Extension Ag Update
September/October 2004
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Agricultural Pesticides Found in the Environment, Not Just on Crops

D. T. Waite, A. J. Cessna, R. Grover, L. A. Kerr, and A. D. Snihura
Source: Journal of Environmental Quality, Volume 33

Scientists from Environment Canada and Agriculture and Agri-Food Canada measured the concentrations of seven popular agricultural herbicides in the air, atmospheric deposits (rain plus dust-fall), and pond water at two Saskatchewan farm ponds in 1989 and 1990, as seen in the Journal of Environmental Quality (September 2004 and January 2002). Of the seven herbicides measured, all were found in the air. Six of the seven were found in atmospheric deposits. And six of the seven were found in the pond water. Don Waite, Environment Canada scientist and team leader stated, "These herbicides represent only a small number of the agricultural pesticides applied annually in North America. Research should be continued on their movement and on the cumulative impacts on sensitive ecosystems."

Exploring Sorghum's Knack for Keeping Weeds Away

Luis Pons, (301) 504-1628, lpons@ars.usda.gov, ARS News Service, USDA

Like people, most plants need their space. How much sunlight they get and how large they grow are among the factors directly linked to how much room plants have around them. And when it comes to protecting its space, few plants are as assertive as sorghum. That's why Agricultural Research Service scientists who are seeking ways to keep weeds away from food crops have taken a special interest in this drought-tolerant grain. Sorghum has been gaining favor in the United States because of its natural cancer-fighting compounds and digestibility by people with gluten intolerance.

Sorghum is one of many plants with allelopathic traits, according to Stephen Duke, a plant physiologist in the ARS Natural Products Utilization Research Unit at Oxford, Miss. The roots of allelopathic plants release plant toxins into the soil that hold encroaching plants at bay. Duke and his colleagues--molecular biologists Scott Baerson, Daniel Cook and Ziquiang Pan; plant physiologist Franck Dayan; and chemist Agnes Rimando--agree that sorghum's allelopathic properties are stronger than those of most other plants.

Sorghum's main weapon is sorgoleone (sor-GO-lee-own), a compound that's more active in fighting weeds than most other allelopathic compounds in other plants. Sorghum produces sorgoleone at the root and the root hairs. Researchers from the ARS unit are developing the basic information needed to genetically increase the production of sorgoleone in sorghum, according to Baerson. They're aided by a cDNA library they developed with help from University of Georgia professor Lee Pratt.

While this overall research may one day lead to introducing allelopathic traits into other crops, care must be taken to ensure that allelochemicals have no negative effects on nontarget organisms, including people, according to Duke. He says that it's unlikely that allelopathy can totally replace herbicides in weed control. However, any naturally protective traits that could even marginally reduce herbicide use would be financially and environmentally significant. To read more about this research check out www.ars.usda.gov/is/AR/archive/may05/sorghum0505.htm

New "Waxy" Wheat Being Tested for Public Release

Jan Suszkiw, (301) 504-1630, jsuszkiw@ars.usda.gov, ARS News Service, USDA

Agricultural Research Service (ARS) scientists are field-testing a soft white spring wheat whose starch could open the door to novel food uses. That's the hope of Craig Morris, a cereal chemist who developed the new wheat, called Penawawa-X, at the ARS Western Wheat Quality Laboratory at Pullman, Wash. In that and other Pacific Northwest states, soft white wheat is typically grown for making cookies, cakes, noodles, flatbreads and other Asian or Middle Eastern baked goods. The wheat's starch consists of two kinds of glucose polymer: a branched form called amylopectin, and a straight-chain form called amylose. According to Morris, who directs the ARS lab, Penawawa-X would be one of the first commercial, soft white spring wheats with 100-percent amylopectin starch, a trait known as "full-waxy." As such, it forms a paste at lower temperatures and swells with more water than regular or partially waxy wheat starches (those containing less than 25 percent amylose).

Waxy starch gels also do not lose water upon exposure to freezing and thawing. Food-bodying agents, shelf-life extenders and shortening replacement are some potential uses envisioned for full-waxy starches, including those from rice, corn and barley. Morris developed Penawawa-X using conventional plant breeding techniques that enabled him to combine three deficient forms of the gene for granule-bound starch synthase (GBSS), the enzyme responsible for making amylose. Since the deficient forms can't make GBSS, no amylose is made either. Besides novel food uses, the full-waxy starch may have industrial applications, perhaps in adhesives.

To identify possible uses, Morris' lab sent dozens of samples of Penawawa-X wheat to bakers, millers, food companies and others. Under an ARS cooperative research and development agreement, one company is exploring commercial use of the wheat's starch, flour, bran and other components. Multistate field trials are now under way to generate yield and other data necessary to register Penawawa-X and to publicly release it.