The 2010 ASHS Annual Conference

Carrots are an important source of nutrients for the 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 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 to the two most important root-knot species affecting carrot production, M. javanica and M. incognita, have been identified in several unrelated germplasm sources from local carrot populations 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.  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. Plants with superior levels of resistance have been selected and seed supplies of selected individual plants with elite high resistance were increased in collaboration with industry cooperators to provide adequate seed for larger scale testing in the upcoming year. 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.  Seed companies and both large-and small-scale growers are involved in testing these improved carrot populations and hybrids. A web site is being 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.