The Effect of Phylogenetically Different Bacteria on the Fitness of Pseudomonas fluorescens in Sand Microcosms

In most environments many microorganisms live in close vicinity and can interact in various ways. Recent studies suggest that bacteria are able to sense and respond to the presence of neighbouring bacteria in the environment and alter their response accordingly. This ability might be an important strategy in complex habitats such as soils, with great implications for shaping the microbial community structure. Here, we used a sand microcosm approach to investigate how Pseudomonas fluorescens Pf0-1 responds to the presence of monocultures or mixtures of two phylogenetically different bacteria, a Gram-negative (Pedobacter sp. V48) and a Gram-positive (Bacillus sp. V102) under two nutrient conditions. Results revealed that under both nutrient poor and nutrient rich conditions confrontation with the Gram-positive Bacillus sp. V102 strain led to significant lower cell numbers of Pseudomonas fluorescens Pf0-1, whereas confrontation with the Gram-negative Pedobacter sp. V48 strain did not affect the growth of Pseudomonas fluorescens Pf0-1. However, when Pseudomonas fluorescens Pf0-1 was confronted with the mixture of both strains, no significant effect on the growth of Pseudomonas fluorescens Pf0-1 was observed. Quantitative real-time PCR data showed up-regulation of genes involved in the production of a broad-spectrum antibiotic in Pseudomonas fluorescens Pf0-1 when confronted with Pedobacter sp. V48, but not in the presence of Bacillus sp. V102. The results provide evidence that the performance of bacteria in soil depends strongly on the identity of neighbouring bacteria and that inter-specific interactions are an important factor in determining microbial community structure.     

Fe and P Solubilization Under Limiting Conditions by Bacteria Isolated from Carex kobomugi Roots at the Hasaki Coast

Our objective was simply to report a sedge species, Carex kobomugi Ohwi that has beneficial bacterial associations under low Fe and P conditions of the Hasaki coast, Japan. C. kobomugi is the dominant species in our study area and grows closest to the sea. C. kobomugi showed higher Fe and P content, while these nutrients were less available under alkaline root-zone soil. Within the roots, mycorrhizal fungal colonization was absent, and endophytic fungal colonization was low. On the contrary, endophytic bacteria (e.g. Bacillus sp., Streptomyces luteogriseus, and Pseudomonas fluorescens) were isolated, which exhibited both siderophore production and inorganic phosphate solubilization under Fe or P limited conditions. Our results suggest that colonization of root tissue by these bacteria contribute to the Fe and P uptakes by C. kobomugi by increasing availability in the soil.     

Antimicrobial potentials of endophytic fungi residing in <Emphasis Type="Italic">Quercus variabilis</Emphasis> and brefeldin A obtained from <Emphasis Type="Italic">Cladosporium</Emphasis> sp.

Among 67 endophytic fungi isolated from Quercus variabilis, 53.7% of endophytic fungal fermentation broths displayed growth inhibition on at least one test microorganism, such as pathogenic fungi (Trichophyton rubrum, Candida albicans, Aspergillus niger, Epidermophyton floccosum, Microsporum canis) and bacteria (Escherichia coli, Bacillus subtilis, Pseudomonas fluorescens). Moreover, 19.4% of strains showed a broader antimicrobial spectrum, such as Aspergillus sp., Penicillium sp., Alternaria sp., 20.9% of strains showed strong inhibition (+++) to pathogenic bacteria, while only 7.5% displayed that to test fungi. The most active antifungal strain I(R)9-2, Cladosporium sp. was selected and fermented. From the broth, a secondary metabolite, brefeldin A was obtained. This is the first report on the antimicrobial potentials of endophytic fungi residing in Q. variabilis and isolation of brefeldin A produced by Cladosporium sp.     

