Bacillus spp. are well known rhizosphere residents of many crops and usually show plant growth promoting (PGP) activities that include biocontrol capacity against some phytopatogenic fungi. Potato crops in the Andean Highlands of Peru face many nutritional and phytophatogenic problems that have a significant impact on production. In this context is important to investigate the natural presence of these microorganisms in the potato rhizosphere and propose a selective screening to find promising PGP strains. In this study, sixty three Bacillus strains isolated from the rhizosphere of native potato varieties growing in the Andean highlands of Peru were screened for in vitro antagonism against Rhizoctonia solani and Fusarium solani. A high prevalence (68%) of antagonists against R. solani was found. Ninety one percent of those strains also inhibited the growth of F. solani. The antagonistic strains were also tested for other plant growth promotion activities. Eighty one percent produced some level of the auxin indole-3-acetic acid, and 58% solubilized tricalcium phosphate. Phylogenetic analysis revealed that the majority of the strains belonged to the B. amyloliquefaciens species, while strains Bac17M11, Bac20M1 and Bac20M2 may correspond to a putative new Bacillus species. The results suggested that the rhizosphere of native potatoes growing in their natural habitat in the Andes is a rich source of Bacillus fungal antagonists, which have a potential to be used in the future as PGP inoculants to improve potato crop.

Several fast-growing strains nodulating Vicia faba in Peru, Spain and Tunisia formed a cluster related to Rhizobium leguminosarum . The 16S rRNA gene sequences were identical to that of R. leguminosarum USDA 2370^T, whereas rpoB, recA and atpD gene sequences were phylogenetically distant, with sequence similarities of less than 96 %, 97 % and 94 %, respectively. DNA–DNA hybridization analysis showed a mean relatedness value of 43 % between strain FB206^T and R. leguminosarum USDA 2370^T. Phenotypic characteristics of the novel strains also differed from those of the closest related species of the genus Rhizobium . Therefore, based on genotypic and phenotypic data obtained in this study, we propose to classify this group of strains nodulating Vicia faba as a novel species of the genus Rhizobium named Rhizobium laguerreae sp. nov. The type strain is FB206^T ( = LMG 27434^T = CECT 8280^T).

A group of strains isolated from root nodules of Phaseolus lunatus (Lima bean) in Peru were characterized by genotypic, genomic and phenotypic methods. All strains possessed identical 16S rRNA gene sequences that were 99.9 % identical to that of Bradyrhizobium lablabi CCBAU 23086^T. Despite having identical 16S rRNA gene sequences, the Phaseolus lunatus strains could be divided into two clades by sequence analysis of recA, atpD, glnII, dnaK and gyrB genes. The genome sequence of a representative of each clade was obtained and compared to the genomes of closely related species of the genus Bradyrhizobium . Average nucleotide identity values below the species circumscription threshold were obtained when comparing the two clades to each other (88.6 %) and with all type strains of the genus Bradyrhizobium (≤92.9 %). Phenotypes distinguishing both clades from all described and closely related species of the genus Bradyrhizobium were found. On the basis of the results obtained, two novel species, Bradyrhizobium paxllaeri sp. nov. (type strain LMTR 21^T = DSM 18454^T = HAMBI 2911^T) and Bradyrhizobium icense sp. nov. (type strain LMTR 13^T = HAMBI 3584^T = CECT 8509^T = CNPSo 2583^T), are proposed to accommodate the uncovered clades of Phaseolus lunatus bradyrhizobia. These species share highly related but distinct nifH and nodC symbiosis genes.