Location: Crop Improvement and Protection Research
Project Number: 2038-21530-003-007-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Oct 1, 2021
End Date: Dec 31, 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 4 and race 2 for release to celery breeders. This project is being handed from UC Davis to ARS, as the UC Davis Principal Investigator will retire and close their lab during the summer of 2022. 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 areas. Continued breeding, testing, and selection for Foa race 4 resistance 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. Previous breeding programs have resulted in celery germplasm with Foa race 2 resistance, but any Foa race 4-resistant germplasm must also be resistant to race 2 because of its prevalence in important celery growing areas.
Specific objectives:
1. To continue the UC Davis efforts to breed and select germplasm that has resistance and/or tolerance to Foa race 2 and 4 in order to distribute it to the celery-breeding community when the resistance genes are fixed or “breed true.”
2. To conduct field trials to screen for resistance to race 2 and race 4 among existing cultivars and new germplasm.
Approach:
1. Replication of the UC Davis Foa race 4 greenhouse assays at the USDA greenhouses in Salinas. Using protocols developed by UC Davis faculty and staff, we will repeat susceptibility assays in greenhouses using existing celery germplasm from private breeders and the USDA germplasm collection. The goal is to identify new potentially-resistant cultivars that have not yet been identified to use as parents to develop new resistant germplasm.
2. UC Davis has developed a Foa race 4 resistant germplasm to generation F1:4. Resistance is not yet fixed in that germplasm, that is, some progeny are still susceptible. For resistant plants in the F1:4 generation, we will vernalize the plants to induce bolting, and allow them to self-pollinate to produce an F1:5 generation. These seeds will be collected, germinated, and planted in cooperating growers’ field trials in Ventura county for continued evaluation.
3. There were additional F1:3 and F1:2 families that will be screened for resistance by UC Davis in the fall of 2021. After evaluation of the eight F1:3 and the five F1:2 families in UC Davis’ fall field trial, we will prepare any selected plants for vernalization and selfing to produce additional F1:4 and F1:3 families.
4. We will conduct field trials in the summer of 2022 in collaboration with scientists from UC Cooperative Extension San Luis Obispo county and UC Riverside. These trials will be under Foa race 2 pressure in cooperating growers fields in the Santa Maria area. We will screen existing germplasm, and germplasm developed by UC Davis with putative Foa race 4 resistance. This field trial will be harvested and evaluated for agronomic traits such as plant height/petiole length, average stalk weight, ribbiness, pithiness, bolting, foliage color, suckering, petiole cracking under Foa race 2 pressure in September, 2022. We will host a field day for the California Celery Research Advisory Board to evaluate the program.
5. We will conduct field trials in the fall of 2022 in collaboration with scientists from UCCE Ventura county and UC Riverside. These trials will be under Foa race 4 pressure in cooperating growers fields in the Camarillo area. We will screen existing germplasm, and germplasm developed by UC Davis with putative Foa race 4 resistance. This field trial will be harvested and evaluated for survival, but also agronomic traits such as plant height/petiole length, average stalk weight, ribbiness, pithiness, bolting, foliage color, suckering, petiole cracking under Foa race 4 pressure in November, 2022.