Combinatorial effect of endophytic and plant growth promoting rhizobacteria against wilt disease of Capsicum annum L. caused by Fusarium solani

Combination of biocontrol agents that are compatible with each other is a strategic approach to control the plant disease and pest. The present study was designed to evaluate the protective effects of compatible endophytic bacterial strains (Bacillus subtilis; EPCO16 and EPC5) and rhizobacterial strain (Pseudomonas fluorescens; Pf1) against chilli wilt disease caused by Fusarium solani. Our results showed that B. subtilis (EPCO16 and EPC5) and P. fluorescens (Pf1) were compatible and effectively inhibited the growth of the F. solani. The application of endophytic and rhizobacterial strains, singly and in combination in green house and field conditions were found to be effective in controlling the chilli Fusarium wilt disease by inducing systemic resistance (ISR) as evidenced by enhanced activities of PO, PPO, PAL, β-1,3-glucanase, Chitinase and Phenolic involved in the synthesis of phytolaexins thereby promoting the growth of plants. However, combinations of EPCO16 + EPC5 + Pf1 bacterial strains were more effective than single agents. These findings suggest that synergistic interactions of biocontrol agents may be responsible for the management of chilli wilt disease caused by F. solani.     

Effect of Pseudomonas fluorescens RB4 and Bacillus subtilis 189 on the phytoremediation potential of Catharanthus roseus (L.) in Cu and Pb-contaminated soils

The remediation of heavy metal-contaminated soils has become a critical issue due to toxic effects of these metals on living organisms. The current research was conducted to study the effect of Pseudomonas fluorescens RB4 and Bacillus subtilis 189 on the growth and phytoremediation potential of Catharanthus roseus in Cu- and Pb-contaminated soils. The bacterial strains exhibited significantly higher level of water-extractable Pb and Cu in Pb, Cu, and Cu+Pb-contaminated. The P. fluorescens RB4 inoculated plants, produced 102%, 48%, and 45% higher fresh weight (FW) in soils contaminated with Cu, Pb, and both elements, respectively, as compared to un-inoculated control plants. Similarly, B. subtilis 189 inoculated plants produced 108%, 43%, and 114% more FW in the presence of Cu, Pb, and both elements. The plants co-cultivated with both bacteria exhibited 121%, 102%, and 177% higher FW, in Cu, Pb, and both elements contaminated soils, as compared to respective un-inoculated control. Co-cultivation of P. fluorescens RB4, B. subtilis 189, and P. fluorescens RB4 + B. subtilis 189 resulted in higher accumulation of Cu and Pb in shoots of the C. roseus grown in contaminated soils as compared to un-inoculated control. Bacterial treatments also improved the translocation and metal bioconcentration factors. The growth and phytoextraction capability of C. roseus was improved by inoculation of P. fluorescens RB4 and B. subtilis 189.     

Plant growth promoting bacteria enhance water stress resistance in green gram plants

Plant growth promoting bacterial (PGPB) strains Pseudomonas fluorescens Pf1 and endophytic Bacillus subtilis EPB5, EPB22, EPB 31 were tested for their capacity to induce water stress related proteins and enzymes in green gram (Vigna radiata) plants. Among the different bacteria used, P. fluorescens Pf1 increased the vigour index, fresh weight and dry weight of green gram seedlings in vitro. Quantitative and qualitative analyses of stress-related enzymes indicated the greater activity of catalase and peroxidase in green gram plants bacterized with P. fluorescens Pf1 against water stress when compared to untreated plants. The greater accumulation of proline was recorded in Pf1 treated plants compared to untreated plants. The pot culture study revealed the greater resistance to water stress by green gram plants treated with P. fluorescens Pf1 compared to untreated plants. The greater activity of stress-related enzymes in green gram plants mediated by PGPB could pave the way for developing drought management strategies.     

Plant growth promoting rhizobacteria improve growth and essential oil yield in Origanum majorana L.

