Bacterial blotch, a disease that has damaged white button mushrooms for more than a century, is caused by a complex of more than 17 pathogenic bacterial species rather than the single pathogen long blamed for it, according to a study by the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) published in Microbiological Research.
Blotch leaves brown or yellow marks on the caps, lowers their value, cuts yields and shortens shelf life. Symptoms sometimes appear only after the mushrooms have been shipped to shops or bought, which makes it hard for growers to guarantee quality.
The team collected diseased mushrooms from several production facilities across the southern United States and combined DNA sequencing, chemical profiling and standard laboratory tests. "We found more than 17 different species of pathogenic bacteria associated with the disease," said lead author Sameerika Mudiyanselage, a doctoral student at UF/IFAS. Two well-known pathogens dominated, she said, but the team also found a surprisingly high level of another group of bacteria not linked to the disease before.
Because several species can cause the same disease in the warm, humid rooms where mushrooms are grown, treatments aimed at one pathogen may not be enough, and growers may need wider diagnostic tests. "For years, the industry has struggled with treatments that provide inconsistent results against bacterial blotch," said co-author Samuel Martins, an assistant professor of plant pathology. A separate $7 million US Department of Agriculture grant involving Penn State, the University of Delaware and UF/IFAS is developing better diagnostics.
The researchers are now testing plant essential oils, beneficial microbes and other biological products as alternatives to chemical treatments. More work is needed to see how well they perform on working farms.
Photo: Andrew Bossi / Wikimedia Commons (CC BY-SA 2.5)
Source: ScienceDaily (Agriculture & Food)
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