ENDOPHYTIC OCCUPATION OF PEANUT ROOT NODULES BY OPPORTUNISTIC GAMMAPROTEOBACTERIA

IBÁÑEZ, F.,; ANGELINI,J.; TAURIAN,T.; TONELLI,M.L.; FABRA, ADRIANA

SYSTEMATIC AND APPLIED MICROBIOLOGY

ELSEVIER GMBH

Año: 2009 vol. 189 p. 345 - 356

0723-2020

Several bacterial isolates were recovered from surface-sterilized root nodules of Arachis hypogaea L. (peanut) plants growing in soils from Co´rdoba, Argentina. The 16S rDNAsequences of seven fast-growing strains were obtained and the phylogenetic analysis showed that these isolates belonged to the Phylum Proteobacteria, Class Gammaproteo- bacteria, and included Pseudomonas spp., Enterobacter spp., and Klebsiella spp. After storage,these strains became unable to induce nodule formation in Arachis hypogaea L. plants,but they enhanced plant yield.When the isolates were co-inoculated with an infective Bradyrhizobium strain,they were even found colonizing pre-formed nodules. Analysis of symbiotic genesshowedthatthe nifH gene wasonlydetectedforthe Klebsiella-like isolates and the nodC gene could not be amplified by PCR or be detected by Southern blotting in any of the isolates.The results obtained support the idea that these isolates are opportunistic bacteria able tocolonize nodules induced by rhizobia.  Keywords: Arachis hypogaea; Bradyrhizobium; Pseudomonas; Klebsiella; Enterobacter; Endophytes from nodules