Effects of root colonization by plant growth promoting rhizobacteria (PGPR) on biomass, and qualitative and quantitative composition of essential oils, were determined in the aromatic crop Origanum majorana L. (sweet marjoram). PGPR strains evaluated were Pseudomonas fluorescens, Bacillus subtilis, Sinorhizobium meliloti, and Bradyrhizobium sp. Only P. fluorescens and Bradyrhizobium sp. showed significant increases in shoot length, shoot weight, number of leaf, number of node, and root dry weight, in comparison to control plants or plants treated with other PGPR. Essential oil yield was also significantly increased relative to non-inoculated plants, without alteration of oil composition. P. fluorescens has clear commercial potential for economic cultivation of O. majorana.     

Effect and mechanism of endophytic bacteria on growth and secondary metabolite synthesis in Salvia miltiorrhiza hairy roots

Our study found that except Novosphingobium resinovorum (B5) Salvia miltiorrhiza root endophytic bacteria Pseudomonas brassicacearum sub sp. neoaurantiaca (B1), Rhizobium radiobacter (B2), Pseudomonas thivervalensis (B3), Pseudomonas frederiksbergensis (B4) significantly improved the activity of key enzymes 3-hydroxy-3-methyglutary1-CoA reductase and 1-deoxy-d-xylulose-5-phosphate synthase in the biosynthetic pathway of tanshinones. Specifically, HMGR activity with B1 treatment increased 2.1-fold that of control, 1-deoxy-d-xylulose-5-phosphate synthase activity with B2 treatment increased 5.0-fold that of control, which caused a significant increase in tanshinone content in the hairy roots. The dihydrotanshinone I and cryptotanshinone content under B1 treatment increased 19.2-fold and 11.3-fold, respectively, and total tanshinone content increased 3.7-fold that of control. The five endophytic bacteria B1, B2, B3, B4 and B5 all significantly decreased phenylalanine ammonia-lyase and tyrosine aminotransferase activity in hairy roots, of which, B3 treatment decreased phenylalanine ammonia-lyase activity by 46.2 %, and B2 treatment decreased tyrosine aminotransferase activity by 44.7 % compared with the control. Each of the five endophytic bacteria decomposed rosmarinic acid and salvianolic acid B, which caused a significant decrease in rosmarinic acid and salvianolic acid B content in hairy roots, with B2 treatment decreasing rosmarinic acid and salvianolic acid B content by 94.5 and 89.0 %, respectively, compared with the control. The five endophytic bacteria also inhibited the growth of S. miltiorrhiza hairy roots, of which, B2 and B4 treatment decreased hairy root biomass by 55.2 and 51.3 %, respectively, compared with the control, while hairy roots promoted the growth of B4 and B5 and inhibited the growth of B1 and B3.     

Functional evaluation of culture filtrates of Bacillus subtilis and Pseudomonas fluorescens on the mortality and hatching of Meloidogyne javanica

Rhizospheric bacteria Bacillus subtilis and Pseudomonas fluorescens are two widely tested biological control agents against root-knot nematodes (RKN) of different crops. However, their performance as bio-control agents varies with their place of origin. Culture filtrates of rhizospheric bacteria contain some intermediary metabolites that have nematicidal activity. An in vitro experiment was undertaken to evaluate the functionality of culture filtrates of B. subtilis (MN252542.1) and P. fluorescens (MN256394.1) at different concentrations (1.0%, 2.5%, 5.0%, 7.0%, 10.0% and 25.0%) on the hatching and mortality of Meloidogyne javanica at different time span. Bacterial strains were isolated from rhizospheric soils of Bangladesh. At three days after incubation (DAI), 25.0% concentration of culture filtrates of both B. subtilis and P. fluorescens showed 100.0% mortality of second stage juveniles (J₂) of M. javanica. Additionally, 25.0% concentration of culture filtrates of both bacteria showed 100.0% inhibition of hatching at one week after incubation (WAI). A decreasing trend in hatching of M. javanica was observed with the increment of the concentration of culture filtrates and progression of incubation time. The findings of this experiment reveal that culture filtrates of these accessions of B. subtilis and P. fluorescens are effective for controlling M. javanica and would be potential candidates for developing bio-nematicides.     

