwo ofthe study years,graftingmethods did not affect plant growth oryield when compared to non-grafted control and fumigation treatments. In the third year and in the presenceof Verticillium wilt, rootstocks OH316 and Maxifort providedthe best control againstthe pathogenwhile stilldelivering similaryields as the non-graftedplants in fumigated plots. Rootstocks OH313 and a Japaneseline ‘Aibou’did nottolerate Verticillium wilt pressure as wellasOH316, Maxifort, and thenon-grafted control, which resulted in lower fruityields. Grafting can play an important role in future IPM programs to reduce losses due to this important pathogen especially in high value tomato crops that can compensate for the extra costs of grafted plants.

    Introduction

    The purpose of this project is to determine the potential benefits of using grafted tomato plants to manage the disease Verticillium wilt in tomato production. Tomatoes are the fourth most popular fresh vegetable in the USA and North Carolina is one of the top fresh market tomato producers {USDA 2009} and has a farm gate value of $33.7 million to the state economy {NCMarketReady 2008}. Unfortunately, there are many different diseases that limit production. One of the more serious diseases is Verticillium wilt (VW) caused by the pathogen Verticillium dahliae. V. dahliae is a soilborne vascular pathogen that enters the host through the roots and colonizes the xylem tissue through the formation of conidia leading to plant stunting, wilt and ultimately plant death.   In conventional systems, the method of choice for controlling V. dahliae is to use fumigants to reduce the inoculum load in the soil before planting. However, with the phase-out of methyl bromide as a soil fumigant and increased interest in organic production in the state, new methods are needed to manage this serious pathogen. Grafting is a potential viable solution to this problem within an IPM framework. Grafting is used extensively in many parts of the world to manage soilborne diseases and reduce abiotic stress, such as salt tolerance, and to increase yields and fruit quality. A major benefit of grafting is that a grower can produce tomatoes (scion) that meet local or regional market demands but select rootstocks that offer site-specific benefits such as resistance to know pathogens on the farm. A major challenge tomato growers face in the mountain production region is that resistance is available to the race 1 strain of the pathogen but no resistance is known worldwide to the race 2 form of the pathogen, the predominant strain in the mountains. Therefore, many growers can suffer serious losses in yield. In this work, we hypothesized that rootstocks that confer plant growth vigor to the scion may reduce crop losses growers experience due to VW pressure. A series of field experiments and lab experiments were conducted to advance our knowledge about the utility of grafting to manage the race 2 strain of V. dahliae.

    Project objectives:

    The objectives of this work were to:

    1) Evaluate the utility of rootstocks as a viable mechanism for growers to manage Verticillium wilt in fumigated and non-fumigated soils.

    2) Advance our knowledge about mechanisms of host resistance through intensive field sampling, PCR analysis and greenhouse assays;

    3) Communicate results to growers and other clientele with recommendations of designing integrated and sustainable tomato production systems.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.