Analysis of cultivable endophytic bacteria in roots of maize in a soil from León Province in Mainland Spain

Abstract

In the present study, we isolated 14 bacterial strains from the roots of maize plants growing in a soil located at León (Spain). All these strains presented some of the following in vitro plant growth promotion mechanisms: (i) phosphate solubilization, (ii) ACC deaminase activity, (iii) siderophore and/or (iv) IAA production. These strains displayed 11 different RAPD profiles, showing they were genetically diverse. Representative strains from each RAPD type were identified on the basis of the 16S rRNA gene sequencing analysis, showing that most of them belonged to gamma-Proteobacteria and, specifically, to the families Enterobacteriaceae and Pseudomonadaceae (genus Pseudomonas). Most of the isolated strains belong to species that can be pathogenic for humans, such as Pantoea agglomerans, Pantoea ananatis, Lelliottia amnigena (formerly Enterobacter amnigenus), Kosakonia cowanii (formerly Enterobacter cowanii), Enterobacter ludwigii and Rahnella aquatilis, or for plants, such as Pseudomonas corrugata, Pseudomonas brassicacearum and Agrobacterium larrymoorei. These results showed the need of a correct identification of bacterial endophytes before selecting strains for the design of biofertilizers, which must be pathogen-free.