Morphological characterization of Ampelomyces spp., a hyperparasite of Bhendi (Abelmoschus esculentus (L.) Moench) powdery mildew

Ampelomyces is a naturally occurring hyperparasite on powdery mildews. Survey was conducted in major bhendi (Abelmoschus esculentus (L.) Moench) growing districts of Tamil Nadu during June 2014 to assess the incidence of powdery mildew and to collect different isolates of Ampelomyces spp. The results of the survey revealed that the disease incidence ranged from 15.54 to 63.45 %. Ten isolates of Ampelomyces spp. were collect-ed from surveyed areas of powdery mildew. Isolation of Ampelomyces spp. was done from powdery mildew infected bhendi leaf parasitized by Ampelomyces spp. using tissue segment method. All the isolates were identified by their morphological characters. The colour of the colonies in various medium was brownish black to greenish white. Most of the isolates showed radial and fluffy growth pattern with raised growth. The pycnidia of different isolates of Ampelomyces varied in their shape and were mostly ovoid, ellipsoid, cylindrical, pyriform to globose in shape. The size of pycnidia varied from 29.2-72.5×22.4-43.1 ?m. The number of pycnidia was found to be more in isolates viz., TNAU-AQ101 and TNAU-AQ103. Pycnidiospores are hyaline, unicellular and guttulate in shape. The pycnidial production was higher in TNAU-AQ101 and TNAU-AQ103. Application of agrochemicals is one of the oldest and most effective methods to manage powdery mildew disease. However, incessant use of these agrochemicals has many demerits such as development of resistance to pathogens, residual toxicity and environmental pollution. Hence, search for an alternative means for disease management is envisaged. The genus Ampelomyces are the major antagonists as an alternative of Erysiphales fungi being a significant group of phytopathogens

Defense related enzyme induction in coconut by endophytic bacteria (EPC 5)

Endophytic bacteria Bacillus subtilis (EPC 5) was isolated and tested in vitro along with Pseudomonas fluorescens (Pf1) and the fungus Trichoderma viride (Tv1) against Ganoderma lucidum (Leys) Karst, the causal agent of basal stem rot on coconut palm. The endophytic bacterial strains namely EPC 5 and EPC 8 showed higher vigor index (germination percentage, root and shoot length) and more inhibition against G. lucidum over un-inoculated control. These strains were confirmed as Bacillus subtilis by biochemical tests, cloning and sequencing of internal transcribed spacer (ITS) region. The Bacillus subtilis (EPC 5) along with Pseudomonas fluorescens (Pf1) and Trichoderma viride (Tv1) has been tried as bioconsortia against basal stem rot disease under greenhouse conditions. The soil application of bioconsortia enriched with farm yard manure (FYM) enhanced the coconut saplings growth under greenhouse conditions and showed higher induction of defense related enzymes like peroxidase, polyphenol oxidase, phenylalanine ammonia lyase and phenols when challenged with pathogen

Chemically and biologically mediated systemic resistance in cucumber (Cucumis sativus L.) against Pseudoperonospora cubensis and Erysiphe cichoracearum

Azoxystrobin at concentrations of 0.25, 0.5 and 1.0 ml l-1, mancozeb at 2 g l-1 and Pseudomonas fl uorescens at 10 g l-1 were evaluated in cucumber for their effi cacy in inducing defense enzymes against Pseudoperonospora cubensis and Erysiphe cichoracearum. The activity of the defense enzymes peroxidase (PO), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), ß-1,3-glucanase, chitinase, catalase and defense-inducing chemicals (total phenols) increased in the azoxystrobin and P. fl uorescens treated cucumber plants. Increased expression of specifi c isoforms of PO and PPO was observed due to induced systemic resistance (ISR)

