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. This study aimed to evaluate the biocontrol potential of bacteria isolated from different plant species and soils. The mechanisms through which these bioagents operate are either by direct action against the pathogen i.e., antagonism which includes parasitism, antibiosis, competition, and/or. Bacterial genera such as Bacillus and Pseudomonas may be potential reservoirs of biocontrol agents for effectively suppressing soil inhabiting root pathogens.
Most bacterial isolates with biocontrol potential were isolated from rhizospheric soil. Bacteria from different plant species (rhizosphere or phylloplane) exhibited differences in the ability to produce the compounds evaluated. 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. Proteolytic activity was most frequently observed among the bacterial isolates.
Screening of bacterial endophytes as potential biocontrol agents against soybean diseases: Authors: de Almeida Lopes, Karla Bianca Carpentieri-Pipolo, Val&233 ria Fira, Djordje Balatti, Pedro Alberto L&243 pez, Silvina Marianela Yanil Oro, Thiago Henrique Stefani Pagliosa, Eduardo Degrassi, Giuliano: Keywords:Concerns regarding food safety and the environment have led to reduced use of agrochemicals and the development of sustainable agriculture. Pliego, Clara Ramos, Cayo de Vicente, Antonio. 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.Screening for candidate bacterial biocontrol agents against soilborne fungal plant pathogens 2011.
The antagonistic effect of microorganism is the result of interaction among the microbial populations. It was reported that antagonistic bacteria act as a biocontrol agent due to their ability of the different modes of action 12. Dual culture plate assay is.metabolites. 1 However, efficient antagonists must be obtained for biological control to become a reality.In vitro screening for inhibition of mycelial growth of phytopathogenic fungi by bacterial isolates is the first step in selecting putative bacterial biocontrol agents.
3Several organisms have been demonstrated to be effective against. 2 Of these, some bacteria positively affect plants and have been designated as plant growth-promoting rhizobacteria (PGPR). Bacteria are estimated to occupy between 7% and 15% of the total root surface area.
In addition, bacteria that colonize the shoots have a better chance of surviving and multiplying in a nutrition-rich environment such as the soil, whereas in the phylloplane, they are exposed to high temperatures, moisture content fluctuations, and limited nutrient availability.In vivo biocontrol agent selection is not a simple task due to the diversity of agents and interactions with the host plant, and therefore, efficient search methods are required. 7 Kishore et al., 8 found that both rhizoplane and phylloplane bacteria promote peanut seedling growth. 4–6In addition to the rhizosphere, the phylloplane is a source of antagonists however, bacteria from this area are still underused as biological control agents, especially compared to rhizobacteria. Directly, they solubilize minerals and cause a wide range of changes in the rhizosphere, which promotes higher efficiency in the absorption of water and macro- and micronutrients by plants and changes in phytohormone concentrations, nitrogen fixation, and siderophore production. Indirectly, they suppress pathogens mediated by competition and the production of antimicrobial compounds and lytic enzymes.
The bacteria were obtained from different niches (phylloplane, rhizosphere, and soil) and grouped according to their isolation source: fig tree ( Ficus carica L. Material and methods Origin of the bacteriaA total of 1219 bacteria that belonged to the collection of the Plant Bacteriology Laboratory (Laboratório de Bacteriologia Vegetal – LBV) at the Universidade Federal de Pelotas, Brazil, were used. Thus, due to the need for alternative management strategies for difficult-to-control pathogens, and considering that the initial steps for biocontrol agent selection should be performed in the absence of the host, the present study aimed to (i) characterize bacteria to determine their in vitro potential for the production of compounds related to phytopathogen biocontrol and/or promotion of plant growth (CRBPGs) (ii) select bacterial isolates with the highest number of CRBPGs and (iii) validate the selection process by studying the effect of the bacteria selected on the ringed peach nematode. 10,11In this sense, in vitro tests are appropriate during the initial selection steps due to the large number of microorganisms that can be evaluated and, especially, their low cost. In recent years, this concept has evolved, and other groups of researchers have proposed initial selection criteria based on evaluations in the absence of the host. In 1997, Schisler and Slininger 9 divided the selection process into three categories: (i) choosing the appropriate pathosystem, (ii) choosing the adequate method, and (iii) characterizing the isolates and evaluating efficiency.
Four bacteria arranged equidistant at the edges were streaked on each Petri dish containing 523 medium 12 and in the center, a mycelial disk containing the fungus previously grown in a potato dextrose agar (PDA). Bacteria that previously exhibited or did not exhibit the ability to produce each compound studied were used as positive and negative controls, respectively.The ability of bacteria to produce antibiotic compounds against Monilinia fructicola (Winter) Honey, the causal agent of peach brown rot was evaluated. Evaluation of CRBPG productionThe abilities to produce antimicrobial compounds (antibiosis and ammonia production) and hydrolytic enzymes (amylases, lipases, proteases, and chitinases) and to solubilize phosphates were evaluated. (51), non-rhizospheric soil (309), and others (65 – tomato plant ( Solanum lycopersicum L.), Brassicae, and culture medium contaminants).
The ringed nematode ( Mesocriconema xenoplax (Raski) Loof and de Grisse) species associated with Peach Tree Short Life disease was chosen as the target species to evaluate the efficiency of bacterial biocontrol.Mobile forms (juvenile and adult) of the nematode (25 per plot) were treated with a bacterial suspension ( A 540 = 0.5) or with saline solution (control) at a 1:1 ratio (v/v). Validation of biocontrol bacterial selection – evaluation of nematicide activityAt this step, the bacteria that produced at least five of the eight CRBPGs analyzed were used, as well as DFs1985 (which did not produce any of the compounds evaluated) and DFs2180 (which produced one compound), for contrast effects. The intensity of production was low for positive reaction after 10 (lipids and proteins) or 21 days (chitin) of incubation middle if the positive reaction happened after 14 days of incubation (chitin) and high when the positive reaction occurred after four (lipids and proteins) or seven days of incubation (chitin).
Partial amplicom of 16S rRNA of samples were produced by PCR with primers 27F and 1492R. Total DNA was extracted with Wizard genomic DNA purification Kit (Promega Corporation, USA). 19 Bacterial identificationThe bacteria with best control were identificated by their 16S rRNA sequences. 18 The values were sin acscx/100 transformed, subjected to analysis of variance, and grouped by the method of Scott and Knott. The number of dead nematodes was evaluated by adding 10 μL of 1 N NaOH, according to Chen and Dickson.
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