A 100-Year-Old Mushroom Disease Turns Out to Have More Than 17 Bacterial Culprits

A University of Florida study has uncovered an important clue about bacterial blotch, a disease that has affected white button mushrooms for more than 100 years. The disease lowers yields, shortens shelf life and reduces market value by causing brown or yellow discoloration, and in some cases symptoms do not appear until the mushrooms are already in stores or homes.

Researchers from the UF Institute of Food and Agricultural Sciences (UF/IFAS) found that bacterial blotch is not caused by a single pathogen, as previously believed, but by a complex mix of harmful bacterial species that thrive in the warm, humid indoor conditions used for mushroom production. The team used DNA sequencing, chemical profiling and traditional laboratory testing on infected mushrooms collected from several production sites across the southern United States.

"We found more than 17 different species of pathogenic bacteria associated with the disease," said Sameerika Mudiyanselage, the study's lead author and a doctoral student at the UF/IFAS Tropical Research and Education Center. Two well-known bacterial pathogens dominated the known disease profile, but the team also detected a surprisingly high level of another bacterial group that had not previously been linked to the disease, which may help explain why treatments have produced inconsistent results.

"For years, the industry has struggled with treatments that provide inconsistent results against bacterial blotch," said Samuel Martins, co-author and assistant professor in the UF/IFAS Department of Plant Pathology. As part of a separate $7 million U.S. Department of Agriculture grant involving Penn State, the University of Delaware and UF/IFAS, the researchers are developing advanced diagnostics and testing plant-based essential oils, beneficial microbes and other biological products as more sustainable alternatives to chemical treatments. The findings were published in the journal Microbiological Research.