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Not AvailableThe production of one or more antibiotics is the mechanism most commonly associated with the ability of fluorescent pseudomonads to act as antagonistic agents against plant pathogenic fungi. Pseudomonas fluorescens strains were tested for antifungal activity against Pythium aphanidermatum that is known to attack turmeric crops. P. fluorescens produce antibiotics such as phenazine 1- carboxylic acid, 2, 4- diacetylphloroglucinol, pyoluteorin and pyrrolnitrin. Production of antibiotic compounds were assayed by Thin Layer Chromatography (TLC). The antifungal compounds of DAPG, phenazine and pyoluteorin were identified on TLC at Rf value of 0.88, 0.57 and 0.05 respectively. All the antibiotics extracted from different strains of P. fluorescens were tested for their antifungal activity against P. aphanidermatum. Among the strains, the antibiotics extracted from strain FP7 effectively inhibited the mycelial growth of P. aphanidermatum in agar well diffusion assayNot Availabl

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Not AvailableIn the present study, efforts were made to understand the resistant mechanism mediated by biocontrol agents in tomato plants against Helicoverpa armigera. Defense enzymes viz. peroxidase, phenylalanine ammonia-lyase, polyphenol oxidase, catalase, super oxide dismutase were analysed by Polyacrylamide Gel Electrophoresis (PAGE). SDS-PAGE was used for studying the protein profile as well as Western Blotting for chitinase. Application of a mixture of B. subtilis and B. bassiana significantly enhanced the defense-related enzymes. The results showed higher induction of PO and PPO in plants treated with combination of B2 + EPC8 than the plants treated with individual strains, chemical and untreated controls. In addition, B2 + EPC8 combination showed a greater accumulation of CAT and SOD which plays a vital role in induced resistance. Western blot analysis of chitinase revealed the induction chitinase isoform (29 KDa) in tomato plants treated with a mixture of B2 + EPC8 strains against fruit borer pest. The combined application of bioformulation also increased the accumulation of phenol as well as the defence related proteins in tomato plants. Moreover, the outcome of the present study has a potential to be used for sustainable and eco-friendly tomato production.Not Availabl

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Not AvailableThe genetic diversity of Beauveria bassiana isolated from the different ecosystem of Tamil Nadu was analyzed. Totally fifteen isolates were used in this study. The genetic variability and relationship among 15 isolates were analyzed using 15 Random Amplified Polymorphic DNA (RAPD) markers. Among 15 primers used, six primers viz., OPA02, OPF01, OPX07, OPA03, OPZ19 and OPG19 showed 100 percent polymorphism. The relationships among the isolates were examined and represented as dendrogram by using UPGMA clusters. Results revealed that similarity coefficients of B. bassiana isolates based on RAPD markers ranged from 42.00 to 86.00 percent. The maximum of 85 percent similarity was observed between the isolates B23 and B24. All isolates have significantly different from one another. Overall we concluded that RAPD was found to be better in assessing genetic diversity among B. bassiana isolates.Not Availabl

Potential of a rhizobacterium Bacillus subtilis (Bbv 57) on Fusarium oxysporum f. sp. gerberae and Meloidogyne incognita infecting Gerbera grown in protected cultivation.

Not AvailableNinety five bacterial strains were isolated from the rhizosphere and soils of flower crops, specifically gerbera, carnation and tuberose, were preliminarily screened against Fusarium oxysporum f. sp. gerberae in vitro along with five elite strains Bbv 57, EPCO 16, EPC 5, EPC 8 and Pf 1 obtained from Department of Plant Pathology, TNAU, Coimbatore, India. The results revealed that the strain Bbv 57 had highest inhibition of 50.00% and showed the maximum value for the assays that is siderophore, hydrogen cyanide, IAA, GA3 and salicylic acid production (3.68 O.D. value; 14.05 μgml-1; 44.40 μg ml-1; 25.28 μg ml-1 and 19.25 μg ml-1 respectively). It also showed resistance to antibiotics namely ampicillin, erythromycin, clindamycin. The highest exopolysaccharides, biofilm production was observed and had lowest protease production clearly indicated that it is non - pathogenic to plants. Further, the polymerase chain reaction using16S rRNA intervening sequencing showed 100% homology to Bacillus subtilis (KF718836) and showed positive for quorum sensing regulator genes of aiiA and comQ. Additionally, the culture filtrate assay also produced significant reduction in egg hatching capacity and juvenile mortality of root-knot nematode Meloidogyne incognita. Further, the HPLC study showed 91.69 μg μl-1 of surfactin with the retention time of 2.304 min and 0.453 μg μl-1 of Iturin with the retention time of 8.739 min at 205 nm. Whereas, GCMS analysis has detected the aliphatic hydrocarbons responsible for antifungal, antibacterial and nematicidal activity.Not Availabl

