2010 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 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 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. 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. Mapping of resistance has preliminarily indicated an independent genetic origin of resistance to M. javanica derived from Asian germplasm, and additional resistance from wild European carrot is in progress. Plants with superior levels of resistance have been selected and seed supplies of selected individual plants with elite high resistance are being increased for testing in trials in the upcoming year. A web site is being developed to target large and small-scale carrot growers (http://www.ars.usda.gov/pandp/docs.htm?docid=19858 ) as a part of this project. 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.