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1.
Electron. j. biotechnol ; 47: 43-50, sept. 2020. tab, graf
Article in English | LILACS | ID: biblio-1253024

ABSTRACT

BACKGROUND: Rice sheath blight (caused by Rhizoctonia solani) and tobacco mosaic virus are very important plant diseases, causing a huge loss in global crop production. Paenibacillus kribbensis PS04 is a broad-spectrum biocontrol agent, used for controlling these diseases. Previously, extracellular polysaccharides (EPS) from P. kribbensis PS04 had been purified and their structure was inferred to be fructosan. This study aimed to evaluate the effects of exogenous EPS treatment on plant­pathogen interactions. RESULTS: Plant defense genes such as phenylalanine ammonia-lyase, catalase, chitinase, allene oxide synthase, and PR1a proteins were significantly induced by exogenous EPS treatment. Moreover, subsequent challenge of EPSpretreated plants with the pathogens (R. solani or tobacco mosaic virus) resulted in higher expression of defenseassociated genes. Increased activities of defense-associated enzymes, total phenols, and flavonoids were also observed in EPS pretreated plants. The contents of malondialdehyde in plants, which act as indicator of lipid peroxidation, were reduced by EPS treatment. CONCLUSIONS: This study comprehensively showed that EPS produced from P. kribbensis PS04 enhances disease resistance in plants by the activation of defense-associated genes as well as through the enhancement of activities of defense-related enzymes.


Subject(s)
Plant Diseases/immunology , Rhizoctonia/pathogenicity , Tobacco Mosaic Virus/pathogenicity , Paenibacillus/immunology , Plant Diseases/microbiology , Polysaccharides, Bacterial , Pest Control, Biological , Host-Pathogen Interactions , Paenibacillus/genetics , Disease Resistance/genetics , Real-Time Polymerase Chain Reaction , Fructose/analogs & derivatives
2.
Electron. j. biotechnol ; 44: 14-18, Mar. 2020. ilus, graf
Article in English | LILACS | ID: biblio-1087629

ABSTRACT

BACKGROUND: Although bioactive metabolites capable of causing oxidative photo-necrosis in plant tissues have been identified in fungi, little is known about this type of mechanism in bacteria. These metabolites act as photosensitizers that generate reactive oxygen species (ROS) capable of causing damage to cells. In addition, these metabolites can pass into an energetically excited state when they receive some luminous stimulus, a condition in which they interact with other molecules present in the environment, such as molecular oxygen (O2), also known as triplet oxygen (3 O2), generating ROS. RESULTS: The suspension of the bacterial culture of Pseudomonas cedrina was shown to produce foliar necrosis in papaya leaves (Carica papaya L.) only in the presence of sunlight, which is evidence of photosensitizing mechanisms that generate singlet oxygen (1 O2). From the chemical study of extracts obtained from this bacteria, 3-(4-(2-carboxipropyl) phenyl) but-2-enoic acid (1) was isolated. This compound, in the presence of light and triplet oxygen (3 O2), was able to oxidize ergosterol to its peroxide, since it acted as a photosensitizer producing 1 O2, with which it was corroborated that a photosensitization reaction occurs, mechanism by which this bacterium could prove to cause oxidative foliar photo-necrosis. CONCLUSIONS: P. cedrina was able to induce oxidative foliar photo-necrosis because of its potential ability to produce photosensitizing metabolites that generate singlet oxygen in the plants it colonizes. Based on the above, it can be proposed that some bacteria can cause oxidative foliar photo-necrosis as an important mechanism in the pathogenesis of host species.