Biopriming of micropropagated banana plants at pre- or post-BBTV inoculation stage with rhizosphere and endophytic bacteria determines their ability to induce systemic resistance against BBTV in cultivar Grand Naine

ABSTRACT

Rhizospheric and endophytic bacteria isolated from the roots and corms of banana were tested to find out their efficiency in controlling against banana bunchy top virus (BBTV). Bioformulations of mixtures of endophytic Bacillus pumilus and B. subtilis isolated from banana cv. Grand Naine and rhizobacterial isolate Pseudomonas fluorescens (Pf1) were found to be effective in increasing the growth and physiological parameters such as pseudostem girth and height, number of leaves, phyllochron, and leaf area in biohardened plants under greenhouse study. The consortia of bioformulation mixture of B. pumilus, B. subtilis, and P. fluorescens I showed 61.62% disease reduction over control. The defence enzymes such as peroxidase (POX), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), and total phenol were induced to an elevated level in biohardened plants. The applications of bioformulations to plants led to delay the symptom expression for 63.75 to 70.50 days compared to control after challenge inoculation with the virus in 34–67% of plants that exhibited the symptoms till 150 DAI. However, biohardening of plants with the same combinations of bacteria three days after BBTV inoculation led to express the symptoms 29.16 to 36.71 days and there was a significant decrease in plant growth parameters. Biopriming prior to BBTV infection has attributed to the enhanced plant growth and resistance against BBTV whereas, the same treatments after virus inoculation did not induce resistance. This study has proved that the time of application of consortia of bio-inoculants determines their effect of induced resistance to BBTV in micropropagated plants.     

Effects of nematodes,fungi and bacteria on the growth of young apple trees grown in apple replant disease soil

Growth, dry root weight of seedlings and root score of apple seedlings cv. McIntosh were reduced when soils were inoculated with Pratylenchus penetrans, Penicillium janthinellum, Constantinella terrestris, Trichoderma sp., and 4 strains of Bacillus subtilis. Trichoderma sp., and B-1 and B-26 strains of B. subtilis alone reduced plant growth but the combination of Trichoderma sp. + B. subtilis (B-1) and Trichoderma sp. + B. subtilis (B-26) increased plant height. Plant height, root weight and root score were significantly reduced when P. penetrans plus B. subtilis or P. penetrans plus fungi plus bacteria were present in the soil. It is suggested that fungi, bacteria, nematodes alone or their combinations such as nematodes plus bacteria or nematodes plus fungi plus bacteria may contribute towards the occurrence of apple replant disease.Contribution number 700.Contribution number 700.     

Defense Responses and Changes in Symbiotic Gut Microflora in the Colorado Potato Beetle <Emphasis Type="Italic">Leptinotarsa decemlineata</Emphasis> under the Effect of Endophytic Bacteria from the Genus Bacillus

Phytophagous insects and host plants have a complex of microsymbionts and make up a united co-evolving system with them. Microsymbiotic complexes are actively involved in stress responses of macrosymbionts. We established that a treatment of potato plants with endophytic bacterial strains Bacillus thuringiensis var. thuringiensis-5689, B. th. var. kurstaki-5351, and Bacillus subtilis 26D decreased the survival rate of the plant feeder, Colorado potato beetle Leptinotarsa decemlineata Say. The B. th. strains suppressed phenoloxidase and acetylcholinesterase activities in the beetle hemolymph. An antagonistic relationship was found between endophytic bacteria B. subtilis 26D and beetle symbiotic bacteria from the genera Acinetobacter and Enterobacter, with the former being able to suppress the growth of endophytic colonies. The recombinant B. subtilis strain 26D Cry, containing the B. th. var. kurstaki δ-endotoxin cry1Ia gene, combined the ability of the original B. subtilis 26D strain to suppress the development of beetle symbionts and immune responses with a production of the Cry toxin, thus leading to a high mortality of the phytophage.     

