
Newly
Approved Fungus May Help "Clean Up" Cotton By Erin
Kendrick-Peabody July 28, 2003A fungus discovered by an
Agricultural Research Service scientist
crowds out its relatives, steals their food and space--and could prove to be an
important ally to farmers across Arizona and Texas. Known simply as AF36, the
naturally occurring fungus crowds out harmful fungi that can contaminate crops,
a burden costing the U.S. cotton industry up to $10 million annually. ARS scientist Peter J. Cotty discovered this "atoxigenic" strain
of fungus and used it to invent a biocontrol strategy for fighting fungal
toxins that may spoil some crops. Now, after 11 years of studies and field
tests on more than 80,000 acres, AF36 has received approval from the U.S.
Environmental Protection Agency for use on
cotton throughout Arizona and Texas. Aflatoxin is a toxic compound produced by some strains of the fungus
Aspergillus flavus that may occur on cottonseed, corn and peanuts.
Cottonseed is the main feed of dairy cows, so a safe milk supply relies on
"clean" cottonseed. Because toxins may be transferred to milk, the
U.S. Food and Drug Administration maintains a
stringent 20-parts-per-billion limit on aflatoxin in cottonseed. Anything more
renders the cottonseed unmarketable. Cotty, a plant pathologist at ARS'
Southern
Regional Research Center in New Orleans, La., developed a strategy to aid
farmers: alter fungi in fields so that they don't produce aflatoxins. It was a
simple-sounding solution, but one requiring an expert knowledge of fungi and 17
years of lab and field studies. Fungi compete with one another for limited space and nutrients to survive.
Playing on this biological fact, Cotty seeded affected fields with the AF36
strain he discovered in Arizona, essentially pitting this benign strain of
A. flavus against toxin-producing ones. The good news: In the field
tests, AF36 reduced toxic strains by up to 90 percent. The real advantage of AF36, however, lies in its delivery. Wheat seed,
colonized with the beneficial strain, is distributed on top of the soil after
the last cultivation. With a ready food supply of wheat, AF36 gets a step ahead
of other fungi in its colonization. ARS collaborated with the Arizona Cotton
Research and Protection Council to develop a commerical process for
producing and delivering atoxigenic formulations. A facility in Phoenix, Ariz.,
has the ability to generate up to 1.5 million pounds of atoxigenic product
annually, a feat that would require several years in a laboratory. A U.S. Department of Agriculture multicrop aflatoxin working group
collaborated with state agencies and local and national industry partners to
provide key support to this research effort. ARS is the USDA's chief in-house
scientific research agency. U.S. Department of Agriculture |