Effects of co-inoculation of native Rhizobium and Pseudomonas strains on growth parameters and yield of two contrasting Phaseolus vulgaris L. genotypes under Cuban soil conditions

Plant growth-promoting rhizobacteria (PGPR) have been isolated from legume nodules, displaying a potential to enhance nodulation, growth and yield of legume plants when co-inoculated with Rhizobium. This study genetically characterizes bacteria isolated from bean root nodules in Cuba and investigates the effect of Rhizobium-Pseudomonas co-inoculation on common bean (Phaseolus vulgaris L.) genotypes under two different Cuban soil conditions. Bacteria were identified by partial sequencing of the 16S rDNA gene. Growth-promoting effects of Rhizobium pisi-Pseudomonas monteilii co-inoculation were evaluated under field conditions in consecutive years. Two contrasting bean genotypes (BAT-477 and DOR-364) were co-inoculated and grown in two different soil types (Cambisol and Oxisol) in Cuban farm areas. Several growth parameters were evaluated at three time points during the crop cycle (21, 42 and 87 days after planting). In total, 20 strains were isolated belonging to six different genera, i.e. Arthrobacter, Chryseobacterium, Enterobacter, Stenotrophomonas, Pseudomonas and Rhizobium. It was observed that native Rhizobium-Pseudomonas co-inoculation as compared to single Rhizobium inoculation increased the nodulation, growth parameters and yield of the different genotypes. The response of BAT-477 was more pronounced than that of DOR-364. These findings contribute to the understanding of the interplay between Rhizobium, PGPR and the plant host under different soil conditions. Importantly, co-inoculation with R. pisi and P. monteilii could be an effective biofertilization strategy for common bean production.