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United States Department of Agriculture

Agricultural Research Service

Related Topics


Location: Vegetable Crops Research

2011 Annual Report

1a. Objectives (from AD-416)
Deployment of nematode resistant carrots to U.S. growers and seed industry.

1b. Approach (from AD-416)
We have discovered multiple genetic sources of nematode resistance in carrot germplasm. In this project we will confirm the strength of the resistance in cooperation with University of California nematologists, intercross best resistance, produce ample seed for extensive field testing, and release best resistance to the public, especially growers and seed companies. We will also evaluate horticultural quality including field performance traits (color, shape, uniformity) and consumer quality (flavor and nutritional value), hold field days for the carrot production community, and confirm genetic models of resistance in mapping populations. Specialty Crops Research Initiative.

3. Progress Report
Carrots are an important source of nutrients for the United States (U.S.) diet and have $550 million farm gate value to U.S. growers, but root-knot nematodes (Meloidogyne spp.) threaten approximately 3/4 of the U.S. carrot crop. Nematode infection causes forking and galling disfiguration to carrot taproots resulting in ‘cosmetic injury’ and economic loss. New sources of genetic resistance have been identified in several unrelated germplasm sources from carrots of diverse geographic origins including Brazil, Europe, Syria, China, and Australia. Inbred lines, single cross hybrids and diverse populations from several sources of resistance have been developed and evaluated on a small scale in field test sites heavily infested with nematodes. These sources of nematode resistance vary widely in nutritional value attributable to both carotenoid and anthocyanin pigments and also vary in flavor. Root-knot nematodes cause significant levels of economic loss for U.S. carrot growers. Inbred lines, single cross hybrids, and diverse populations from several sources of resistance have been developed and evaluated on a small scale in field test sites heavily infested with nematodes. Plants with superior levels of resistance have been selected and seed supplies of selected individual plants were increased in collaboration with industry cooperators to provide adequate seed for larger scale testing in the upcoming year. Advanced Brazilian and Syrian resistance sources are in seed production trials to increase seed quantities to a level adequate to allow medium-scale field testing of resistance on grower fields within a year. Seed companies, and both large and small-scale growers, are involved in testing these improved carrot populations and hybrids. A website was developed to target large and small-scale carrot growers, and regular interactions with crop production and seed production industry personnel provide stakeholder input as a part of this project. Collaborative trials in organic production sites are underway. Regular communications have been established with carrot growers and seed company representatives on our industry stakeholder team, as well as with other carrot growers and seed companies. This project is moving nematode resistant carrots into mainstream production and also improving nutritional value of typical orange, nematode resistant carrots. The inheritance and genetic map location of resistance genes is being determined, and molecular markers are being developed to facilitate incorporation of resistance genes by indirect selection. Carrot types with unusual purple and yellow colored taproots that occur in resistant germplasm will also be available for large-scale and niche market growers. Nutritional quality and flavor were evaluated and promising breeding stocks are evident. Results will demonstrate the genetic basis of nematode resistances in carrot and provide nutritious nematode resistant carrot germplasm for producers. Project monitored by regular meetings and e-mail discussions of progress.

4. Accomplishments

Last Modified: 10/20/2017
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