Location: Temperate Tree Fruit and Vegetable Research
Project Number: 2092-21220-003-023-T
Project Type: Trust Fund Cooperative Agreement
Start Date: May 1, 2021
End Date: Jun 30, 2024
Objective:
1. Objective 1: Analyze psyllids of multiple species collected from potato fields and neighboring weedy plants in Oregon’s Klamath Basin and Washington’s Columbia Basin for the presence of Lso.
1. Objective 2: Start and maintain a colony of Lso-infected Aphalaridae psyllids.
2. Objective 1: Complete a molecular analysis of the P. allius and TRV populations to determine if there are genetic differences between the 2019 field isolate and the isolate present in the USDA-ARS disease field.
2. Objective 2: Determine if TRV infection on a single root moves systemically throughout the entire root system.
2. Objective 3: Determine if depletion of P. allius populations will prevent further CRS symptom development in tubers (without use of specific chemistries).
2. Objective 4: Compare the growth rate and quality of plants generated from TRV-infected and TRV-uninfected seed in field conditions, with or without fumigation.
3. Sole ARS Objective: Potato Psyllid and Plant Testing for Candidatus Liberibacter solanacearum
Approach:
1: Obj 1. Sticky cards from potato fields in the Klamath and Columbia Basins will be received and psyllids identified to species when possible. All psyllids will be subjected to nucleic acid extraction and analyzed for the presence of Lso. Lso-positive psyllid samples will be subjected to in-depth analysis of Lso haplotype. PCR products will be cloned, sent in for sequencing, and results analyzed by comparison to all Lso haplotypes. Psyllid species will be identified to the extent possible by molecular techniques targeting the CO1 barcoding gene. Obj 2: Weeds and other non-crop plants in the Klamath and Columbia Basins will be sampled for psyllids. Psyllid specimens will then be identified to the species level when possible and live specimens will be released in cages containing rumex or polygonum plants and allowed to establish a colony. After successful colony development, adult psyllids will be removed and tested for the presence of Lso.
2: Obj 1: P. allius populations will be compared by molecular assays that target three different “barcoding” genes that will collaboratively identify any variation in nematode populations. Obj 2: Using the same ‘split-pot’ design used in year one of this study, we will assess if P. allius feeding on a subset of potato roots can cause TRV to move systemically throughout the root system. At 8 and 12 weeks following inoculation with TRV-infected P. allius, leaf tissue, crown tissue, root tissue, and tubers will be isolated from each plant or pot and assayed for presence of TRV. Tubers will be assessed for CRS symptoms. Soil from each pot will also be assessed for presence of P. allius. Obj 3: A trial will be repeated in year 2 to compare CRS symptom development between tubers produced under continual TRV-infected P. allius pressure and those produced after pressure has been removed. TRV-infected and un-infected seed pieces will be planted in soil containing TRV-infected P. allius, and following 2, 4, or 8 weeks of feeding, plants will be removed from the soil, roots will be washed in a bleach solution and plants will be repotted in clean nematode-free soil. At harvest, roots and tubers will be assessed for TRV expression and CRS symptom development. Obj 4: We will complete a larger field trial to compare plant emergence, growth rate, and stem properties from TRV-infected and -noninfected seed pieces planted under both fumigated and non-fumigated field conditions. Emergence data and foliar vigor will be estimated and individual plants from each of the treatments will be excavated and their underground stem tissue will be examined for symptoms of distortion and mottled coloring.
3: All potato psyllids collected from sticky cards will be tested to determine if they are infected with Lso. The first ten potato psyllids collected in a field each week will be tested individually, and any additional psyllids will be bulked up to 30 per tube and tested as a group. As an alternative, a high-throughput method of extraction is currently being designed and optimized to increase the number of samples processed in a week. Upon proper validation, this method may be ready for implementation in 2021.
