Location: Temperate Tree Fruit and Vegetable Research
Project Number: 2092-22430-003-053-I
Project Type: Interagency Reimbursable Agreement
Start Date: Mar 1, 2023
End Date: Feb 28, 2025
Objective:
1. Determine the prevalence of Wolbachia infection in recently collected U.S. samples and historically collected European samples.
2. Determine if Wolbachia infections alter the parasitism rates of pear psylla under laboratory conditions.
3. Determine the effects of a warming climate on Wolbachia infection in T. insidiosus under laboratory conditions using insect cell lines and live insects.
Approach:
This work will be conducted at the Wapato, Washington, ARS Temperate Tree Fruit and Vegetable Research Unit.
1. Determine the prevalence of Wolbachia infection in US samples and previously collected European samples.
Hundreds of specimens of T. insidiosus have been collected in 2020-2022 from Washington, Oregon, California, Utah, New York, and West Virginia. We will perform DNA extractions and use universal primers used to test for the presence of Wolbachia. We also have voucher samples of Trechnites collected from Europe prior to the known introduction of T. insidiosus in the U.S. Those specimens will also be assayed for the presence of Wolbachia using the same methods. The amplified DNA will then be processed for sequencing using established methodology to verify the identity of the Wolbachia strain as well as determine the genetic relatedness of the Wolbachia bacteria. This information may reveal if the earlier introductions of T. insidiosus by ARS scientists were successful, or if T. insidiosus had already been present in the U.S.
2. Determine if Wolbachia infections alter the parasitism rates of pear psylla.
Parasitism rates will be tested using laboratory assays exposing pear psylla nymphs to T. insidiosus adults. In late summer of 2023 pear psylla mummies will be collected from orchards where known variation in Wolbachia infection exist. Using an existing colony of pear psylla maintained in Wapato, Washington, T. insidiosus adults will be given access to pear psylla nymphs for a set time period. The T. insidiosus will be assayed for the presence of Wolbachia and the offspring of uninfected×infected individuals will then be assayed to compare the efficacy of Wolbachia infected individuals versus those not infected.
3. Determine the effects of a warming climate on Wolbachia infection in T. insidiosus.
Cell lines will be developed to test the effects of increasing temperatures on Wolbachia-infected T. insidiosus cells. Due to previous research indicating reduced Wolbachia infection rates in warmer climates, we believe it is plausible warmer average temperatures will impact Wolbachia prevalence in T. insidiosus. To determine if this is the case, we will take two simultaneous approaches. The first will be rearing colonies of T. insidiosus under a gradient of controlled temperatures ranging from the summer average in Washington up to +4° C higher. The second approach will follow the first, but cell lines will be cultivated using standard insect cell line practices. Cell lines will be exposed to the same temperature gradient as outlined above.
