Survival of a fast-growing strain of lupin rhizobia in sonoran desert soils

Bacteria isolated from the roots of lupins are normally slow-growing, but an effective, fast-growing strain (generation rime, 3.6 h) of Rhizobium was isolated from a species of Lupinus native to the Sonoran Desert near San Felipe, Baja, Mexico. This strain (Lupin 43) possesses multiple ffageila and produces acid in a denned medium. Field and incubator studies were conducted to determine if the Actaptation of the characteristics of fast-growing strains enabled Lupin 43 to survive under the desert conditions of the southwestern U.S. In the field, where no moisture was added after initial inoculation, Lupin 43 survived in significantly higher numbers than Lupin 96AI 1, a commercial, slow-growing strain. In laboratory studies, at a constant moisture tension of - kPa, differences in survival between the two strains were mostly dependent on soil texture, pH and temperature.