Screening, plant growth promotion and root colonization pattern of two rhizobacteria (Pseudomonas fluorescens Ps006 and Bacillus amyloliquefaciens Bs006) on banana cv. Williams (Musa acuminata Colla)

Banana is the second largest export crop in Colombia. To meet the demand of international markets, high amounts of chemical fertilizers are required, which represent high costs and can be hazardous to the environment. Plant growth promoting rhizobacteria (PGPR) can, at least partially, replace chemical fertilizers. In this paper, we evaluated the effect of nine PGPR of the genera Bacillus and Pseudomonas on banana growth. Banana seedlings were produced through tissue culture and acclimatized in the greenhouse core. Plants were inoculated with the rhizobacteria and growth parameters (plant height, leaf number, leaf area, pseudostem thickness, root and shoot fresh weight, root and shoot dry weight) were assessed after 55 days. The two best performing PGPR, Bs006 and Ps006 previously identified as Bacillus amyloliquefaciens and Pseudomonas fluorescens, respectively, promoted banana growth similarly or even slightly superior to 100% chemical fertilization, and were selected for further characterization of root colonization by both eletron microscopy and confocal microscopy of fluorescence in situ hybridization (FISH)-stained root tissues. Both P. fluorescens Ps006 and B. amyloquifaciens Bs006 showed ability to colonize banana roots, but Bs006 appeared faster than Ps006 in the colonization dynamics. This work demonstrated that inoculation of rhizobacteria Bacillus amyloliquefaciens Bs006 and Pseudomonas fluorescens Ps006 could partially replace the chemical fertilization of tissue cultured banana plants, and therefore could be used for the formulation of a new biofertilizer.