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Rotting potatoes harbor harmful toxins.

Rotting potatoes harbor harmful toxins

Shriveled brown spots on potatoes may indicate deadly trichothecene toxins. a new study suggests that potentially harmful levels of the poisons may occur in potatoes infected with a major fungal perpetrator of potato dry-rot, says coauthor Anne E. Desjardins, a biochemist at USDA's Agricultural Research Service in Peoria, III.

If a careful survey of store-bought potatoes confirms these preliminary findings, the safety of infected potatoes "may be something to think about," Desjardins says. However, she emphasizes that it is unclear how much harm the toxin levels found in the study would cause in humans.

"There's routine screening for toxins in corn and wheat ... but potato farmers have never really thought about it," Desjardins says. She and co-worker Ronald D. Plattner were the first to show that strains of Fusarium sambucinum fungi from around the world can produce trichothecenes in potatoes. One previous study demonstrated that store-bought potatoes in France contain potentially dangerous levels of these toxins, but there have been no studies of toxin levels in naturally infected potatoes elsewhere, Desjardins says.

Trichothecene toxins take their toll on fast-growing cells, such as blood, by blocking protein synthesis. Even at low levels, they can cause symptoms in humans ranging from vomiting and hair loss to immunosuppression, central nervous system dysfunction, coma and death, Desjardins says.

Desjardins and Plattner infected potatoes with 15 fungal strains isolated from diseased potato tubers in North America, Australia, Europe and Asia. They found that 14 of the strains produced trichothecene toxins in inoculated tubers, indicating that the toxin production is very common among these fungi, Desjardins told SCIENCE NEWS.

"And the levels are quite high," she says. They found up to 5 micrograms of toxin per gram of fresh-weight potato tissue, a concentration higher than that allowed in Canadian grain for export and higher than that known to cause adverse effects in animals, she says. Because Desjardins and Plattner incubated their experimentally infected potatoes for only six days, in contrast to the months potatoes typically sit in bags, "we're [probably] only looking at the tip of the iceberg," she says. However, the levels in experimentally inoculated potatoes may be different from those in naturally infected potatoes, warns USDA organic chemist Odette L. Shotwell, also in Peoria.

Even apparently disease-free parts of infected potatoes contained the fungal toxin, at levels about 10 percent of those in the diseased portions. So removing rotted parts won't remove all of the toxin, says Desjardins. And since trichothecenes are heat stable, "it seems unlikely that [they] would be destroyed by the usual procedures to prepare potatoes for human consumption," the researchers write in the March/April JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY.
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Title Annotation:Food Science
Publication:Science News
Date:Apr 15, 1989
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