Root-knot Nematode Problem of Some Winter Ornamental Plants and Its Biomanagement

A microplot study under field conditions was carried out during 2 consecutive years to assess the effect of root-knot nematode infection (2,000 Meloidogyne incognita eggs/kg soil) on three winter ornamental plants: hollyhock (Althea rosea), petunia (Petunia hybrida), and poppy (Papaver rhoeas). Effects of root-dip treatment with the biocontrol agents Pochonia chlamydosporia, Bacillus subtilis, and Pseudomonas fluorescens and the nematicide fenamiphos were tested. The three ornamental species were highly susceptible to M. incognita, developing 397 and 285 (hollyhock), 191 and 149 (petunia), and 155 and 131 (poppy) galls and egg masses per root system, respectively, and exhibited 37% (petunia), 29% (poppy), and 23% (hollyhock) (P = 0.05) decrease in the flower production. Application of fenamiphos, P. chlamydosporia, P. fluorescens, and B. subtilis suppressed nematode pathogenesis (galls + egg masses) by 64%, 37%, 27%, and 24%, respectively, leading to 14% to 29%, 7% to 15%, 14% to 36%, and 7% to 33% increase in the flower production of the ornamental plants, respectively. Treatment with P. fluorescens also increased the flowering of uninfected plants by 11% to 19%. Soil population of M. incognita was decreased (P = 0.05) due to various treatments from 2 months onward, being greatest with fenamiphos, followed by P. chlamydosporia, B. subtilis, and P. fluorescens. Frequency of colonization of eggs, egg masses, and females by the bioagents was greatest by P. chlamydosporia, i.e., 25% to 29%, 47% to 60%, and 36% to 41%, respectively. Colonization of egg masses by B. subtilis and P. fluorescens was 28% to 31% and 11% to 13%, respectively, but the frequency was 0.3% to 1.3% in eggs. Rhizosphere population of the bioagents was increased (P = 0.05) over time, being usually greater in the presence of nematode.     

Bioactivity of endophytic Trichoderma fungal species from the plant family Cupressaceae

Trichoderma fungal species are universal soil residents that are also isolated from decaying wood, vegetables, infected mushroom and immunocompromised patients. Trichoderma species usually biosynthesize a plethora of secondary metabolites. In an attempt to explore endophytic fungi from healthy foliar tissues of the plant family Cuppressaceae, we explored Cupressus arizonica, C. sempervirens var. cereiformis, C. sempervirens var. fastigiata, C. sempervirens var. horizontalis, Juniperus excelsa, Juniperus sp. and Thuja orientalis plants and recovered several endophytic Trichoderma fungal strains from Trichoderma atroviride and Trichoderma koningii species. We found that the host plant species and biogeographical location of sampling affected the biodiversity and bioactivity of endophytic Trichoderma species. Furthermore, the bioactivity of Trichoderma isolates and the methanol extracts of their intra- and extra-cellular metabolites were assessed against a panel of pathogenic fungi and bacteria. Fungal growth inhibition, conidial cytotoxicity, minimum inhibitory concentration and minimum bactericidal concentration were evaluated and analyzed by statistical methods. Our data showed that both intra- and extracellular secondary metabolites from all endophytic isolates had significant cytotoxic and antifungal effects against the model target fungus Pyricularia oryzae and the cypress fungal phytopathogens Diplodia seriata, Phaeobotryon cupressi and Spencermartinsia viticola. Further research indicated their significant antimicrobial bioactivity against the model phytopathogenic bacteria Pseudomonas syringae, Erwinia amylovora and Bacillus sp., as well. Altogether, the above findings show for the first time the presence of T. atroviride and T. koningii as endophytic fungi in Cupressaceae plants and more importantly, the Trichoderma isolates demonstrate significant bioactivity that could be used in future for agrochemical/drug discovery and pathogen biocontrol.     

