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In the present study, native root-knot nematode antagonistic rhizobacteria i.e., Microbacterium laevaniformansMlIRh3, Staphylococcus kloosiiSkIRh4, and Priestia aryabhattai PaIRh7 from Meloidogyne incognita infected and Staphylococcus sciuri SsHRh3, Bacillus pumilus BpHRh5, Priestia megaterium PmHRh10 from uninfected tomato plants grown in the protected structure were characterized for their key plant growth promotion traits and survivability in soil, viz. phosphate solubilization activity, indole acetic acid production, ammonia production, and substrate utilization profiles. Among rhizobacteria, S. sciuri SsHRh3, B. pumilus BpHRh5, P. megaterium PmHRh10, M. laevaniformans MlIRh3, and S. kloosii SkIRh4 showed phosphate solubilisation activities on Pikovaskaya's media. In the presence of tryptophan, the rhizobacteria P. megaterium PmHRh10, M. laevaniformans MlIRh3, and P. aryabhattai PaIRh7 produced indole acetic acid. Similarly, S. sciuri SsHRh3, B. pumilus BpHRh5, P. megaterium PmHRh10, S. kloosii SkIRh4, and P. aryabhattai PaIRh7 produced ammonia under laboratory conditions. Among the 35 substrates studied, rhizobacteria had different substrate utilization profiles,S. sciuri SsHRh3 utilized most of the substrates (18), followed by P. aryabhattai PaIRh7, S. kloosiiSkIRh4, M. laevaniformansMlIRh3, B. pumilus BpHRh5 and P. megaterium PmHRh10which were able to use 17, 16, 15, 14 and 13 substrates, respectively. Furthermore, the application of these rhizobacterial isolates either singly or in consortia revealed that a consortium of all three rhizobacterial isolates i.e., SsHRh3 + BpHRh5 + PmHRh10 from nematode uninfested rhizosphere shown highest plant growth promotion activity compared untreated control and singly application. In contrast, S. kloosiiSkIRh4 either singly or in consortia, no significant effect on plant growth was observed under the pot experiment. Overall, the study found that root-knot nematode antagonistic rhizobacterial isolates were a promising candidate for plant growth promotion activity. Using them alone or in combination can be a safe alternative to synthetic chemical nematicides for suppression of root-knot nematode incidence in tomatoes grown under protected environments. [ABSTRACT FROM AUTHOR]

Salt stress caused by sodic soils is an important constraint that impacts the production of crucial solanaceous vegetable crops globally. Halotolerant poly-extremophiles rhizobacteria can inhabit hostile environments like salinity, drought, etc. The present study was aimed to design a halotolerant micro-formulation using highly salt-tolerant bacterial strains previously isolated from salt-tolerant rice and wheat rhizosphere in sodic soil. Nine halotolerant isolates were examined for plant growth-promoting traits and biomass production in pot studies with sodic soil of pH 9.23 in tomato. Compatible, efficient isolates were aimed to be formulated into different consortia like PGPR-C1, PGPR-C2 and, PGPR-C3 for field evaluation in sodic soils of pH 9.14. Halotolerant rhizobacterial consortia (PGPR-C3) comprising Lysinibacillus spp. and Bacillus spp. were found to produce extracellular enzymes like amylase, protease, cellulase, and lipase, showing significantly enhanced vegetative parameters, yield and lycopene content of tomato hybrid NS585 under salt-stressed sodic soils. PGPR-C3 consortia also showed enhanced plant growth-promoting activities and halo tolerance like high Indole acetic acid production, 1-aminocyclopropane-1-carboxylic acid deaminase, and antioxidative enzyme activity over the uninoculated control. Further, inoculation with PGPR-C3 consortia resulted in the efficient exclusion of Na+ ions from the rhizosphere through increased absorption of K+. Results of the study reveal that inoculation with PGPR-C3 consortia could alleviate the salt stress and promotes the successful cultivation of tomato crop in sodic soils. It can be considered the best option for eco-friendly, sustainable cultivation of vegetables like a tomato in sodic soils with a high pH range of up to 9.14. [ABSTRACT FROM AUTHOR]