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Not AvailableThe genetic diversity of fluorescent pseudomonads associated with the turmeric (Curcuma longa L.) rhizosphere of Tamil Nadu, India was analyzed. Selected isolates were identified by ITS sequence analysis. Based on 16S rRNA sequence similarity, the isolates were identified as Pseudomonas fluorescens, P. stutzeri and Pseudomonas sp. The genetic variability and relationship among 15 fluorescent pseudomonads were analysed using 15 Random Amplified Polymorphic DNA (RAPD) and 13 Inter-Simple Sequence Repeat (ISSR) markers. Results revealed that ISSR markers were more efficient than the RAPD assay with regards to polymorphism detection. Also, total amplicons, the average number of polymorphic loci per primer, average polymorphic information content (PIC), marker index (MI) values and effective multiplex ratio (EMR) were more for ISSR than for RAPD. The similarity coefficients of fluorescent pseudomonads based on RAPD and ISSR markers ranged from 50.00 to 75.00 and 49.00 to 85.00 per cent respectively. Overall, we concluded that ISSR was found to be better than RAPD in assessing genetic diversity among fluorescent pseudomonads.Not Availabl

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Not AvailableTurmeric rhizome rot is a devastating disease posting the major threat to turmeric cultivation. Plant growthpromoting rhizobacteria (PGPR) Pseudomonas fluorescens strain FP7 was found to exhibit disease reduction and plant growth promotional activity in various crop plants in our previous studies. In this study, efforts were made to evaluate the efficacy of P. fluorescens (FP7) bioformulations against rhizome rot disease in turmeric plants. Among the FP7 bioformulations tested, a combination of rhizome dip and soil drench of FP7 liquid formulation recorded the minimum disease incidence under glasshouse (19.00%) and field conditions (10.18% and 13.29% in the trial I and trial II respectively). Furthermore, the 2D-PAGE analysis was performed to elucidate the molecular responses of tripartite interaction between host-pathogen-bioagent through protein profiling. A total of 12 differentially expressed proteins were identified and mass spectrometry (MS) analysis revealed that proteins such as tryptophan synthase beta subunit-like, phosphoglycerate kinase, cellulose synthase 6 isoform, ATP synthase subunit beta, cysteine-rich peptide, ribosomal protein S3, clathrin assembly protein and disease resistance protein RPP13-like were found to be differentially regulated. The differentially expressed proteins during tripartite interaction might be directly or indirectly involved in disease resistance in turmeric plants. This study provides an initial insight into the molecular mechanism of tripartite interaction between host-pathogen - bioagent in turmeric plantsNot Availabl

Biocontrol of wilt-nematode complex infecting gerbera by Bacillus subtilis under protected cultivation

Abstract A strong antibiotic producer, Bacillus subtilis strain Bbv 57 (KF718836), has been utilized for the management of wilt-nematode complex (Fusarium oxysporum f. sp. gerberae, Meloidogyne incognita) in gerbera under greenhouse conditions in the Department of Floriculture, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India. The strain strongly inhibited F. oxysporum f. sp. gerberae (KM523669) mycelial growth to an extent of 44.33 and 63.33%, at 10 and 100 μl, of culture filtrate, respectively. Further, the culture filtrate at 100% concentration exerted lethal effect on nematode eggs (7.00 hatched) and juveniles (87% mortality) compared to control. The analysis of TLC revealed that Bbv 57 showed the cyclic antimicrobial peptides surfactin and iturin that were confirmed by PCR. Strain Bbv 57 was able to produce antifungal and anti-nematicidal activity with reduced wilt incidence (15.33%) and thus holds a great potential for use in the biocontrol of Fusarium wilt-root-knot nematode disease complex in gerbera under greenhouse conditions