Use of Azospirillum brasilense co-inoculated with rhizobia: alternative to enhance peanut yields

VICARIO, J.C., DARDANELLI, M.S., GIORDANO, W.

San Miguel de Tucumán

Congreso; VII congreso Argentino de Microbiología General (SAMIGE); 2011

SAMIGE

Bacteria of the family Rhizobiaceae interact with leguminous plants in a host-specific manner and form N2-fixing root nodules. On the other hand, bacteria of the genus Azospirillum are free-living, surface colonizing, sometimes endophytic diazotroph and plant growth promoting rhizobacteria (PGPR). They are capable of increasing the yield of important crops growing in various soils and climatic regions. 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. The experiments carried out in this work are in the context of a national project whose main goal is to optimize the symbiotic association between peanut/rhizobia using different co-inoculation methods. In this framework, it has to be provided that there are no problems of mutual exclusion, displacement, or competence between the inoculant strains. The aim of this research was to study the effect of co-inoculation of recommended and indigenous bradyrhizobia and a PGPR (Azospirillum brasilense Cd) on nodulation and symbiotic performance of peanut. There were inoculated at the time of transferring the pregerminated seeds with A. brasilense Cd at 1x106 CFU ml-1 and rhizobia strains 1x105 CFU ml-1. All values of root dry weight of inoculated peanut did not show significant changes with respect to the control conditions. A general positive effect on nodulation patterns number of nodules and growth was observed in the presence Azospirillum-PC34 strain co-inoculation. Co-inoculation with recommended bradyrhizobia (SEMIA6144 and TAL1000) and A. brasilense Cd caused a significant increase (80% and 50 % respectively) in the total number of nodules per plant by comparison with the number for plants treated with SEMIA6144 or TAL1000 alone. Possible mechanisms involved in the influence of A. brasilense on this symbiotic system will be discussed.