Location: Crop Improvement and Protection Research
Project Number: 2038-21530-003-026-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Oct 1, 2025
End Date: Sep 30, 2026
Objective:
The main purpose of the research in this proposal is to develop celery germplasm resistant to Fusarium wilt, caused by the soil pathogen Fusarium oxysporum f. sp. apii (FOA) race 2 and race 4 for release to celery breeders. FOA race 2 causes stunting, yellowing, and complete crop loss during cool weather in Ventura, San Luis Obispo, and Monterey counties. FOA race 4 causes plant death and complete crop loss during warm weather in those regions, and has been described as a “death sentence” by growers. There are no effective treatments for the soil pathogen, and resistant varieties are the most effective means of continuing production in diseased fields. Continued breeding, testing, and selection for stacked resistance again FOA race 2 and 4 in celery is of the utmost importance.
Specific objectives:
1. Continue development of UCD resistant germplasm lines for improvement of true celery morphology in the field.
2. Screen new germplasm in the greenhouse for FOA4 resistance to identify new genetic sources of resistance to add to the breeding program.
3. Evaluate existing and new germplasm lines and additional material in the field.
Approach:
1. Selfed progeny derived from selections of UCD resistant germplasm in 2023 were tested in FOA race 2 and FOA race 4 fields in 2025, and further selections were made for resistant material with true celery morphology in 2025. Promising lines will be developed for seed increases. Selections will be selfed for further improvement of celery morphology in 2026.
2. We will screen new germplasm from multiple sources for FOA race 4 resistance in carefully controlled greenhouse assays.
3. We will conduct field trials in cooperating growers’ fields in Santa Maria under FOA race 2 pressure and in Camarillo under FOA race 4 pressure. The field will be maintained by the grower until harvest maturity, at which time USDA and UCCE faculty will evaluate for disease resistance using a 0-5 scoring system, and will evaluate for agronomic traits such as height, weight, bolting, ribbiness, color, pithiness, suckering, and mortality.