Selection of nitrogen fixing rhizobia from uncultivated soils of Northern Argentina

PEDRO ALBERTO BALATTI, VIRGINIA MARTINEZ ALCÁNTARA, LAURA BALAGUE, GRACIELA PASTORINO, LILIANA VIDEIRA, DARIO SALVUCCI

Christopher S. Bond Life Sciences Center University of Missouri- Columbia, MO USA

Conferencia; The 21st North American Symbiotic Nitrogen Fixation Conference; 2010

Northern Argentina is part of a diversification center of species including many legumes such as Arachis spp., leguminous trees and others. Using different strategies we isolated rhizobia from these soils. We have evaluated the diversity of the bacteria captured by means of trap plants like promiscuous and improved American soybean cultivars and leguminous trees from 21 different sites. We found by means of ERIC and BOX PCR, 12 and 6 main patterns among the isolates that differed in their frequency of occurrence. Among 102 isolates that nodulate soybean, based on a multiplex reaction (Pastorino et al., 2003) we found that 88 were Bradyrhizobium strains that fix nitrogen, only three were fast growing Ensifer (Sinorhizobium) strains. Eleven isolates did not belong to any of these two groups. We also isolated rhizobia by means of inoculating cowpea plants, this isolates did not induced the developed of normal nodules on common bean and fix nitrogen at extremely low rate on soybean. Furthermore, based on physiological reactions were clustered separately from Bradryhizobium spp. Soybean isolates presented a different survival ability and are currently being selected based upon this and also on their ability to fix nitrogen.