Inoculation method influences competitiveness and effectiveness of biological nitrogen fixation in the interaction peanut-rhizobia

BOGINO, P.; NIEVAS, F.; BANCHIO, E.; GIORDANO, W.

Villa Carlos Paz, Córdoba

Congreso; VI Congreso Argentino de Microbiología General; 2009

SAMIGE

Inoculation of legume plants with effective rhizobial strains constitutes a beneficial alternative in order to increase the productivity in these crops. Introduction of viable rhizobia into the agricultural ecosystems can be achieved by means of seed inoculation or by direct application into the soil, technology termed in furrow inoculation. The inoculation of the seedbed shows several advantages as compared to seed inoculation because it favors the survival and competitiveness of introduced strain. Arachis hypogaea L. (peanut) is one of the most important legume crops cultivated in the central area of Argentina. Inoculation of peanut is a controversial practice because nodulation by native bacteria is usually assumed to be sufficient. By using a laboratory model which makes possible to reproduce the application of seed inoculation or in furrow inoculation conditions, we evaluated the effect of these technologies on the efficiency of nitrogen fixation and competitiveness between the recommended as inoculant C-145 strain and indigenous strains. In furrow inoculation was found more effective than seed inoculation for the majority of the parameters of efficiency studied. It significantly increased weight and number of nodules, nitrogenase activity and shoot dry weight respect to seed inoculation. Competitiveness assays for nodule occupancy clearly showed the interference caused by native strains on the ability of a recommended strain to nodulate the legume, independently of the inoculation method applied. The effect was more marked for seed inoculation, C-145 strain inoculated on the seed was incapable of competing with native established strains which occupied the majority of nodules (90 %) independently of their localization on principal or lateral roots. For in furrow inoculation nodule occupancy by C-145 strain was slightly augmented when that strain increased its proportion in the inoculum. Results obtained for efficiency and competitiveness according the technique of inoculation applied, support the superior benefits that in furrow inoculation technology provides to an introduced recommended strain and finally to the legume crop.