Subject(s)
Plant Diseases/microbiology , Pseudomonas/physiology , Carica/microbiology , Singlet Oxygen/metabolism , Pseudomonas/metabolism , Acids , Reactive Oxygen Species , Plant Leaves/microbiology , Photooxidation , Light , Necrosis
3.
Arq. Inst. Biol ; 87: e0832019, 2020. ilus, graf
Article in English | ID: biblio-1130144

ABSTRACT

This study aimed to develop and validate a standard area diagram (SAD) set to estimate the severity of bacterial blight of eucalyptus caused by Erwinia psidii. For this purpose, an eight-level SAD was developed and validated by ten inexperienced raters. Accuracy and precision of the estimates by each rater, with and without the SAD, were determined based on Lin's concordance correlation coefficient. The proposed SAD improved the accuracy and precision of the estimates. The SAD set studied here is a useful tool in assessments of bacterial blight of eucalyptus for epidemiological research and breeding programs.(AU)


Este trabalho objetivou o desenvolvimento de uma escala para estimar a severidade da seca-de-ponteiros do eucalipto causada por Erwinia psidii. Para isso, uma escala de oito níveis foi desenvolvida e validada por dez avaliadores inexperientes. A acurácia e precisão das estimativas de cada avaliador, com e sem a escala, foram determinadas baseadas no coeficiente de correlação concordante de Lin. A escala proposta melhorou a acurácia e a precisão das estimativas. A escala estudada se mostrou uma ferramenta útil na avaliação da seca-de-ponteiros do eucalipto para estudos epidemiológicos e em programas de melhoramento.(AU)


Subject(s)
Plant Diseases/microbiology , Bacterial Infections/classification , Erwinia , Eucalyptus/microbiology , Reproducibility of Results
4.
Braz. arch. biol. technol ; 62: e19170610, 2019. tab
Article in English | LILACS | ID: biblio-1039135

ABSTRACT

Abstract The white mold, caused by Sclerotinia sclerotiorum (Lib.) de Bary, is one of the most important diseases of soybean. The objective of the present work was to evaluate the soybean reaction to the fungus S. sclerotiorum, which causes white mold, in a partial diallel with 50 crosses. The Group I of parents was composed of ten experimental lines with high grain yield and the group II consisted in five genotypes with possible resistance to white mold. Ten plants of each cross in the F4 generation and the parents were evaluated for reaction to fungus infection using the method of inoculation in detached leaves in order to assess the severity of the disease and to later estimate the combining abilities. Estimates of the specific combining ability (SCA) was a significant reaction to S. sclerotiorum, indicating that there is variability for fungus resistance due to non-additive genes action.


Subject(s)
Plant Diseases/microbiology , Ascomycota , Soybeans/microbiology , Agricultural Inoculants
5.
Braz. j. microbiol ; 49(4): 840-847, Oct.-Dec. 2018. graf
Article in English | LILACS | ID: biblio-974284

ABSTRACT

ABSTRACT Anthracnose is a crop disease usually caused by fungi in the genus Colletotrichum or Gloeosporium. These are considered one of the main pathogens, causing significant economic losses, such as in peppers and guarana. The current forms of control include the use of resistant cultivars, sanitary pruning and fungicides. However, even with the use of some methods of controlling these cultures, the crops are not free of anthracnose. Additionally, excessive application of fungicides increases the resistance of pathogens to agrochemicals and cause harm to human health and the environment. In order to find natural antifungal agents against guarana anthracnose, endophytic fungi were isolated from Amazon guarana. The compounds piliformic acid and cytochalasin D were isolated by chromatographic techniques from two Xylaria spp., guided by assays with Colletotrichum gloeosporioides. The isolated compounds were identified by spectrometric techniques, as NMR and mass spectrometry. This is the first report that piliformic acid and cytochalasin D have antifungal activity against C. gloeosporioides with MIC 2.92 and 2.46 µmol mL-1 respectively. Captan and difenoconazole were included as positive controls (MIC 16.63 and 0.02 µmol mL-1, respectively). Thus, Xylaria species presented a biotechnological potential and production of different active compounds which might be promising against anthracnose disease.


