Vermicompost-based bioformulation for the management of sugarbeet root rot caused by Sclerotium rolfsii

Vermicompost-based bioformulations of bacterial and fungal biocontrol agents were examined against sugarbeet root rot caused by Sclerotium rolfsii. The result showed that the Pseudomonas fluorescens strain Pf1 in combination with either Trichoderma asperellum strain TTH1 or Bacillus subtilis strain EPCO-16 performed better in reducing disease next to the chemical difenoconazole. Similarly, enhanced yield was observed in the same combination treatments under both pot and field conditions.     

Management of postharvest disease of mango anthracnose incited by Colletotrichum gleosporioides

Abstract

Among the seven fungal (Gliocladium virens, Trichoderma hamatum, T. harzianum, T. koningii, T. longibrachiatum, T. pseudokoningii and T. viride) and two bacterial (Bacillus subtilis and Pseudomonas fluorescens) antagonists screened against C. gloeosporioides under in vitro conditions, T. harzianum exhibited maximum inhibition followed by Pseudomonas fluorescens at 5 days after incubation. These fungal and bacterial antagonists were selected for application to fruits infected with pathogens. Fruits inoculated with C. gloeosporioides were dipped in spore/cell suspensions of fungal/bacterial antagonists and kept for different durations. The fungal antagonists T. harzianum and P. fluorescens were effective in checking the spread of pathogens on fruits compared with the pathogen-inoculated control.     

Bioagent based integrated management of Phytophthora blight of pigeonpea

Phytophthora blight (Phytophthora drechsleri f. sp. cajani) is one of the major yield limiting factors of short duration varieties of pigeonpea (Cajanus cajan). For eco-friendly and sustainable management of the disease, four antagonists, Pseudomonas fluorescens, Bacillus subtilis, Trichoderma viride and T. hamatum, were evaluated under in vitro and in vivo conditions. P. fluorescens produced maximum inhibition zone, while Trichoderma species overgrew on the host mycelium and caused lysis. The fungicides apron (metalaxyl), ridomil MZ (metalaxyl + mancozeb), capton (captaf), difolatan (captafol), thiram (tetramethylthiuram disulphide) and bavistin (carbendazim) at both 0.3 and 0.6% were found to be compatible with P. fluorescens while B. subtilis was compatible only with apron at 0.3%. T. viride grew and sporulated well at 0.3 and 0.6% apron and 0.2% ridomil MZ. The bioagents proved to have potential and those which were compatible under in vitro were evaluated under field conditions. The efficacy of fungicide in combination with bioagents was greater compared to fungicide alone. The integration of P. fluorescens with apron or ridomil MZ as seed treatment significantly reduced the Phytophthora blight incidence and enhanced seed germination and grain yield.     

Evaluating the promise of Trichoderma and Anabaena based biofilms as multifunctional agents in Macrophomina phaseolina-infected cotton crop

The influence of biofilmed formulations composed of Trichoderma viride and Anabaena torulosa as matrices was investigated in Macrophomina phaseolina (Tassi) Goid.-infected cotton crop, in terms of plant growth and biocontrol parameters. Trichoderma based biofilms were developed with Azotobacter chroococcum, Pseudomonas fluorescens and Bacillus subtilis, while A. torulosa biofilms were prepared using B. subtilis and T. viride as components. Scanning electron microscopy revealed significant colonisation of biofilms on the root surface, which could be correlated with lowest mortality of 5.67%, recorded using T. viride–B. subtilis biofilm. An increase of 4–7% in polyphenol oxidase enzyme activity was recorded in all biofilm-treated samples, particularly those in which B. subtilis was present. The highest value of 1360.22 µg microbial biomass carbon g^?1 soil was recorded in Anabaena–B. subtilis biofilm treatment. Significantly higher values of plant and soil nutrient parameters in treatments in which biofilms were used vis-à-vis individual cultures reveal their promise. Such novel biofilmed biofertilizers with multiple useful traits can be beneficial options for effective nutrient and pest management of cotton crop.     

Influence of phylloplane colonizing biocontrol agents on the black spot of rose caused by Diplocarpon rosae

Abstract

An attempt was made to study the biocontrol efficacy of antagonistic microorganisms in phylloplane of rose cv. Edward to manage the black spot (Diplocarpon rosae) disease. Eight antagonistic microorganisms were tested in vivo against the black spot pathogen. Among these, Trichoderma viride and Pseudomonas fluorescens pf1 reduces the mycelial growth significantly. These two biocontrol agents were evaluated for their ability to induce defense-related enzymes and chemicals in plants. Increased activity of phenylalanine ammonia lyase (PAL), peroxidase (PO), polyphenoloxidase (PPO) and total phenolics were recorded in all the biocontrol agents treated leaves. P. fluorescens Pf1 recorded early and increased synthesis of the entire defense-related enzymes and total phenol within 6 days. The application of biocontrol agents induced the defense-related enzymes involved in phenyl propanoid pathway in addition to direct antagonism, which collectively contribute for enhanced resistance against invasion of Diplocarpon rosae in rose.     

