Project Number: 2072-22000-046-037-I
Project Type: Interagency Reimbursable Agreement
Start Date: Oct 1, 2022
End Date: Sep 30, 2024
1. Compare graft indexing of Fragaria to RT-PCR and high throughput sequencing detection (HTS) methods for viral diseases. 2. Compare graft indexing of Rubus to RT-PCR and HTS methods for viral diseases. 3. Optimize and update virus detection protocols and provide recommendations to regulatory agencies on disease testing and quarantine time for Fragaria and Rubus, especially on the usefulness of graft indexing.
For Objective 1, symptomatic virus infected plants with single infection or mixed virus infections will be used and grafted onto each strawberry bioindicator lines UC 4, 5, 10 and 11 developed by the University of California strawberry breeding program. The Fragaria bioindicators are maintained by Foundation Plant Services (FPS) at UC Davis and initiated from virus-free tissue culture plants. After grafting, symptoms will be observed and recorded each week until dormancy. In addition, the 75 virus-infected plants will be tested by PCR and subjected to high throughput sequencing (HTS). For Objective 2, 75 known virus-infected Rubus plants (single and mixed infections) will be grafted onto Rubus occidentalis ‘Munger’. We use Munger as biological indicator for virus indexing of Rubus viruses including all types of raspberries, blackberries, salmonberry and thimbleberry. These 75 Rubus plants will be tested by PCR and HTS. RNA will be extracted from all infected plants using automated system to obtain consistent quality. All RT-PCR tests will be performed at the USDA virology lab and the HTS by the FPS, UC Davis. Results will be analyzed (objective 3) by in house bioinformatics tools.