Subject(s)
Plant Diseases/prevention & control , Xylariales/chemistry , Paullinia/microbiology , Endophytes/chemistry , Fungicides, Industrial/pharmacology , Phylogeny , Plant Diseases/microbiology , Mass Spectrometry , Xylariales/isolation & purification , Xylariales/genetics , Xylariales/metabolism , Molecular Structure , Colletotrichum/drug effects , Colletotrichum/physiology , Endophytes/isolation & purification , Endophytes/genetics , Endophytes/metabolism , Fungicides, Industrial/isolation & purification , Fungicides, Industrial/chemistry
6.
Braz. j. microbiol ; 49(supl.1): 246-259, 2018. tab, graf
Article in English | LILACS | ID: biblio-974333

ABSTRACT

ABSTRACT Bacterial spot is an important disease of pepper in Bulgaria and Macedonia. For characterization of Xanthomonas species associated with bacterial spot, 161 strains were collected from various field pepper-growing regions. Among them, 131 strains were identified as Xanthomonas euvesicatoria and 30 as Xanthomonas vesicatoria using species-specific primers and polymerase chain reaction followed by restriction fragment length polymorphism analysis. To assess the genetic diversity of the strains, two methods (Random Amplified Polymorphic DNA and Repetitive Element Palindromic-Polymerase Chain Reaction) were applied. Discriminatory index was calculated and analysis of molecular variance was carried out.Combined random amplified polymorphic DNA analysis of the X. euvesicatoria strains with primers CUGEA-4 and CUGEA-6 had greater discriminative power (0.60) than repetitive element palindromic-polymerase chain reaction with ERIC and BOX A1R primers, which makes this method applicable for strain diversity evaluation. Discrimination among the X. vesicatoria strains was achieved by the use of ERIC primers and only for the Bulgarian strains. The results demonstrated that X. euvesicatoria was more diverse than X. vesicatoria and heterogeneity was observed mainly in the Bulgarian populations. According to the analysis of molecular variance, genetic variations in X. euvesicatoria were observed among and within populations from different regions, while the differences between the two countries were minor. Following the principal coordinates analysis, a relation between the climatic conditions of the regions and a genetic distance of the populations may be suggested.


Subject(s)
Plant Diseases/microbiology , Xanthomonas/isolation & purification , Xanthomonas/genetics , Capsicum/microbiology , Phylogeny , Genetic Variation , Xanthomonas/classification , Xanthomonas/physiology , Bulgaria , Polymerase Chain Reaction , DNA Primers/genetics , Greece
7.
Braz. j. microbiol ; 49(supl.1): 269-275, 2018. tab, graf
Article in English | LILACS | ID: biblio-974344

ABSTRACT

ABSTRACT Fusarium oxysporum f. sp. lycopersici is a phytopathogenic fungus that causes vascular wilt in tomato plants. In this work we analyze the influence of metal salts such as iron and copper sulphate, as well as that of bathophenanthrolinedisulfonic acid (iron chelator) and bathocuproinedisulfonic acid (copper chelator) on the activity of laccases in the intra (IF) and extracellular fractions (EF) of the wild-type and the non-pathogenic mutant strain (rho1::hyg) of F. oxysporum. The results show that laccase activity in the IF fraction of the wild and mutant strain increased with the addition of iron chelator (53.4 and 114.32%; respectively). With copper, it is observed that there is an inhibition of the activity with the addition of CuSO4 for the EF of the wild and mutant strain (reduction of 82 and 62.6%; respectively) and for the IF of the mutant strain (54.8%). With the copper chelator a less laccase activity in the IF of the mutant strain was observed (reduction of 53.9%). The results obtained suggest a different regulation of intracellular laccases in the mutant strain compared with the wild type in presence of CuSO4 and copper chelator which may be due to the mutation in the rho gene.


Subject(s)
Fungal Proteins/metabolism , Copper/metabolism , Laccase/metabolism , Fusarium/enzymology , Iron/metabolism , Plant Diseases/microbiology , Fungal Proteins/genetics , Fungal Proteins/chemistry , Lycopersicon esculentum/microbiology , Laccase/genetics , Laccase/chemistry , Fusarium/genetics , Fusarium/chemistry
8.
Braz. j. microbiol ; 49(supl.1): 236-245, 2018. graf
Article in English | LILACS | ID: biblio-974331

