Location, Cropping System, and Genetic Background Influence Carrot Performance, Including Top Height and Flavor, in the CIOA (Carrot Improvement for Organic Agriculture) Project

U.S. organic farmers surveyed listed improved seedling germination and Alternaria leaf blight resistance as top breeding priorities for field production of organic carrots. Nematode resistance is also very important for growers. Flavor was deemed the most important consumer trait to improve in carrots, and nutrition the most important product quality variable for consumers. To address these needs, field trials of 34 diverse carrots varying in top size, disease and pest resistance, root shape and color, flavor, and nutritional value were evaluated by the Carrot Improvement for Organic Agriculture (CIOA) Project on both organic and conventional farms in California, Indiana, Washington, and Wisconsin. Wide ranges of seedling growth rates and canopy sizes were observed in this diverse carrot germplasm that includes not only orange carrots, but also novel purple, yellow, and red storage root colors. Top height varied two-fold among entries at a given location, and fresh carrot flavor (sweetness and harsh, turpentiney flavor) varied widely among the genetic stocks evaluated across the locations and production systems. Relative top height ranking among genetic stocks was consistent with no system-by-variety interaction detected for this trait. Relative ranking of flavor scores was also relatively consistent across locations. Soil assays comparing the organic and conventional trials at each site indicated significant differences among locations, and between organic vs. conventional paired trials in all four locations, including labile organic matter pools, and bacterial, fungal and archaeal community composition. To evaluate root-knot nematode resistance, select material was planted in a trial on nematode infested ground at the University of California South Coast Research & Extension Center. Leaf blight resistance was evaluated in trials at the University of Wisconsin Hancock Experiment Station. Nematode and Alternaria leaf blight resistance trials demonstrated a wide range of variation among genetic stocks.  Other diseases observed in some of the trials were bacterial blight, Cercospora leaf spot, and powdery mildew. A brochure was prepared and distributed, and a web site was developed through eOrganic (http://eorganic.info/carrotimprovement) to inform growers, the carrot industry, researchers, and consumers about the project, including trial results. The CIOA Project reached approximately 60 farmers in 2012 with education on organic breeding and variety trials. This project has a diverse advisory panel, and is creating a model for farmer-researcher participation in breeding, seed production and evaluation programs for organic systems.