An ARS-led team had a key role in the newly completed, history-making venture that deciphed the structure of all genes in a little mustard family plant, Arabidopsis thaliana. The Albany, CA, team helped determine the structure, or sequence, of the genes on the largest of the five Arabidopsis chromosomes. The worldwide Arabidopsis project yielded the first complete, publicly available catalog of the structure of all genes that come into play in the life of a flowering plant, from seed to flower to fruit. Now, the Albany team and other researchers are working to discover the function of each of the Arabidopsis genes. If the scientists determine, for example, what genes control resistance to insects or diseases, they might then be able to shuttle these genes into plants that lack natural protection. Or the researchers may retool the genes to boost their effectiveness. Arabidopsis, also known as mouse ear cress or thale cress, has less genetic material than familiar crop plants such as corn or wheat. But discovering the structure and—next—the function of Arabidopsis genes helps reveal clues to the form and function of genes in all flowering plants.

ARS/University of California at Berkeley Plant Gene Expression Center, Albany, CA
Athanasios Theologis, (510) 559-5911, theo@nature.berkeley.edu

Studies of transgenic potatoes show that one cultivar with the Bacillus thuringiensis (Bt) gene has lost its resistance to the golden nematode, Globodera rostochiensis. This pest can wipe out entire potato crops by feasting on the plants' roots. So far, these tiny worms have attacked the U.S. potato crop only in New York. Using bioassay tests, ARS scientists found that the nematode infected and reproduced freely on Atlantic NewLeaf clone 6. This potato variety was produced by introducing the Bt gene for golden nematode resistance into the cultivar Atlantic. But two other clones of Atlantic NewLeaf from different Bt transformations with Atlantic maintained their resistance. DNA analysis of these Atlantic NewLeaf clones showed they contained the marker that indicates the presence of the gene for golden nematode resistance. This suggests that at some place in the transformation process that produced Atlantic NewLeaf clone 6, the expression of this gene was affected and the effect persisted through prerelease testing. The scientists presented their findings at the July meeting of the Potato Association of America in Colorado Springs, CO.

Plant, Soil, and Nutrition Laboratory, Ithaca, NY
Bill B. Brodie, (607) 255-2158, ars-ithaca@cornell.edu

Cadet and Jacinto, two new rice varieties with a gene for improved cooked rice texture, entered commercial production this year, thanks to new technology that speeded their development. The new varieties, which produce rice low in amylose content, are adapted to southern U.S. and European growing regions. Though new variety development normally takes 7 to 10 years, ARS scientists and their colleagues at the Texas Agricultural Experiment Station, College Station, did the job in just 5. The researchers used a biotechnological process called marker-assisted selection to locate desirable genes in noncommercial varieties and deployed them into the new varieties through conventional breeding.

Rice Research, Beaumont, TX
Anna M. McClung, (409) 752-5221, a-mcclung@tamu.edu

Light reflected from colored mulches increases the size, aroma, and flavor of sweet basil leaves. Sweet basil (Ocimum basilicum L.) is a high-value specialty crop that is used fresh as an herb or as a dried spice to add a distinct aroma and flavor to food. ARS scientists, who pioneered the use of colored plastic mulches, found that two components of reflected light enhance plant growth: a low percentage of blue light and a high ratio of far-red to red light. Red plastic mulch reflects onto plants higher amounts of certain growth-enhancing wavelengths of sunlight. Basil is grown commercially and by many home gardeners outdoors in full sunlight over plastic mulches that conserve water, control weeds, and keep soil from splashing onto leaves. By using colors other than the standard black for these soil covers, the scientists were able to keep the benefits attributed to black plastic mulch, yet alter the amounts of blue, red, and far-red light reflected to developing leaves. The color of reflected light acted through the plants' natural growth-regulating system to increase leaf size, aroma, and concentration of soluble phenolics, some of which are important antioxidants. The study was reported in the March issue of the Journal of Agricultural and Food Chemistry.

Coastal Plains Soil, Water, and Plant Research Laboratory, Florence, SC
Michael J. Kasperbauer, (803) 669-5203, kasper@florence.ars.usda.gov

A study now in progress should help farmers determine which variables limit yields and whether precision agriculture techniques could improve profitability. Typical scientific research takes place on small field plots, with researchers modifying one or two variables and extrapolating results to the real world. Now, in a 5-year study of a complete agricultural system, ARS scientists are measuring all possible environmental conditions and farming practices that could affect yield on two commercial farms in Colorado. Their goal: to find the most significant yield determinants. They're scrutinizing inputs like water, fertilizer, and pesticides to see if intensive management practices—like variable-rate application—benefit the environment and are financially feasible for the farmer. So far, about halfway through the study, researchers have found that farmers were overwatering with their center-pivot irrigation systems. Now the farmers apply less water. Colorado State University, several state and federal agencies, and six private companies are participating in the research. The multidisciplinary team plans to develop a decision-support tool based on project results to help farmers decide whether precision farming would be beneficial. It's also analyzing techniques that measure large field areas economically—such as remote sensing—in order to reduce the cost of precision farming.

Water Management Research Unit, Fort Collins, CO
Dale F. Heermann, (970) 491-8511, heermann@wmu.aerc.colostate.edu

Growers may have problems growing canola on land previously used to raise cotton. Louisiana producers recently became aware of this because they wanted to use canola (Brassica napus L.) as a rotation crop on well-drained soils where cotton (Gossypium hirsutum L.) is normally planted. But a common contact herbicide used in cotton production contains arsenic, and crop plants have varying degrees of tolerance to arsenic compounds. To determine if soil arsenic would influence canola growth, ARS and Louisiana State University scientists conducted a controlled-climate chamber experiment using three soils with histories of cotton production (Commerce, Rilla, and Sterlington silt loams) using three arsenic application rates (0, 5, and 10 milligrams per kilogram of soil). When arsenic was added to the soil, seedlings grown in the Commerce and Sterlington soils absorbed more of the element than those grown in the Rilla soil, which showed little change. Arsenic addition had no measurable effect on short-term plant growth. However, arsenic-toxicity symptoms eventually developed on leaves of plants in all treatments where the metal had been applied. The scientists concluded that the growth of canola plants can be adversely affected by recent application of any arsenic compound.

National Soil Tilth Laboratory, Ames, IA
John L. Kovar, (515) 294-3419, kovar@nstl.gov