Biological control of root-rot of Coleus forskohlii Briq. using microbial inoculants

The root-rot or wilt of Coleus forskohlii is a very serious soil-borne disease caused by Fusarium chlamydosporum. A field study was undertaken to study the possibility of controlling the disease using three biocontrol agents viz., Glomus mosseae, Pseudomonas fluorescens, Trichoderma viride, singly and in combination. Planting of coleus cutting was done in wilt sick soil. Inoculation with Trichoderma viride + Glomus mosseae gave the best result in controlling the disease. The same treatment also resulted in maximum growth, yield and root forskolin concentration of coleus. Plants treated with T. viride + G. mosseae showed a disease severity index of 33.28% compared to uninoculated control plants, which had a maximum disease severity index of 85.5%. The fungicide Emisan (0.2%) was not as effective as the biocontrol agents in controlling the pathogen.     

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.     

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.     

Characterisation of antagonistic Bacillus and Pseudomonas strains for biocontrol potential and suppression of damping‐off and root rot diseases

Novel strains of rhizobacteria, Pseudomonas fluorescens Pf 9A‐14, Pseudomonas sp. Psp. 8D‐45 and Bacillus subtilis Bs 8B‐1, showed broad‐spectrum antagonistic activity and provided suppression of Pythium damping‐off and root rot of cucumber. Their biocontrol potential was further investigated for suppression of additional seedling diseases of cucumber (Phytophthora capsici) and radish (Rhizoctonia solani). Bacterial strains were also characterised for production of antibiotics, metabolites, volatiles, phytohormones and lytic enzymes. Seed and pre‐plant applications of all three antagonistic bacteria as cell suspension and talc or irradiated peat formulations to the infested potting mix provided overall high level of suppression of Phytophthora damping‐off and root rot of cucumber (66–85% healthy seedlings) and relatively low level of suppression of Rhizoctonia damping‐off of radish (18–38% healthy seedlings). Bacterial treatments also resulted in higher plant fresh masses. Seed coating with irradiated peat formulation of a mixture of three bacteria resulted in superior control of Phytophthora damping‐off and root rot of cucumber and much higher plant fresh masses. The presence of genes for biosynthesis of phenazine‐1‐carboxylic acid, 2,4‐diacetylphloroglucinol, pyrrolnitrin and pyoluteorin was confirmed in Pseudomonas strains, and that of fengycin, bacillomycin, bacilysin, surfactin and iturin A in B. subtilis Bs 8B‐1. All three strains produced HCN, salicylic acid, indole‐3‐acetic acid, protease and β‐1,3‐glucanase. Both Pseudomonas strains produced siderophores and only P. fluorescens Pf 9A‐14 showed phosphate solubilisation and chitinase activity. All three strains inhibited pathogen growth by producing volatiles, and gas chromatography–mass spectrometry analysis revealed eight compounds in Pf 9A‐14, 10 in Bs 8B‐1 and 4 in Psp 8D‐45, some with known antifungal activity. The antagonistic and plant‐growth promotion activities of these strains might be due to production of antibiotics, metabolites, lytic enzymes or phytohormones.     

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 5-fluoro-2′-deoxyuridine on bacterial growth its use for DNA labelling

Experiments on the action of 5-fluoro-2′-deoxyuridine on growth ofEscherichia coli B, CECT 101;Pseudomonas fluorescens, CECT 318;Pseudomonas savastanoi, CECT 93;Micrococcus luteus, ATCC 4698;Bacillus cereus, CIP 52.58;Bacillus macerans, ClP 52.58 andBacillus subtilis, ATCC 6633, are described. The inhibition of growth is reversed by thymine plus uracil in all cases except inPseudomonas strains in which uracil alone is active, and in which no exogenous thymine is taken up, not even in the presece of 2′-deoxyguanosine. Growth conditions for improved labelling of bacterial DNA are discussed in the light of the results.     

Multifaceted potential of bioinoculants on red bell pepper (F1 hybrid,Indam Mamatha) production

The present investigation was undertaken to determine the comparative efficacy of two arbuscular mycorrhizal (AM) fungi (Funneliformis mosseae and Acaulospora laevis) with Trichoderma viride and Pseudomonas fluorescens on growth and yield of red bell pepper. The results indicate that F. mosseae colonized the plant roots better as compared to A. laevis and promoted maximum increment in AM spore number, root colonization, leaf area, acid phosphatase activity, early fruit formation along with maximum increase in fruit nitrogen, and protein content. Whereas F. mosseae+P. fluorescens promoted maximum increase in plant height, shoot weight, mycorrhizal dependency, chlorophyll a, alkaline phosphatase activity, and fruit phosphorus content. Regarding root length, root weight, leaf photosynthesis, chlorophyll b, number of fruits per plant and their fresh weight, it was found best in F. mosseae+A. laevis+P. fluorescens. Therefore, soil inoculation with suitable bioinoculant should be used at nursery stage for better yield.     

