A lowly soil bacterium first cultured two decades ago by Agricultural Research Service (ARS) scientists is now enjoying "celebrity" status as a yield-boosting, commercial soybean inoculant.

Since licensing rights on the bacterium in 1994 from ARS, Urbana Laboratories, of St. Joseph, Mo., has sold enough of the inoculant to treat 14 million acres of soybeans. Formerly known as Bradyrhizobium japonicum strain TA11Nod+, and now known commercially as the "USDA strain," the bacterium converts gaseous nitrogen into forms soybeans can use for optimal growth and higher yield. This process also saves on synthetic fertilizer costs and nourishes soils at rates less likely to affect groundwater.

ARS microbiologists David Kuykendall and Jim Hunter originally developed, tested, and in 1991 patented the Nod+ strain as an improvement over existing Bradyrhizobium strains that soybean farmers had been using.

Kuykendall, with the then-named Soybean and Alfalfa Research Laboratory in Beltsville, Md., is now at the Molecular Plant Pathology Laboratory there. Hunter, his associate, is with the agency's Plant, Soil and Nutrient Research Unit in Fort Collins, Colo.

In early tests, their Nod+ strain fixed 50 percent more nitrogen when inoculated onto soybean roots than did B. japonicum 1-110, a top-performing inoculant. Subsequent field trials conducted by Extension scientists at 377 sites across 18 states indicated that use of the nod+ strain boosted soybean yields by 2 to 3 bushels per acre.

Since the Nod+ strain's commercial introduction by Urbana, Hunter estimates the new inoculant has increased soybean yields by nearly 30 million bushels. At $5 per bushel, this translates to an additional $150 million in gross income for farmers.

A longer story about this work appears in the May issue of Agricultural Research magazine on the World Wide Web at:

http://www.ars.usda.gov/is/AR/archive/may02/bact0502.htm