Plant growth-promoting potential of bacteria associated to pioneer plants from an active volcanic site of Chiapas (Mexico)

The use of microbial inoculants is an effective biotechnological alternative to increase crop productivity. In this work we studied the diversity of the Plant Growth Promoting Bacteria (PGPB) associated with pioneer plants that grow at the surroundings of the crater-lake of El Chichón volcano. Cheilanthes aemula (Pteridaceae) and Andropogon glomeratus (Poaceae) plants were dominant in this area. A total of 80 endophytes and 128 strains from the rhizosphere were isolated using selective culture media, and then characterized phenotypically. Isolates were tested for growth in high salt concentrations, at different pH and in moderate concentrations of heavy metals. The genetic diversity and identity of the strains were revealed by BOX_PCR and by sequencing of 16S rRNA gene. A. glomeratus isolates were classified within the genera Brevibacillus, Sinomonas, Sphingobium, Chryseobacterium, Pantoea, Ralstonia, Burkholderia, Serratia, Bacillus, Sphingomonas and Methylobacterium using 16S rDNA gene sequence analysis. C. aemula isolates were grouped into the genera Dyella, Burkholderia, Microbacterium, Enterobacter, Exiguobacterium, Pandoraea, Methylobacterium, Kocuria and Agrobacterium. The rhizospheric and endophytic strains were distinguished by their ability to produce different extracellular enzymes. The extremophile isolates had the ability to produce indole compounds (IAA), solubilize phosphate, synthesize siderophores, ACC deaminase and nitrogenase and showed a positive effect on the growth of Phaseolus vulgaris and upon the total content of nitrogen and phosphorus of plants. The diversity of bacteria associated to the pioneer plants had multifunctional qualities as PGPB that may contribute to their adaptation and proliferation at this active volcano and be used efficiently as biofertilizers to promote plant growth in organic farming systems