Induction of systemic resistance by mixtures of fungal and endophytic bacterial isolates against <Emphasis Type="Italic">Pythium aphanidermatum</Emphasis>

The efficacy of eight fungal and ten endophytic bacterial isolates were tested for their ability to inhibit the growth of Pythium aphanidermatum, the causal agent of chilli damping-off. In vitro studies revealed that Trichoderma viride (TVA) and endophytic Pseudomonas fluorescens (EBL 20-PF) showed the highest inhibition of mycelial growth (71.5%; 76.7%) of P. aphanidermatum. Both the antagonists were compatible with each other and they were tested alone and together in vivo for the control of P. aphanidermatum. Besides, the induction of defense-related enzymes such as peroxidase (PO), polyphenoloxidase (PPO), phenylalanine ammonia-lyase (PAL), PR-protein like β-1, 3-glucanase and the accumulation of phenolics in chilli seedlings due to the application of bioagents were also studied. Combined application of talc-based formulation of bio-agents and challenge inoculated with P. aphanidermatum recorded maximum induction of defense-related enzymes, PR-proteins and accumulation of phenolics compared with individual application. This study suggest that the increased induction of defense-related enzymes (four to fivefold) and phenolic content (sixfold) due to the combination treatment of bioagents might have involved in the reduction of damping-off incidence and in turn increased the plant growth and yield of chilli.     

Evaluation of Some Fungi and Bacteria for Potential Control of Safflower Rust

Some fungal and bacterial isolates applied as soil and seed treatments in greenhouse trials gave a good protection against Puccinia carthami Cda. on safflower, significantly reducing the infection from rust-infested seeds. Trichoderma viride and T. harzianum added alone and in combination as air-dried inoculum to the soil were the most effective fungal isolates. However T. viride at two higher rates reduced the rate of emergence of safflower seedlings. Among bacteria, Bacillus subtilis, B. cereus, isolates of Pseudomonas fluorescens and B. thuringiensis reduced rust infection when added both as soil drench and as seed treatment. Good results in the biocontrol of P. carthami were also obtained with some combination antagonist treatments such as T. viride + B. cereus, T. viride + P. fluorescens (16), T. viride + T. harzianum + B. cereus and T. viride +, T. harzianum + P. fluorescens (16). Fungal isolates added as soil treatment increased seedling length, whereas no similar effects were observed when these isolates were applied as seed treatment.     

Biological control of rice root-knot nematode,Meloidogyne graminicola through mixture of Pseudomonas fluorescens strains

The plant growth promoting rhizobacterium, Pseudomonas fluorescens strains PF1, TDK1, and PY15 were evaluated individually and in combinations for their efficacy against root-knot nematode, Meloidogyne graminicola, in rice plants under in vitro, glass house and field conditions. Culture filtrates of these strains either individually or as mixture inhibited egg hatching and caused mortality of juveniles of M. graminicola in vitro. The efficacy was more pronounced when filtrates of the strain were used as mixtures than as individual strains. Mixtures of P. fluorescens strains signficantly reduced M. graminicola infestation when applied as bacterial suspensions through seed treatment. The higher activity of peroxidase and chitinase enzymes was observed in plants treated with P. fluorescens mixtures than the plants treated with individual strains, two strain mixtures and untreated control. In field trials on rice, talc formulations of the P. fluorescens strains individually as well as mixtures were evaluated as seed treatment, soil treatment and combination of both. A mixture of the three strains was the most effective when applied either as seed + soil treatment or as seed treatment alone. The introduced P. fluorescens strains survived endophytically on rice roots. The application of the P. fluorescens mixture PF1 + TDK1 + PY15 in seed + soil treatment resulted in higher grain yield which provided a 27.3% increase over the control followed by P. fluorescens mixture PF1 + TDK1 + PY15 in seed treatment alone, which increased the grain yield of rice by 24.7% compared to the control.     