Application of endophytic bacteria for controlling anthracnose disease (Colletotrichum lindemuthianum) on bean plants

Over 100 endophytic bacterial isolates were isolated from surface-sterilised roots of the Fabaceae family in East Azerbaijan farms. These isolates were screened for their in vitro biocontrol activity against Colletotrichum lindemuthianum by dual culture technique using potato dextrose agar (PDA) medium. Eight bacterial isolates (Bacillus subtilis subsp. subtilis, Bacillus atrophaeus, B. tequilensis, B. subtilis subsp. spizizenii, Streptomyces cyaneofuscatus, S. flavofuscus, S. parvus, S. acrimycini) showed promising inhibition on mycelial growth of C. lindemuthianum , and thus, these isolates were selected for greenhouse experiments. The disease control rate using these selected endophytic bacteria was varied from 40 to 76.80% in greenhouse without any negative effects on different growth performance, suggesting that these selected endophytic bacteria are potential to be developed as biocontrol agents.     

Evaluation of a liquid formulation of Pseudomonas fluorescens against Fusarium oxysporum f. sp. cubense and Helicotylenchus multicinctus in banana plantation

Plant growth promoting rhizobacteria (PGPR) are eco-friendly alternatives to chemical fungicides to manage plant diseases. We evaluated the efficacy of a Pseudomonas fluorescens formulation against Fusarium oxysporum f. sp. cubense and Helicotylenchus multicinctus at multiple banana plantations. Three field trials were conducted to assess the wilt incidence and the populations of nematode and bacteria in the soil treated with a liquid formulation of P. fluorescens at 2.0, 3.0 and 4.0 l ha^?1 using drip irrigation system at 60, 120, 180 and 240 days after planting. The results showed that the treatment at 4.0 l ha^?1 reduced the wilt incidence by 60 %. It also reduced the overall population of H. multicinctus by 41.3–89.0 % in the treated fields. The presence of P. fluorescens in the treated soil was 5.6 × 10⁶ cfu g^?1 of soil at the time of harvest. The treatment of biocontrol agent P. fluorescens also resulted in an overall yield increase in banana production by 36.6–46.5 % compared to the control.     

Using Phospholipid Fatty Acid Technique to Study Short-Term Effects of the Biological Control Agent Pseudomonas fluorescens DR54 on the Microbial Microbiota in Barley Rhizosphere

The biological control agent (BCA) Pseudomonas fluorescens DR54 was applied to seeds (experiment 1) or roots (experiment 2) of barley growing in microcosms, while noninoculated plants served as controls. The fate of the BCA and its effects on the rhizosphere microbial community was evaluated in microcosms destructively sampled at days 2, 4, 6, and 9 after inoculation. In both experiments the number of P. fluorescens DR54 cells decreased immediately after application as enumerated by immunostaining and microscope direct counting. Substrate-induced respiration (SIR) was taken as a measurement of the active microbial biomass, while indicators of the total microbiota (and main taxonomic groups) were obtained using the phospholipid fatty acid (PLFA) technique. In experiment 1, these parameters were unaffected by the relatively small number of BCA cells applied, whereas in experiment 2, the larger BCA input resulted in an enhanced level of both SIR and PLFAs from Gram-negative bacteria (which included the BCA itself). However, at day 9 after inoculation, treatments with P. fluorescens DR54 and controls were similar in all measured parameters in both experiments. This was also illustrated very clearly by principal component analysis of the PLFA data, which in both experiments were able to discriminate between treatments in the first days after BCA inoculation, thus confirming the sensitivity of this method. Laccase activity has a potential as an indicator of fungal stress, e.g., when challenged with an antifungal BCA. This seemed to be supported in experiment 2, where the activity of this enzyme was enhanced four-fold in the BCA treatment at day 2. Our study shows that under the present conditions, P. fluorescens DR54 disappears from the soil and causes only transient effects on the soil microbiota. It also shows that the PLFA technique is a sensitive and reliable monitoring tool in in situ assessment of BCA nontarget effect on indigenous microorganisms in soil.     

