title: Multifunctionality and diversity of culturable bacterial communities strictly associated with spores of the plant beneficial symbiont Rhizophagus intraradices.
abstract: Arbuscular Mycorrhizal Fungi (AMF) live in symbiosis with most crop plants and represent essential elements of soil fertility and plant nutrition and productivity, facilitating soil mineral nutrient uptake and protecting plants from biotic and abiotic stresses. These beneficial services may be mediated by the dense and active spore-associated bacterial communities, which sustain diverse functions, such as the promotion of mycorrhizal activity, biological control of soilborne diseases, nitrogen fixation, and the supply of nutrients and growth factors. In this work, we utilised culture-dependent methods to isolate and functionally characterize the microbiota strictly associated to Rhizophagus intraradices spores, and molecularly identified the strains with best potential plant growth promoting (PGP) activities by 16S rDNA sequence analysis. We isolated in pure culture 374 bacterial strains belonging to different functional groups-actinobacteria, spore-forming, chitinolytic and N2-fixing bacteria-and screened 122 strains for their potential PGP activities. The most common PGP trait was represented by P solubilization from phytate (69.7%), followed by siderophore production (65.6%), mineral P solubilization (49.2%) and IAA production (42.6%). About 76% of actinobacteria and 65% of chitinolytic bacteria displayed multiple PGP activities. Nineteen strains with best potential PGP activities, assigned to Sinorhizobium meliloti, Streptomyces spp., Arthrobacter phenanthrenivorans, Nocardiodes albus, Bacillus sp. pumilus group, Fictibacillus barbaricus and Lysinibacillus fusiformis, showed the ability to produce IAA and siderophores and to solubilize P from mineral phosphate and phytate, representing suitable candidates as biocontrol agents, biofertilisers and bioenhancers, in the perspective of targeted management of beneficial symbionts and their associated bacteria in sustainable food production systems.
authors.affiliation: Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Battini
authors.affiliation: Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy.
authors.forename: Caterina
authors.initials: C
authors.lastname: Cristani
authors.affiliation: Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy.
authors.forename: Manuela
authors.initials: M
authors.lastname: Giovannetti
authors.affiliation: Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy. Electronic address: monica.agnolucci@unipi.it.
authors.forename: Monica
authors.initials: M
authors.lastname: Agnolucci
mesh_terms: D039903:Actinobacteria / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D001407:Bacillus / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D001419:Bacteria / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D001483:Base Sequence; D044822:Biodiversity; D061046:Biological Control Agents; D018556:Crops, Agricultural / Q000382:microbiology; D004275:DNA, Ribosomal / Q000235:genetics; D005308:Fertilizers / Q000382:microbiology; D055137:Glomeromycota / Q000502:physiology*; D007210:Indoleacetic Acids / Q000378:metabolism; D038821:Mycorrhizae / Q000502:physiology; D009586:Nitrogen Fixation; D010088:Oxidoreductases / Q000235:genetics; D010937:Plant Growth Regulators / Q000378:metabolism; D010944:Plants / Q000382:microbiology*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017262:Siderophores / Q000096:biosynthesis; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D013172:Spores, Fungal; D013559:Symbiosis
chemical_list: D061046:Biological Control Agents; D004275:DNA, Ribosomal; D005308:Fertilizers; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D012336:RNA, Ribosomal, 16S; D017262:Siderophores; D012987:Soil; D010088:Oxidoreductases; C029130:nitrogenase reductase
keywords: AMF spores; Culturable spore-associated bacteria; Plant growth promoting bacteria; Rhizophagus intraradices