Location: Crop Improvement and Protection Research
Project Number: 2038-22000-019-054-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Feb 1, 2024
End Date: Jan 31, 2025
Objective:
1. Validate race-specific molecular markers to detect California Fusarium oxysporum f. sp. fragariae race 2.
2. Conduct surveillance for California Fusarium oxysporum f. sp. fragariae race 2 in strawberry fields.
3. Aerial dispersal of Fusarium oxysporum f. sp. fragariae - Determine the infective potential of aerial spores of Fusarium oxysporum f. sp. fragariae.
4. Screen wild and heirloom strawberry varieties for resistance to California Fusarium oxysporum f. sp. fragariae race 2.
Approach:
1. We will continue validation of California Fusarium oxysporum f. sp. fragariae race 2 molecular markers by testing plant samples that are displaying wilt symptoms for this pathogen. We will compare the results from our recombinase polymerase assay with those obtained through traditional plating methods.
2. We will continue pro-active and systematic sampling of strawberry fields and testing the collected samples for California Fusarium oxysporum f. sp. fragariae race 2. We will also use genomics to retrace route of dispersal by identifying relationships between isolates at different fields in the Oxnard area. Fields whose populations of this pathogen are more closely related to each other may have had more recent spread. This will identify common links between fields that can be used to determine routes of dispersal and potential other fields that should be sampled.
3. Past research has shown that Fusarium oxysporum f. sp. radices-lycopersici and f. sp. basilici can initiate foliar infections of their preferred host. It is unknown whether the airborne conidia produced by F. oxysporum f. sp. fragariae also cause above-ground infections on strawberry plants. To assess this capability, conidia produced by F. oxysporum f. sp. fragariae sporodochia will be mechanically transferred to wounded and unwounded leaves, petioles, and crowns of healthy strawberry plants. Destructive sampling followed by surface disinfestation and plating on selective media will be used to identify infected tissues and quantify the rate of spread from inoculated surfaces. Some plants will remain unsampled for a period of 12 weeks (or longer, if necessary) to determine if wilt symptoms can be caused by above-ground infections. These experiments will determine the potential for airborne conidia produced by F. oxysporum f. sp. fragariae to initiate a polycyclic spread of Fusarium wilt.
4. Wild and heirloom varieties of strawberry will be root-dip inoculated with a concentrated suspension of California Fusarium oxysporum f. sp. fragariae race 2 spores. Plants will be grown in a controlled environment for eight weeks and symptoms recorded on a weekly basis. Varieties that show no symptoms by the end of the experiment will be investigated for resistance in subsequent trials.
