Location: Crop Improvement and Protection Research
Project Number: 2038-21530-003-017-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Oct 1, 2023
End Date: Sep 30, 2024
Objective:
The main purpose of the research in this proposal is to develop celery germplasm resistant to Fusarium wilt, caused by Fusarium oxysporum f. sp. apii (Foa) race 2 and race 4 for release to celery breeders. Foa race 2 continues to be a problem for celery growers in Ventura, San Luis Obispo, and Monterey counties. The highly virulent strain Foa race 4 has been described as a “death sentence” by growers in Ventura county, though the pathogen is not yet prevalent in all growing areas. Continued breeding, testing, and selection for stacked resistance again Foa race 2 and 4 in celery is of the utmost importance because host resistance is the best method of sustainable control of the different host-specific strains of Fusarium oxysporum in multiple crops.
Specific objectives:
1. Continue development of UC Davis resistant germplasm lines for confirmation of field resistance and fixation of true celery morphology.
2. Development of new resistant germplasm lines to expand the genetic pool of resistant germplasm.
3. Evaluate existing and new germplasm lines and additional material in the field.
4. Evaluate performance of a susceptible cultivar under micronutrient amendments.
Approach:
1. UC Davis resistant germplasm will be tested in Foa race 4 infested fields, and selections will be made for resistant material with true celery morphology. UC Davis resistant germplasm will also be back-crossed to OP celery cultivars to improve celery morphology.
2. In previous years, crosses were made between OP celery cultivars with Foa race 2 resistance and OP heirloom and smallage celery accessions. Seed from these lines will be evaluated in Foa race 4 infested fields, and selections will be made for resistant material with true celery morphology.
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 in collaboration with UCCE San Luis Obispo, Ventura, and Riverside faculty. New and existing germplasm from private breeding companies will be solicited in January, and seed will be shipped to a cooperating transplant production nursery to develop transplants. Transplants will be delivered to the field at an agreed-on date, and a field crew provided by the nursery will assist planting. There will be 7-8 beds, containing 20 ft plots. Treatments will be new and existing germplasm from private breeding companies and USDA germplasm lines, and these will be randomized within 4 replicate blocks. 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.
4. As part of the field trials described for the approach for Objective 3 in Foa race 4 infested fields, we will test additional treatments of micronutrient amendments on a susceptible cultivar to understand if micronutrients and mineral nutrition can be used to mitigate the effects of disease pressure. Field trial design will be similar as the approach described above for Objective 3. Multiple micronutrient amendments will be applied by hand at agreed-on times, and plants will be evaluated for disease resistance and agronomic traits as described above.
