Location: Genetic Improvement for Fruits & Vegetables Laboratory
Project Number: 8042-21000-305-013-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jul 1, 2022
End Date: Jun 30, 2025
Objective:
Novel and sustainable disease management tools are needed to mitigate the devastating economic impact common scab disease has for potato growers every year. An emerging strategy for the control of plant pathogens is immunity priming. This project will test the potential of priming the potato immune system using thiamin during exposure to the pathogen to attenuate common scab disease severity in the greenhouse and field. Thiamin may be a low cost, sustainable tool for the management of common scab and other pathogens of potato. The research plan is divided into three complementary objectives:
1. Determine efficacy of thiamin spray treatments for attenuating severity of common scab caused by four distinct species of phytopathogenic Streptomyces in a controlled greenhouse setting.
2. Determine efficacy of thiamin spray treatments managing common scab disease incidence and severity in Oregon fields with high common scab pressure.
3. Identify potato gene pathways activated by immune priming leading to differential pathogen response.
Approach:
1. Potato plants will be grown in pots inoculated with phytopathogenic Streptomyces and sprayed until leaf runoff 50 mM thiamin weekly. Each individual greenhouse experiment will include 54 pots (two treatment groups (mock vs. thiamin), two varieties (Purple Viking and Atlantic), two strains of the pathogen, six replicate pots for each strain-treatment-variety combination and six mock-inoculated check plants for both varieties). Across multiple experiments, four different strains of phytopathogenic Streptomyces will be tested in the greenhouse trials. At harvest, all tubers will be individually scored for disease severity based on percent of total lesion coverage and lesion type. ANOVA will be performed to determine if the treatment significantly impacted disease severity.
2. Field trials will be done with the specialty variety Purple Viking in central Oregon on the property of an organic producer, Rainshadow Organics. Potatoes will be grown on 10 rows 1200-feet long using current practices. During planting the first week of May, we will flag four blocks of ~20 plants for each treatment (two treatments: mock and 50 mM thiamin) in a randomized complete block design. Shortly after emergence, we will start applying thiamin or a mock solution containing Safer Soap as surfactant on a weekly basis. At harvest in early September, common scab severity and incidence will be evaluated as described above.
3. To ascertain the global transcriptomic response to thiamin in the context of immune priming against common scab disease, we will select three biological replicates of tuber skin samples from each treatment condition (mock vs. 50 mM foliar thiamin, + Streptomyces infection = four total treatment groups) from the greenhouse trials at harvest time for RNA-seq. RNA-seq analysis will enable the selection of marker genes for the immune priming response to thiamin in tuber tissue, for which expression will be verified via qRT-PCR.
