The center of origin of peanut is located in South America, specifically in southeastern Bolivia and northwestern Argentina. In the early 1990s, peanut production moved to more southern areas of Argentina’s Córdoba Province, and as a result, a new disease emerged. Peanut smut, a fungal disease caused by Thecaphora frezzii, can now be found in 100% of Argentina’s peanut areas.
As word about the severity of peanut smut began reaching scientists in the United States, the industry, collectively, knew that the best hope was to keep it out of U.S. peanuts as long as possible and, in the meantime, to find a solution to the fungal disease.
Seeing the disease firsthand in Argentina, University of Georgia research plant pathologist Tim Brenneman considered the risk of the disease so great that he left the boots he had been wearing in the fields behind in the airport so as not to track any possible contaminated soil into the country.
At the NPRL, Renee Arias De Ares, research plant pathologist who is working on peanut smut, echoes Dr. Brenneman’s assessment of the severity of the disease.
“Prior to 2017, the United States was still importing peanuts from Argentina of both raw and blanched peanuts. Then, in 2017, the United States stopped importing raw peanuts and only imported blanched peanuts. “However, in talking with people who have worked with this pathogen, we now know the pathogen can survive blanching,” Arias De Ares says. “The spores of this pathogen can even survive pure bleach.”
Knowing this seemingly unkillable soil-borne pathogen will result in 35% losses in the field, an arrangement with the people of Argentina and their institutions was established to do research on the disease in an effort to get ahead of the problem before it emerged in the United States.
“Through our agreement, they sent us phenotypic data from peanut plants and DNA from plants and DNA from the pathogen. We only received DNA, not the actual pathogen,” she explains. “With this, we were able to sequence the genome of the pathogen and determine some important genes, such as those controlling fungicide resistance.
“In 2023, we published the whole genome of the pathogen,” Arias De Ares. “Now, more importantly, we built a collaboration with Dr. Alicia Massa, NPRL research geneticist, to genotype resistant material from Argentina.
“Dr. Massa has identified resistance to peanut smut in the germplasm collection in Griffin, Georgia. Not only that, she has developed molecular markers that will help peanut breeders introduce resistance into peanut varieties.”
Overall, Arias De Ares says they have worked to identify germplasm with smut resistance and to understand the genetics of the pathogen. Knowing the genome of the pathogen will help with analyzing potential variants and contribute to the development of enhanced germplasm with broader and long-lasting resistance.