EXCLUSION OF AFLATOXIN PRODUCING FUNGI FROM COTTONSEED. Using recently patented technologies, scientists were able to demonstrate biocompetitive exclusion of aflatoxin producing molds by naturally occurring non-toxic mold "cousins" in field-grown cottonseed. Application of these non-toxic mold cousins to cotton fields reduced aflatoxin contamination of cottonseed by 90%. Applications have been made to commercial fields and have been shown to have long-term influences on the aflatoxin producing potential of fungi in a treated area. The technology will be useful for reducing the vulnerability of crops to aflatoxin contamination. The presence of aflatoxins in cottonseed, corn, peanuts and other crops can prevent crop use for food and feed. U. S. Patent 5,294,442. [CONTACT: Dr. Peter J. Cotty, 504-286-4391, email: pjcotty@srrc.ars.usda.gov]

A U.S. PATENT (#6,703,540) on "TRANSFORMATION OF PLANTS WITH A CHLOROPEROXIDASE GENE TO ENHANCE DISEASE RESISTANCE" has been issued to scientists of the Food and Feed Safety (FFS) Research Unit. Co-inventors of the patent are Thomas Jacks, Jeffrey Cary, Kanniah Rajasekaran, Thomas E. Cleveland (FFS) and Karl-Heinz Van Pée of Dresden University, Germany. The invention provides a method of making plants resistant to plant pathogens by transformation of host cells with a bacterial gene encoding a nonheme haloperoxidase. Transgenic tobacco and cotton plants expressing a nonheme chloroperoxidase showed increase resistance to phytopathogens in vitro and in planta. The FFS scientists also demonstrated the ability in situ of the gene product to inhibit growth of fungal pathogens, including Aspergillus flavus in cottonseeds. Aflatoxin contamination of cottonseeds and other food and feed crops such as corn, peanuts and tree nuts poses a very high public health risk because of the extremely carcinogenic nature of the toxins. In addition, transgenic plants expressing the chloroperoxidase gene have shown efficacy against a number of other common plant pathogenic bacteria and fungi and should be of value in increasing crop yields and quality as well as reducing the need to apply chemical fungicides

New Cottons “Pack a Punch” Against Fungi

By Jan Suszkiw
Agricultural Research Service scientists are testing new cotton lines whose seed may pack a knockout punch against microbial attackers.The plants' “punch” is a small protein called a peptide. Shown for the first time in test tube trials, leaf and seed extracts from cotton plants expressing the synthetic peptide D4E1 inhibited up to 100 percent of germinating Aspergillus flavus and other fungi within 30 minutes of exposure. The next step is to inoculate the cotton bolls with the fungus to see if D4E1 stops it from germinating on the seed, according to Thomas Cleveland, who leads ARS’ Food and Feed Safety Research Unit in New Orleans.

A. flavus, one of 25 fungi and bacteria that succumb to D4E1, is of particular interest because it can contaminate cottonseed with aflatoxin. Because it’s harmful to humans and other animals, aflatoxin threatens the marketability of cottonseed, which is processed into edible oil, a high-protein meal, and other products valued at $500-700 million annually.

Eventually, according to Cleveland, the peptides could offer a surrogate defense for cotton plants lacking sufficient resistance to microbial infection. This also could offset the need for chemical fungicides.

To engineer the cotton, ARS biologists Kanniah Rajasekaran and Jeffrey Cary first synthesized a gene for making D4E1 using a blueprint of amino acids — the building blocks of all protein — from Demegen, Inc. Dow AgroSciences LLC subsequently licensed the technology and is collaborating with ARS under a 1998 cooperative research and development agreement to develop disease resistant cottons.

The researchers used the microbe Agrobacterium tumefaciens to insert D4E1 into cotton seedling cells and developed a clump of genetically transformed callus material. From this, they regenerated 100 to 150 plants, but chose only 10 for further propagation and progeny testing.

The ARS-Dow AgroSciences LLC team is using specialized antibodies and mass spectrometry techniques to determine how much D4E1 is made by cottonseed, and pinpoint its location inside cotton cells. ARS is the U.S. Department of Agriculture's chief scientific agency.