Influence of bradyrhizobia location and movement on biological nitrogen fixation

BOGINO, P.; RIVAROLA DUARTE, L.; BANCHIO, E.; GIORDANO, W.

Mar del Plata, Buenos Aires

Congreso; XLIII Reunión Anual Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular; 2007

We previously reported that the lack of response to peanut inoculation in soils of Argentina may be due to the presence of a competitive indigenous population of rhizobia. In the present study, ERIC-PCR analysis of wild-type and native strains showed different electrophoretic patterns produced with ERIC primers.  The wild type strain C-145 (TAL-1371) and indigenous isolates each exhibited a unique profile, indicating that peanut nodulating rhizobia are highly diverse. Based on these results, we did field experiments in which the strain C-145 resistant to gentamicin at 80 ìg ml-1 (C-145 GmR) was inoculated in different ways so that distribution of strains was altered. This mutant provides a useful tool to evaluate nodule occupancy in soil environments since we confirmed that native strains are sensitive to gentamicin. Significant differences were observed in biological nitrogen fixation, such as nodule number, symbiotic effectiveness, nitrogenase activity and plant dry biomass for in-furrow inoculation compared to seed inoculation or control treatments. Nodule occupancy of the C-145 GmR strain was very high for in-furrow inoculation, indicating a positional advantage or movement into soil of in-furrow inoculated rhizobia for nodulation in peanut.