ABSTRACT

ABSTRACT Salinity and alkalinity are major abiotic stresses that limit growth and development of poplar. We investigated biocontrol potential of saline- and alkaline-tolerant mutants of Trichoderma asperellum to mediate the effects of salinity or alkalinity stresses on Populus davidiana × P. alba var. pyramidalis (PdPap poplar) seedlings. A T-DNA insertion mutant library of T. asperellum was constructed using an Agrobacterium tumefaciens mediated transformation system; this process yielded sixty five positive transformants (T1-T65). The salinity tolerant mutant, T59, grew in Potato Dextrose Agar (PDA) containing up to 10% (1709.40 mM) NaCl. Under NaCl-rich conditions, T59 was most effective in inhibiting Alternaria alternata (52.00%). The alkalinity tolerant mutants, T3 and T5, grew in PDA containing up to 0.4% (47.62 mM) NaHCO3. The ability of the T3 and T5 mutants to inhibit Fusarium oxysporum declined as NaHCO3 concentrations increased. NaHCO3 tolerance of the PdPap seedlings improved following treatment with the spores of the WT, T3, and T5 strains. The salinity tolerant mutant (T59) and two alkalinity tolerant mutants (T3 and T5) generated in this study can be applied to decrease the incidence of pathogenic fungi infection under saline or alkaline stress.


Subject(s)
Plant Diseases/microbiology , Trichoderma/physiology , Sodium Chloride/metabolism , Populus/growth & development , Alkalies/metabolism , Alternaria/physiology , Antibiosis , Plant Diseases/prevention & control , Stress, Physiological , Trichoderma/genetics , Populus/microbiology , Seedlings/growth & development , Seedlings/microbiology
9.
Braz. j. microbiol ; 48(4): 706-714, Oct.-Dec. 2017. tab, graf
Article in English | LILACS | ID: biblio-889164

ABSTRACT

ABSTRACT Tomato is one of the most important vegetables in the world. Decay after harvest is a major issue in the development of tomato industry. Currently, the most effective method for controlling decay after harvest is storage of tomato at low temperature combined with usage of chemical bactericide; however, long-term usage of chemical bactericide not only causes pathogen resistance but also is harmful for human health and environment. Biocontrol method for the management of disease after tomato harvest has great practical significance. In this study, antagonistic bacterium B-6-1 strain was isolated from the surface of tomato and identified as Enterobacter cowanii based on morphological characteristics and physiological and biochemical features combined with sequence analysis of 16SrDNA and ropB gene and construction of dendrogram. Effects of different concentrations of antagonistic bacterium E. cowanii suspension on antifungal activity after tomato harvest were analyzed by mycelium growth rate method. Results revealed that antifungal activity was also enhanced with increasing concentrations of antagonistic bacterium; inhibitory rates of 1 × 105 colony-forming units (cfu)/mL antagonistic bacterial solution on Fusarium verticillioides, Alternaria tenuissima, and Botrytis cinerea were 46.31%, 67.48%, and 75.67%, respectively. By using in vivo inoculation method, it was further confirmed that antagonistic bacterium could effectively inhibit the occurrence of B. cinerae after tomato harvest, biocontrol effect of 1 × 109 cfu/mL zymotic fluid reached up to 95.24%, and antagonistic bacterium E. cowanii has biocontrol potential against B. cinerea after harvest of fruits and vegetables.


Subject(s)
Plant Diseases/microbiology , Lycopersicon esculentum/microbiology , Enterobacter/isolation & purification , Enterobacter/physiology , Antibiosis , Plant Diseases/prevention & control , Botrytis/growth & development , Botrytis/physiology , Enterobacter/classification , Enterobacter/genetics , Alternaria/growth & development , Alternaria/physiology , Fruit/microbiology , Fusarium/growth & development , Fusarium/physiology
10.
Braz. j. microbiol ; 48(2): 193-195, April.-June 2017. tab
Article in English | LILACS | ID: biblio-839391

ABSTRACT

Abstract Ralstonia solanacearum is a heterogeneous species complex causing bacterial wilts in more than 450 plant species distributed in 54 families. The complexity of the genome and the wide diversity existing within the species has led to the concept of R. solanacearum species complex (RsSC). Here we report the genome sequence of the four strains (RS2, RS25, RS48 and RS75) belonging to three of the four phylotypes of R. solanacearum that cause potato bacterial wilt in India. The genome sequence data would be a valuable resource for the evolutionary, epidemiological studies and quarantine of this phytopathogen.


