Search

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.

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]

Saline soil is a common problem in coastal paddy field, especially in Indonesia. Salinity affects rice growth and the activities of soil functional microbes, including functional bacteria, which play roles in plant growth. Some of these microbes are associated with rice plants and are able to survive under saline condition. The presence of functional microbes is also important to improve soil quality. Nitrogen and phosphate are essential soil nutrients and is available in soil due to the activities of nitrogen-fixing bacteria and free-living plant-associated bacteria. The objective of the present study was to obtain nitrogen-fixing, phosphate solubilizing and Indole Acetic Acid  (IAA)-producing bacteria that are able to survive and promote the growth of rice under saline conditions. From rice and peanut rhizosphere, Ca-phosphate (Ca-P) solubilizing and nitrogen-fixing bacteria were isolated separately using specific media. Then, the Ca-P solubilizing ability, phosphomonoesterase activity and IAA-producing ability were quantitatively examined. Based on the abilities, 20 strains were selected and identified as Burkholderia cepacia-complex, Burkholderia anthina, Burkholderia cenocepacia, Bacillus cereus-complex (three strains), Achromobacter spanius, Azospirillum sp. (four strains), Azotobacter sp. (three strains), Rhizobium leguminosarum, Rhizobium sp. (two strains), and Pseudomonas sp. (three strains). The inoculation of several single strains or the mixture of the selected strains promoted the growth of rice under saline conditions. These inoculants could be potential as biofertilizer in saline paddy fields.

O presente estudo objetivou avaliar a ocorrência de bactérias diazotróficas associadas ao sorgo, selecionar cultivares eficientes na associação com bactérias diazotróficas e identificar os isolados mais eficientes em fixar nitrogênio atmosférico (N²) e produzir ácido indol-acético (AIA). Utilizaram-se 14 cultivares de sorgo forrageiro em vasos, com dois níveis de N: 0 e 130kg ha-1 de N. A seleção de cultivares foi baseada na associação com bactérias diazotróficas e na eficiência de absorção de nitrogênio das cultivares. Para o isolamento das bactérias, foram utilizados diferentes meios de enriquecimento semi-sólido e, após o isolamento, foram quantificadas a produção de AIA e a quantidade de N² fixada pelos isolados. A ocorrência de bactérias diazotróficas foi constatada em todas as cultivares avaliados sendo que a distribuição das bactérias isoladas foi influenciada pelo genótipo da planta. Todos os isolados foram aptos em fixar N² e produzir AIA in vitro.The present study aimed to evaluate the occurrence of diazotrophic bacterial associated with sorghum plants, to select efficient sorghum cultivars associated with diazotrophic bacterial, as well as to identify isolates efficient on nitrogen fixation (N²) and indole acetic acid (IAA) production. Fourteen forage sorghum cultivars were cropped in jars under two levels of nitrogen fertilization: 0 and 130kg ha-1 of N. The selection of sorghum cultivars was based on the association with diazothophic bacterial and on the efficiency of nitrogen absorption. Semi-solid enrichment medium was used for the isolation of the diazotrophic bacterial. The occurrence of diazotrophics was verified in all cultivars of sorghum evaluated and, the distribution of the isolates was affected by the plant genotype. All the isolates were able to fix N² and to produce IAA in vitro.

In this study, we report on the isolation, identification, and characterization of seven fluorescent pseudomonads isolated from the roots, shoots, and rhizosphere soil of sugarcane and their impacts on the growth of sugarcane plantlets. 16S rRNA gene sequence of five isolates showed close homology with Pseudomonas putida, one with Pseudomonas graminis, and one with Pseudomonas fluorescens. Physiological and biochemical characterizations were determined using API50CH and QTS24 identification kits. The isolates were also subjected to tests for various known growth promoting properties including production of indole acetic acid, the ability to fix nitrogen via the presence of the nifH gene, and ability to solubilize phosphate. Biological control potential was determined from agar diffusion assays of HCN production and production of antifungal compounds against local isolates of Colletotrichum falcatum (that induces red-rot disease of sugarcane). Direct plant growth promoting effects were tested on sugarcane plantlets in tissue culture under gnotobiotic conditions. All seven isolates provided significant increases in fresh and dry masses but only five strains increased shoot height. [ABSTRACT FROM AUTHOR]