Location: Foreign Disease-Weed Science Research
Project Number: 8044-22000-051-041-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2025
End Date: Aug 31, 2026
Objective:
The United States is one of the world’s leading producers and exporters of peanuts, making crop health a critical concern for domestic agriculture and international trade. Thecaphora frezzii causes a serious disease of peanuts. It first appeared in a commercial peanut production in Argentina in 1995, and the fungus has since spread to all peanut-producing regions of that country. In some cases, disease incidence has exceeded 50%. Peanut smut has been recently detected outside of Argentina, indicating potential movement through trade. Because of this, there is concern about the potential for pathogen establishment in the United States. While significant progress has been towards identification of resistant germplasm for use as a disease control strategy, growers have begun to notice that even resistant varieties are now getting infected, indicating that the pathogen may be changing to overcome this resistance. To address this, we will collect and sequence T. frezzii isolates from naturally infested fields in Argentina from both susceptible and resistant host varieties and determine if and how the pathogen is changing to overcome host resistance. This information is key to assess how durable the host resistance is and will inform how the disease is managed should it establish in the U.S.
Approach:
The Cooperator will plan and take two collecting trips to naturally infested fields during peanut harvest time. The Cooperator will visit locations in Cordoba, the primary peanut-producing region in Argentina for the first trip, as well as Salta, a peanut-producing region in a much more isolated region of the country, for the second trip. Approximately five peanut-growing fields will be visited in each location. In both of these locations, peanut varieties that are susceptible and resistant are being grown in the same field. The Cooperator will take a subset of the harvested peanuts (both resistant and susceptible varieties from the same field) back to the lab. The peanuts will be hand shelled, and whether or not they are infected with T. frezzii will be noted. If they are infected, spores from a single peanut will be placed in a 1.5 ml tube, parafilmed and prepared for shipment to the USDA-ARS Foreign Disease-Weed Science Research Unit (FDWSRU) in Frederick, MD. Spores from up to ten individual peanuts per variety per field will be saved and sent. The goal is to collect ~300 T. frezzii isolates. The Cooperator is to obtain all necessary provincial and country permits for collecting and export. Once in the possession of ARS, the spores from individual peanuts will be subjected to high-throughput sequencing where it is possible to examine for changes in pathogen DNA that may be facilitating this observed breakdown in host resistance.