Subject(s)
Plant Diseases/microbiology , Solanum tuberosum/microbiology , DNA, Bacterial/chemistry , Genome, Bacterial , Sequence Analysis, DNA , Ralstonia solanacearum/genetics , Genotype , DNA, Bacterial/genetics , Ralstonia solanacearum/isolation & purification , Ralstonia solanacearum/classification , India
11.
Braz. j. microbiol ; 48(1): 62-70, Jan.-Mar. 2017. tab, graf
Article in English | LILACS | ID: biblio-839357

ABSTRACT

Abstract This study aimed to evaluate the biocontrol potential of bacteria isolated from different plant species and soils. The production of compounds related to phytopathogen biocontrol and/or promotion of plant growth in bacterial isolates was evaluated by measuring the production of antimicrobial compounds (ammonia and antibiosis) and hydrolytic enzymes (amylases, lipases, proteases, and chitinases) and phosphate solubilization. Of the 1219 bacterial isolates, 92% produced one or more of the eight compounds evaluated, but only 1% of the isolates produced all the compounds. Proteolytic activity was most frequently observed among the bacterial isolates. Among the compounds which often determine the success of biocontrol, 43% produced compounds which inhibit mycelial growth of Monilinia fructicola, but only 11% hydrolyzed chitin. Bacteria from different plant species (rhizosphere or phylloplane) exhibited differences in the ability to produce the compounds evaluated. Most bacterial isolates with biocontrol potential were isolated from rhizospheric soil. The most efficient bacteria (producing at least five compounds related to phytopathogen biocontrol and/or plant growth), 86 in total, were evaluated for their biocontrol potential by observing their ability to kill juvenile Mesocriconema xenoplax. Thus, we clearly observed that bacteria that produced more compounds related to phytopathogen biocontrol and/or plant growth had a higher efficacy for nematode biocontrol, which validated the selection strategy used.


Subject(s)
Plant Diseases/microbiology , Soil Microbiology , Bacteria/classification , Bacterial Physiological Phenomena , Bacteria/isolation & purification , Bacteria/genetics , RNA, Ribosomal, 16S , Enzymes/biosynthesis , Rhizosphere , Ammonia/metabolism , Hydrolysis , Antibiosis
12.
Braz. j. microbiol ; 47(4): 1020-1029, Oct.-Dec. 2016. tab
Article in English | LILACS | ID: biblio-828195

ABSTRACT

Abstract Sweet or bell pepper is a member of the Solanaceae family and is regarded as one of the most popular and nutritious vegetable. Blight, in the form of leaf and fruit blight, has been observed to infect bell pepper crops cultivated at the horticulture farm in Rajasthan College of Agriculture, Udaipur, India. Based on disease severity, we attempted to curb this newly emerged problem using different fungicides, plant extracts, bio-control agents, and commercial botanicals against the fungus in laboratory and pot experiments. Bio-control agent Trichoderma viride and plant growth promoting Rhizobacteria (PGPR) isolate Neist-2 were found to be quite effective against bell pepper blight. All evaluated fungicides, botanicals, commercial botanicals, and bio-control agents in vitro were further studied as seed dressers and two foliar sprays at ten days interval in pot experiments. The combinations of Vitavax, PGPR isolate Neist-2, and Mehandi extract were found to be very effective against bell pepper blight followed by Vitavax, T. viride, and Mehandi extract used individually. All treatments in the pot experiments were found to significantly reduce seedling mortality and enhance plant biomass of bell pepper. Thus, these experimental findings suggest that a better integrated management of bell pepper blight could be achieved by conducting field trials in major bell pepper- and chilli-cultivated areas of the state. Besides fungicides, different botanicals and commercial botanicals also seem to be promising treatment options. Therefore, the outcome of the present study provides an alternate option of fungicide use in minimizing loss caused by Drechslera bicolor.


