Soil fertilization limits the genetic diversity of Rhizobium in bean nodules

Abstract

The effect of soil fertilization on the genetic diversity of Rhizobium isolates from bean nodules was estimated by multilocus enzyme electrophoresis. In two-year trials, we found that levels of fertilization commonly used in agricultural fields in Mexico (N, P, K, 40-40-20) diminished the genetic diversity in the nodule population in some, but not all Phaseolus vulgaris cultivars. The decrease in genetic diversity may be attributed in part to the N fertilization because an additional trial assay using (NH4)2SO4, NH4Cl or NH4NO3 in the soil diminished the mean genetic diversity of nodule isolates by 41%, 33% and 26%, respectively. Rhizobium strains with genetic distances above 0.8 from the main R. etli group were infrequently encountered in bean nodules on plants with added fertilizer. Show more