Plant growth promoting (PGP) activities of soil bacteria directly help plants in taking up the nutrients, attuning the growth hormones and indirectly safeguard by inhibiting diverse groups of fungal pathogens. In this study, we explored the native P solubilizing bacteria (PSB) isolated from the acid soils (pH < 5.5) of Odisha for selection of efficient PGPR with antifungal potential. Five PSB strainswere checked for their P solubilization efficiencies with Ca3(PO4)2,AlPO4,FePO4 and Fe3(PO4)2. The bioconversion of P by all the five strains in the broth medium followed the order Ca-P > Fe(III)-P > Fe(II)-P > Al-P. The strains interestingly showed potential plant growthpromoting properties including indole acetic acid (IAA) and siderophore production in in vitro tests. These five strains also exhibited antifungal activities against fungal pathogens (Pythium aphanidermatum, Fusarium oxysporum, Pythium debaryanum, Thanatephorus cucumeris and Aspergillus niger) of groundnut. A field study was carried out with two of the above PSB strains [identified as Bacillus amyloliquefaciens (KT633845) and Burkholderia cepacia (KT717633)] with groundnut. Both the stains significantly influenced the plant growth (plant height, nodule no. and nodule dry weight) and pod yield. However, these two strains inoculated along with doses of inorganic phosphate (SSP, single super phosphate) resulted in significantly higher pod yield as well as residual soil P. Additionally; the prevalence of both seedling mortality and plant mortality due to collar rot and stem rot were found to be reduced significantly in the inoculated plots. The findings substantiate the growth promoting ability of the two P solubilizing strains, and thus qualifies to be used as biofertilizers either alone or as components of INM practices. [ABSTRACT FROM AUTHOR]

The implementation of sustainable agriculture encompasses practices enhancing the activity of beneficial soil microorganisms, able to modulate biogeochemical soil cycles and to affect soil fertility. Among them, arbuscular mycorrhizal fungi (AMF) establish symbioses with the roots of most food crops and play a key role in nutrient uptake and plant protection from biotic and abiotic stresses. Such beneficial services, encompassing improved crop performances, and soil resources availability, are the outcome of the synergistic action of AMF and the vast communities of mycorrhizospheric bacteria living strictly associated with their mycelium and spores, most of which showing plant growth promoting (PGP) activities, such as the ability to solubilize phosphate and produce siderophores and indole acetic acid (IAA). One of the strategies devised to exploit AMF benefits is represented by the inoculation of selected isolates, either as single species or in a mixture. Here, for the first time, the microbiota associated with a commercial AMF inoculum was identified and characterized, using a polyphasic approach, i.e., a combination of culture-dependent analyses and metagenomic sequencing. Overall, 276 bacterial genera were identified by Illumina high-throughput sequencing, belonging to 165 families, 107 orders, and 23 phyla, mostly represented by Proteobacteria and Bacteroidetes. The commercial inoculum harbored a rich culturable heterotrophic bacterial community, whose populations ranged from 2.5 to 6.1 × 106 CFU/mL. The isolation of functional groups allowed the selection of 36 bacterial strains showing PGP activities. Among them, 14 strains showed strong IAA and/or siderophores production and were affiliated with Actinomycetales (Microbacterium trichotecenolyticum, Streptomyces deccanensis/scabiei), Bacillales (Bacillus litoralis, Bacillus megaterium), Enterobacteriales (Enterobacter), Rhizobiales (Rhizobium radiobacter). This work demonstrates for the first time that an AMF inoculum, obtained following industrial production processes, is home of a large and diverse community of bacteria with important functional PGP traits, possibly acting in synergy with AMF and providing additional services and benefits. Such bacteria, available in pure culture, could be utilized, individually and/or in multispecies consortia with AMF, as biofertilizers and bioenhancers in sustainable agroecosystems, aimed at minimizing the use of chemical fertilizers and pesticides, promoting primary production, and maintaining soil health and fertility. [ABSTRACT FROM AUTHOR]

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