Subject(s)
Plant Diseases/microbiology , Ascomycota , Capsicum/microbiology , Ascomycota/drug effects , Capsicum/chemistry , Plant Extracts/pharmacology , Plant Extracts/chemistry , Microbial Sensitivity Tests , Seedlings/drug effects , Antifungal Agents/pharmacology , Antifungal Agents/chemistry
13.
Braz. j. microbiol ; 47(4): 793-799, Oct.-Dec. 2016. tab
Article in English | LILACS | ID: biblio-828190

ABSTRACT

Abstract Triazole fungicides are used broadly for the control of infectious diseases of both humans and plants. The surge in resistance to triazoles among pathogenic populations is an emergent issue both in agriculture and medicine. The non-rational use of fungicides with site-specific modes of action, such as the triazoles, may increase the risk of antifungal resistance development. In the medical field, the surge of resistant fungal isolates has been related to the intensive and recurrent therapeutic use of a limited number of triazoles for the treatment and prophylaxis of many mycoses. Similarities in the mode of action of triazole fungicides used in these two fields may lead to cross-resistance, thus expanding the spectrum of resistance to multiple fungicides and contributing to the perpetuation of resistant strains in the environment. The emergence of fungicide-resistant isolates of human pathogens has been related to the exposure to fungicides used in agroecosystems. Examples include species of cosmopolitan occurrence, such as Fusarium and Aspergillus, which cause diseases in both plants and humans. This review summarizes the information about the most important triazole fungicides that are largely used in human clinical therapy and agriculture. We aim to discuss the issues related to fungicide resistance and the recommended strategies for preventing the emergence of triazole-resistant fungal populations capable of spreading across environments.


Subject(s)
Humans , Triazoles/poisoning , Ecosystem , Drug Resistance, Fungal , Agriculture , Fungi/drug effects , Antifungal Agents/pharmacology , Plant Diseases/microbiology , Triazoles/therapeutic use , Fungi/physiology , Fungicides, Industrial , Mycoses/microbiology , Mycoses/drug therapy , Antifungal Agents/therapeutic use
14.
Braz. j. microbiol ; 47(4): 1014-1019, Oct.-Dec. 2016. tab, graf
Article in English | LILACS | ID: biblio-828192

ABSTRACT

Abstract Apple is one of the most important temperate fruit to Brazil economy, and the use of synthetic chemicals has been the main method for reducing postharvest diseases, such as the blue mold, caused by Penicillium expansum. This work intends to evaluate the practical utilization of chitosan for blue mold control. For this purpose, fruits were treated in a preventive and curative way, immersing the fruits in chitosan solution (5 or 10 mg mL-1), or adding a single drop of this solution (10 mg mL-1) directly into the injuries. The eradicative effect of the polysaccharide was also evaluated in vitro and in vivo. Chitosan did not show a curative effect against the blue mold, and its eradicative effect was only evidenced on the higher concentration (10 mg mL-1). On the other hand, preventively, without the addition of adjuvants, chitosan reduced blue mold incidence in fruits by 24% and 93%, through the immersion or the single drop methods, respectively. Thus, it was found that, for long scale utilization, some improvements in the physico-chemical properties of the chitosan are needed, since it was only capable to prevent the infection by P. expansum when directly added on the fruit injury.


Subject(s)
Penicillium/drug effects , Plant Diseases/microbiology , Plant Diseases/therapy , Malus/microbiology , Chitosan/pharmacology , Antifungal Agents/pharmacology , Plant Diseases/prevention & control , Time Factors , Chitosan/chemistry , Fruit/microbiology , Antifungal Agents/chemistry
16.
Braz. j. microbiol ; 47(3): 529-530, July-Sept. 2016. tab
Article in English | LILACS | ID: lil-788969

