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United States Department of Agriculture

Agricultural Research Service

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Location: Vegetable Crops Research

2013 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, 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.

3. Progress Report:
This project was renumbered from 3655-21000-048-17A to 3655-21000-062-05A. This is the final report, project terminated 08/31/2013. Root-knot nematode resistance screening trials were conducted in the California main carrot seasons in both 2012 and 2013. In each season, field trials were conducted on two sites, one infested with M. incognita and one with M. javanica. The 2012 trials were at the University of California (UC) South Coast Research Center, Tustin, CA, and in 2013 at the UC Kearney Research Center, Parlier, CA. On each field site and year, several hundred selected advanced and early generation carrot lines were grown in plots adjacent to susceptible control plots. The 2012 data allowed for selection of numerous advanced lines with dual resistance to the two root-knot nematode species. Selected plant taproots were shipped to Wisconsin for further advancement and for use in crossing. The lines were also evaluated for agronomic characters including root shape and color. The best lines were put into a seed increase effort for future testing and sharing with seed industry breeders. At UC Riverside, a series of greenhouse based screens for carrot resistance to M. incognita and M. javanica were conducted in controlled pot tests. Results from these tests were used to validate field screening results and also for detailed assays of nematode resistance inheritance in segregating progenies generated from crosses between parents carrying different sources of nematode resistance. Results of the field and greenhouse screenings in 2012 were presented in the California Fresh Carrot Advisory Board Annual report and at the California Carrot Industry symposium in March 2013. A field day was held in November 2012 at the Tustin field sites during the carrot line evaluations. The field day was attended by representatives of the major carrot processing companies and carrot breeders from the primary carrot seed production companies. The field trials in 2013 were planted in May and current growth is excellent. The lines being screened represent confirmatory tests of the best lines from 2012, plus sets of new lines generated from selfing and crossing among previous selections. The lines will be evaluated for nematode resistance in September 2013, at which time an industry field day will be held, and the results shared with the carrot industry through their annual report and carrot symposium. In September 2012, a commercial field experiment was established to test two resistant hybrid lines with strong nematode resistance and standard susceptible commercial line, as part of the nematode resistance implementation effort. Large-scale seed lots (about 4kg) of these advanced nematode resistant carrot lines were developed with seed industry partners for the large-scale evaluation trial. The trial was designed with pre-plant fumigated and non-fumigated split plots. Unfortunately, the trial was harvested in error by the grower contractor before the yield and processing assessments could be made. Attempts are underway to repeat this commercial scale test in 2013 using residual large-scale seed lots. This research relates to Objective 1, Determine the genetic basis of and initiate selection for carrot, onion, cucumber, and melon quality attributes influencing human nutrition and health, disease resistances, and yield and quality components, and stress tolerance in cucurbits, and perform field performance and quality trials and Objective 2, Utilize current biotechnology to discover and evaluate genetic variation and to map agriculturally important traits in Allium, Cucurbit, and Daucus germplasm, and to develop genetic and breeding stocks, by evaluating nematode resistance in carrot stocks to be deployed.

4. Accomplishments

Last Modified: 10/16/2017
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