Field management of Sclerotinia stem rot of soybean using biological control agents

Biological control agents (BCAs) were evaluated for their efficacy on reducing the number of sclerotia of Sclerotinia sclerotiorum (Lib.) de Bary in the soil and on Sclerotinia stem rot in soybean production systems in Michigan. BCAs included Coniothyrium minitans CON/M/91–08 (Product name: Contans®WG), Streptomyces lydicus WYEC 108 (Actinovate®AG), Trichoderma harzianum T-22 (PlantShield®HC), and Bacillus subtilis QST 713 (Serenade®MAX). At two field locations, soil artificially infested with S. sclerotiorum sclerotia, was treated by incorporating the above BCAs in the topsoil before planting and boscalid was applied as a foliar fungicide at growth stage R1 as a positive control. C. minitans was the most effective BCA and reduced the disease severity index (DSI) by 68.5% and the number of sclerotia of S. sclerotiorum in the soil by 95.3%. S. lydicus and T. harzianum reduced DSI by 43.1% and 38.5% and sclerotia in soil by 90.6% and 70.8%, respectively. B. subtilis only had a marginal effect on S. sclerotiorum. Populations of Bacillus, Streptomyces, Trichoderma spp., and C. minitans collected from soil samples and at 3, 28, 71, and 169 days after BCA application indicated that the population of Streptomyces, Trichoderma spp., and C. minitans did not change significantly throughout the season, which may be the reason for their effectiveness.     

Effect of electrostatic spray parameters on the viability of two bacterial biocontrol agents and their deposition on blueberry flower stigmas

The fungus Monilinia vaccinii-corymbosi infects blueberry flowers via the stigma-style ovary pathway to cause mummy berry disease. Previous laboratory experiments documented considerable activity of stigma-applied biofungicides containing the bacteria Bacillus subtilis and, to a lesser extent, Pseudomonas fluorescens against flower infection by the pathogen. However, adequate and targeted delivery of the biocontrol agents to the stigmatic surfaces of open flowers in the field has remained problematic. Here we consider the application of the biofungicides Serenade AS (containing B. subtilis QST713) and BlightBan A506 (containing P. fluorescens A506) to blueberry flowers by air-assisted electrostatic spraying. In laboratory experiments with typical field-use rates, viability of B. subtilis and P. fluorescens was unaffected by different levels of induction-charging voltage (0–1.2 kV) and atomizing pressure (138–276 kPa) applied to an electrostatic spray-charging nozzle, showing that the bacteria in both formulations readily survived exposure to the intense electrical fields and near-sonic atomizing air shear encountered during electrostatic spraying. Electrostatically charged application significantly (P<0.0001) increased deposition of B. subtilis on the stigmatic surfaces of detached blueberry flower clusters by a factor of 4.5 compared with conventional hydraulic spraying; a similar comparison showed that population densities of P. fluorescens on the stigma were increased by a factor of 2.9, but this effect was not statistically significant (P=0.1487). For Serenade, the increased coverage and/or retention on the flower stigma, along with the excellent bacterial survival, portend well for electrostatic application for mummy berry disease control in the field.     

PGPR mediated management of stem blight of Phyllanthus amarus (Schum and Thonn) caused by Corynespora cassiicola (Berk and Curt) Wei

Bacillus subtilis (BSCBE4), Pseudomonas chlororaphis (PA23), endophytic P. fluorescens (ENPF1) inhibited the mycelial growth of stem blight pathogen Corynespora casiicola (Berk and Curt)Wei under in vitro. All these bacterial isolates produced both hydroxamate and carboxylate type of siderophores. But the siderophore production was maximum with the isolate ENPF1. Delivering of talc based formulation of BSCBE4 through seedling dip and foliar application effectively reduced stem blight disease incidence and increased the dry matter production under pot culture and field conditions. Application of BSCBE4, PA23 and ENPF1 increased the defense related enzymes such as peroxidase, polyphenol oxidase, chitinase and β-1,3 glucanase in P. amarus up to ten days after challenge inoculation with C. cassicola. Native gel electrophoretic analysis revealed that challenge inoculation of pathogen with BSCBE4 and PA23 induced both peroxidase and polyphnol oxidase isoforms.