ABSTRACT

ABSTRACT Pseudomonas syringae pv. actinidifoliorum causes necrotic spots on the leaves of Actinidia deliciosa and Actinidia chinensis. P. syringae pv. actinidifoliorum has been detected in New Zealand, Australia, France and Spain. Four lineages were previously identified within the P. syringae pv. actinidifoliorum species group. Here, we report the draft genome sequences of five strains of P. syringae pv. actinidifoliorum representative of lineages 1, 2 and 4, isolated in France. The whole genomes of strains isolated in New Zealand, representative of P. syringae pv. actinidifoliorum lineages 1 and 3, were previously sequenced. The availability of supplementary P. syringae pv. actinidifoliorum genome sequences will be useful for developing molecular tools for pathogen detection and for performing comparative genomic analyses to study the relationship between P. syringae pv. actinidifoliorum and other kiwifruit pathogens, such as P. syringae pv. actinidiae.


Subject(s)
Genome, Viral , Sequence Analysis, DNA , Pseudomonas syringae/classification , Pseudomonas syringae/genetics , Plant Diseases/microbiology , Genomics/methods , Pseudomonas syringae/isolation & purification , High-Throughput Nucleotide Sequencing
17.
Braz. j. microbiol ; 47(2): 468-479, Apr.-June 2016. tab, graf
Article in English | LILACS | ID: lil-780832

ABSTRACT

Abstract Metabolites of mycoparasitic fungal species such as Trichoderma harzianum 88 have important biological roles. In this study, two new ketoacyl synthase (KS) fragments were isolated from cultured Trichoderma harzianum 88 mycelia using degenerate primers and analysed using a phylogenetic tree. The gene fragments were determined to be present as single copies in Trichoderma harzianum 88 through southern blot analysis using digoxigenin-labelled KS gene fragments as probes. The complete sequence analysis in formation of pksT-1 (5669 bp) and pksT-2 (7901 bp) suggests that pksT-1 exhibited features of a non-reducing type I fungal PKS, whereas pksT-2 exhibited features of a highly reducing type I fungal PKS. Reverse transcription polymerase chain reaction indicated that the isolated genes are differentially regulated in Trichoderma harzianum 88 during challenge with three fungal plant pathogens, which suggests that they participate in the response of Trichoderma harzianum 88 to fungal plant pathogens. Furthermore, disruption of the pksT-2 encoding ketosynthase–acyltransferase domains through Agrobacterium -mediated gene transformation indicated that pksT-2 is a key factor for conidial pigmentation in Trichoderma harzianum 88.


Subject(s)
Trichoderma/enzymology , Fungal Proteins/metabolism , Polyketide Synthases/metabolism , Plant Diseases/microbiology , Trichoderma/classification , Trichoderma/genetics , Fungal Proteins/genetics , Fungal Proteins/chemistry , Molecular Sequence Data , Gene Expression Regulation, Fungal , Sequence Alignment , Amino Acid Sequence , Mycelium/enzymology , Mycelium/genetics , Polyketide Synthases/genetics , Polyketide Synthases/chemistry
18.
Braz. j. microbiol ; 47(2): 518-526, Apr.-June 2016. graf
Article in English | LILACS | ID: lil-780835

ABSTRACT

Abstract Citrus canker, caused by the Gram-negative bacterium Xanthomonas citri subsp. citri (Xac), is one of the most devastating diseases to affect citrus crops. There is no treatment for citrus canker; effective control against the spread of Xac is usually achieved by the elimination of affected plants along with that of asymptomatic neighbors. An in depth understanding of the pathogen is the keystone for understanding of the disease; to this effect we are committed to the development of strategies to ease the study of Xac. Genome sequencing and annotation of Xac revealed that ∼37% of the genome is composed of hypothetical ORFs. To start a systematic characterization of novel factors encoded by Xac, we constructed integrative-vectors for protein expression specific to this bacterium. The vectors allow for the production of TAP-tagged proteins in Xac under the regulation of the xylose promoter. In this study, we show that a TAP-expression vector, integrated into the amy locus of Xac, does not compromise its virulence. Furthermore, our results also demonstrate that the polypeptide TAP can be overproduced in Xac and purified from the soluble phase of cell extracts. Our results substantiate the use of our vectors for protein expression in Xac thus contributing a novel tool for the characterization of proteins and protein complexes generated by this bacterium in vivo.