Bacterial antagonists and hexanal-induced systemic resistance of mango fruits against Lasiodiplodia theobromae causing stem-end rot

Induction of defense-related enzymes, such as phenylalanine ammonia lyase (PAL), peroxidase (PO), polyphenol oxidase (PPO), superoxide dismutase (SOD) and catalase (CAT) due to bacterial antagonists viz., Pseudomonas fluorescens (Pf1) and Bacillus subtilis (EPCO16) and plant-derived lipoxygenase volatile compound hexanal, were studied in mango fruits against Lasiodiplodia theobromae causing stem-end rot disease. The results showed increased induction of all the defense-related enzymes in mango fruits 3–5 days after dipping treatment with combination of bacterial antagonists and hexanal when compared to untreated control treatment and treatment with fungicide carbendazim in storage condition. The increased activity was observed up to 3 days after treatment and thereafter declined. Further, increased expression of specific isoforms of PO, PPO, SOD and CAT were also observed in the treatment effect of P. fluorescens (0.5%)?+?hexanal (0.02%) treated fruits against L. theobromae. From the results obtained, it is inferred that due to the enhancement of defense-related enzymes via the phenylpropanoid pathway and due to secretion of secondary metabolites that would play significant role in hindering the pathogen quiescence and further invasion in mango fruits and thereby prevent the fruit rot.     

产褪黑素绿色木霉工程菌的构建及生理特性分析

【背景】褪黑素(melatonin)是动植物内广泛存在的一种小分子生物胺类物质,在促进生物生长和提高环境耐受性等方面发挥重要作用。木霉(Trichoderma)既是重要的生防菌株也是高效的工业产品生产菌株,能够合成丰富的代谢产物。【目的】针对目前木霉菌株中还未发现褪黑素合成的问题,构建具有褪黑素合成能力的绿色木霉(Trichoderma viride)工程菌,并对其生理特性进行研究。【方法】在绿色木霉Tv-1511中异源表达了来源于人基因组的芳烷基胺N-乙酰转移酶(aralkylamineN-acetyltransferase,AANAT)编码基因hAANAT和乙酰复合胺-O-甲基转移酶(acetylserotonin-O-methyltransferase,ASMT)编码基因hASMT,高效液相色谱法(highperformance liquid chromatography, HPLC)检测了木霉工程菌合成褪黑素的产量,并利用生化方法检测了工程菌的生长、抗逆及对植物的促生抗病能力。【结果】获得了具有褪黑素合成能力的绿色木霉工程菌,此株工程菌具有更好的生长和产孢特性、更强的逆境胁迫耐...     

Direct effect of biocontrol agents on wilt and root-rot diseases of sesame

In Egypt, sesame cultivation is subject to attack by wilt and root-rot diseases caused by Fusarium oxysporum f.sp. sesami (Zap) Cast. and Macrophomina phaseolina (Maubl) Ashby causing losses in quality and quantity of sesame seed yield. Bacillus subtilis and Trichoderma viride isolates which were isolated from sesame rhizosphere were the most effective to antagonise fungal pathogens, causing high reduction of hyphal fungal growth. Trichoderma viride was found to be mycoparasitic on Fusarium oxysporum f.sp. sesami and M. phaseolina causing morphological atternation of fungal cells and sclerotial formation. In general, Bacillus subtilis, T. viride, avirulent Fusarium oxysporum isolate and Glomus spp. (Amycorrhizae) significantly reduced wilt and root-rot incidence of sesame plants at artificially infested potted soil by each one or two pathogens. Data obtained indicate that Glomus spp significantly reduced wilt and disease severity development on sesame plants followed by T. viride. Meanwhile, avirulent Fusarium oxysporum isolate followed by Glomus spp. were effective against root-rot disease incidence caused by M. phaseolina. Glomus spp. followed by B. subtilis significantly reduced wilt and root-rot disease of sesame plants. All biotic agents significantly reduced F. oxysporum f.sp. sesami and M. phaseolina counts in sesame rhizosphere at the lowest level. Glomus spp. and the avirulent isolate of F. oxysporum eliminated M. phaseolina in sesame rhizosphere. Meanwhile T. viride was the best agent at reducing F. oxysporum at a lower level than other treatments. Application of VA mycorrhizae (Glomus spp.) in fields naturally infested by pathogens significantly reduced wilt and root-rot incidence and it significantly colonised sesame root systems and rhizospheres compared to untreated sesame transplantings.     

Pseudomonas fluorescens,a potential bacterial antagonist to control plant diseases

Abstract

Fluorescent Pseudomonads belong to plant Growth Promoting Rhizobacteria (PGPR), the important group of bacteria that play a major role in the plant growth promotion, induced systemic resistance, biological control of pathogens etc. Many strains of Pseudomonas fluorescens are known to enhance plant growth promotion and reduce severity of various diseases. The efficacy of bacterial antagonists in controlling fungal diseases was often better as alone, and sometimes in combination with fungicides. The present review refers to occurrence, distribution, mechanism, growth requirements of P. fluorescens and diseases controlled by the bacterial antagonist in different agricultural and horticultural crops were discussed. The literature in this review helps in future research programmes that aim to promote P. fluorescens as a potential bio-pesticide for augmentative biological control of many diseases of agriculture and horticultural importance.     

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.