ARS News Service Tip Sheet 5-10-97
Agricultural Research Service, USDA
Contact: Jim DeQuattro; 301-344-2756; [email protected]
New Test Speeds Search for Aflatoxin Biocontrol
Scientists can now quickly identify whether a natural yeast strain has the potential to control aflatoxin on tree nuts, thanks to a new lab test in which red means no and white means yes.
Aflatoxin, produced by certain fungi, can be a threat to food and feed safety. The scientists, with USDA's Agricultural Research Service in California, are seeking to identify natural, harmless yeasts with the best potential for suppressing the fungi.
So far, they have screened dozens of yeasts with the new test. ARS plant physiologist Sui-Sheng Hua (schwi-shing hwa) and colleagues developed the new test at ARS' Western Regional Research Center, Albany, Calif. With this test, scientists need only see what happens after they put into a laboratory dish both a candidate yeast and a special Aspergillus strain. This strain, developed by other researchers in the 1980's, has a genetic mutation. It forms a red-orange pigment, norsolorinic acid, or NOR, as a nontoxic precursor to making aflatoxin.
Scientific contact: Sui-Sheng Hua, Plant Protection Research Unit, ARS Western Regional Research Center, Albany, Calif., phone (510) 559-5905, fax 559-5777, e-mail [email protected].
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Scientists Identify Chemical That Triggers Plant "SOS" Call
An insect chemical that prompts corn seedlings to send out a distress signal has been chemically isolated, identified and artificially reproduced by U.S. Department of Agriculture and cooperating scientists.
The chemical, called volicitin, is secreted in the saliva of beet armyworm caterpillars and other similar pests that feed on crops. The researchers say volicitin causes plants to produce chemical aromas, which in turn lure beneficial insects to attack the crop pests. The finding, published in the
May 9 issue of the journal Science, is the latest in an ongoing research effort to find environmentally friendly ways to control crop pests.
The identification of volicitin is a key finding in understanding the natural defense systems that plants use to defend themselves against insect attack. In the January issue of the journal Nature, the scientists reported for the first time that cotton plants actually synthesize distress-signal
chemicals when attacked by pests--and that the chemicals aren't simply stored inside the plant. They also found that the distress signals emanate from the entire plant--not just from the spot where the pest has fed.
Scientific contact: James H. Tumlinson, Center for Medical, Agricultural and Veterinary Entomology Research, USDA/ARS, Gainesville, Florida, phone (352) 374-5730, fax (352) 374-5707, email
[email protected]
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Cloudy is Good--When It Pertains to Citrus Juices
Believe it or not, we like our orange juice cloudy. A pitcher of orangejuice sitting in the refrigerator that has separated into a layer ofsolids at the bottom and clear liquid at the top is considered spoiled. Consumers tend to think that clear, unclouded juice has been watered down or lacks freshness. The marketing of fresh citrus juices is severely restricted because an enzyme present in citrus peel and fruit clarifies the juice, eliminating the cloud.
U.S. Department of Agriculture scientists in Winter Haven, Fla. discovered that a form of the enzyme pectinmethylesterase in citrus peel causes the most rapid juice cloud breakdown. Forms of the enzyme present in the fruit itself work more slowly to decloud juice. The enzyme also causes frozen concentrated citrus juice to gel and causes bits of solid matter to form in beverages containing citrus juices.
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Scientific contact: Randall C. Cameron, USDA-ARS Citrus and Subtropical Products Laboratory, Winter Haven, Fla; phone 941-293-4133, Ext.124; fax 941-299-8678; e-mail [email protected]
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Extra Vitamin E May Thwart Infections in the Elderly
An extra 200 milligrams of vitamin E every day can go a long way toward reducing infections and potential cancers in older people, according to findings of a U.S. Department of Agriculture study to be published tomorrow (May 7) in the Journal of the American Medical Association.
Men and women over age 65 who took daily vitamin E supplements had clinically relevant improvements in their immune system's response to foreign antigens, substances that cause the body to produce antibodies. Those getting the 200-milligram dose--equivalent to 200 International Units (I.U.)--had the strongest responses, said study leader Simin Nikbin Meydani.
Eighty men and women participated in the six-month study at the USDA Human Nutrition Research Center on Aging at Tufts in Boston. Meydani, a nutritionist and immunologist, and colleagues divided the volunteers into four groups to test three different levels of vitamin E--60, 200 or 800 milligrams--versus a placebo.
"It surprised us that 200 milligrams of vitamin E was the optimal level, not 800 milligrams," said Meydani, who had earlier tested the higher dose on elders with positive results. "Even those taking 60 milligrams daily had improvements in some tests."
"It appears that 200 milligrams was a threshold level for these volunteers," Meydani noted. "They got no added benefit from taking more."
Scientific contact: Simin Nikbin Meydani, DVM, PhD, chief, Nutritional Immunology Laboratory, USDA Human Nutrition Research Center on Aging at Tufts, Boston, Mass. 02111, phone (617) 556-3129, fax 556-3224, e-mail [email protected].
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Keeping cotton swabs mildew-free is critical to physicians and consumers. A new sterilization treatment, using the anti-bacterial agent methocel, can ensure green and black mildew never gain a toehold.
The key is applying methocel properly. A scientist with USDA's Agricultural Research Service developed effective methods for treating the swabs with this environmentally-safe mildew killer, based on research begun at a private company and completed at ARS.
Heat-based bleaching treatments that give cotton swabs their clean white look usually kill microorganisms. But heat, humidity in darkness and the cotton's inner moisture can undo the bleach's protective barrier over time. Tests with methocel show a longer-lasting protection.
Scientific contact: D. V. Parikh, ARS Southern Regional Research Center, New Orleans, La. , phone (504) 286-4331, fax (504) 286-4234, e-mail [email protected].
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