Subject(s)
Bacterial Proteins/genetics , Xanthomonas/genetics , Recombinant Fusion Proteins/genetics , Plant Diseases/microbiology , Bacterial Proteins/isolation & purification , Bacterial Proteins/metabolism , Xanthomonas/metabolism , Xanthomonas/chemistry , Recombinant Fusion Proteins/isolation & purification , Recombinant Fusion Proteins/metabolism , Open Reading Frames , Citrus/microbiology , Genetic Vectors/genetics , Genetic Vectors/metabolism
19.
Braz. j. microbiol ; 47(1): 10-17, Jan.-Mar. 2016. graf
Article in English | LILACS | ID: lil-775109

ABSTRACT

Abstract The antagonistic potential of Trichoderma strains was assayed by studying the effect of their culture filtrate on the radial growth of Sclerotium rolfsii, the causal agent of chickpea collar rot. Trichoderma harzianum-1432 (42.2%) and Trichoderma atroviride (40.3%) were found to be strong antagonists. To enhance their antagonistic potential, mutagenesis of these two selected strains was performed. Two mutants, Th-m1 and T. atroviride m1, were found to be more effective than their parent strains. The enzymatic activities of the selected parent and mutant strains were assayed, and although both mutants were found to have enhanced enzymatic activities compared to their respective parent strains, Th-m1 possessed the maximum cellulase (5.69 U/mL) and β-1,3-glucanase activity (61.9 U/mL). Th-m1 also showed high competitive saprophytic ability (CSA) among all of the selected parent and mutant strains, and during field experiments, Th-m1 was found to successfully possess enhanced disease control (82.9%).


Subject(s)
Antibiosis/drug effects , Basidiomycota/growth & development , Mutagenesis , Mutagens/metabolism , Plant Diseases/prevention & control , Trichoderma/drug effects , Trichoderma/physiology , Cicer/microbiology , Hydrolases/analysis , Mutation , Plant Diseases/microbiology , Trichoderma/enzymology , Trichoderma/growth & development
20.
Braz. j. microbiol ; 46(4): 1093-1101, Oct.-Dec. 2015. graf
Article in English | LILACS | ID: lil-769640

ABSTRACT

Abstract Sampling of agricultural soils from the Mexican northeastern region was performed to detect Trichoderma spp., genetically characterize it, and assess its potential use as a biologic control agent against Macrophomina phaseolina. M. phaseolina is a phytopathogen that attacks over 500 species of cultivated plants and causes heavy losses in the regional sorghum crop. Sampling was performed immediately after sorghum or corn harvest in an area that was approximately 170 km from the Mexico-USA border. Sixteen isolates were obtained in total. Using colony morphology and sequencing the internal transcribed spacers (ITS) 1 and 4 of 18S rDNA, 14 strains were identified as Trichoderma harzianum, T. koningiopsis and T. virens. Subsequently, their antagonistic activity against M. phaseolina was evaluated in vitro, and 11 isolates showed antagonism by competition and stopped M. phaseolina growth. In 4 of these isolates, the antibiosis phenomenon was observed through the formation of an intermediate band without growth between colonies. One strain, HTE808, was identified as Trichoderma koningiopsis and grew rapidly; when it came into contact with the M. phaseolina colony, it continued to grow and sporulated until it covered the entire petri dish. Microscopic examination confirmed that it has a high level of hyperparasitism and is thus considered to have high potential for use in the control of this phytopathogen.


Subject(s)
Antibiosis/microbiology , Antibiosis/physiology , Antibiosis/prevention & control , Ascomycota/microbiology , Ascomycota/physiology , Ascomycota/prevention & control , Mexico/microbiology , Mexico/physiology , Mexico/prevention & control , Plant Diseases/microbiology , Plant Diseases/physiology , Plant Diseases/prevention & control , Sorghum/microbiology , Sorghum/physiology , Sorghum/prevention & control , Trichoderma/microbiology , Trichoderma/physiology , Trichoderma/prevention & control , Zea mays/microbiology , Zea mays/physiology , Zea mays/prevention & control
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