- Author: Laura J. Van der Staay
About 20 carrot industry stakeholders attended a carrot field day on October 7, 2015. The field day showcased the current status of a 20-year program to incorporate root-knot nematode resistance into commercial quality carrots. Philip A Roberts, Chair, nematologist, and professor in the Department of Nematology at UC Riverside, Philipp Simon, Carrot and Garlic Geneticist at USDA-ARS and the Department of Horticulture at University of Wisconsin, Madison lead the project. The research and breeding effort is funded by grants from the California Fresh Carrot Advisory Board and USDA-NIFA.
Numerous carrot advanced breeding lines show good resistance to root-knot infection and will be important in nematode management strategies when resistant varieties are released for growers. The project sites are infested with Meloidogyne javanica and M. incognita, the two common root-knot species in the warm interior valleys of California. To ensure uniform and heavily infested research sites, a 4-year rotation for experimentation (control and advanced selections and crosses of carrots) and uniform cropping (susceptible sorghum, lima beans, and tomatoes) is used.
Kearney is one of several sites used in field screening wild germplasm, new and advanced breeding lines, and finished varieties of carrots. The plots are coded for the source of resistance, and a highly susceptible carrot cultivar planted in every fifth plot is used to indicate the infestation levels. The primary goal is to select for resistance as well as market quality. The crossing of resistant and susceptible carrot lines is followed by agronomic and resistance selection to provide high quality resistant carrot breeding stocks to the seed industry. The seed companies then inter-breed the resistance with their own breeding lines to develop commercial varieties with resistance. The resistance should be highly beneficial for nematode management. Field site data is used with greenhouse data at UC Riverside. The project has also facilitated carrot genome mapping.