Effect Of Antagonistic Bacteria Research Articles

Effect of antagonistic bacteria and its formulation to control fusarium wilt disease on shallot

Biocontrol of pathogenic fungi using antagonistic bacteria isolated from the soil (rhizosphere) is expected to suppress plant diseases to obtain good quality of yield, and thus support sustainable agriculture. The study aimed to formulate and scale up the production of rhizosphere-based bacterial biopesticides that effective in suppressing the onset of Fusarium wilt disease caused by Fusarium oxysporum f.sp. cepae on shallot. The experiment to evaluate the effectiveness of biocontrol agents against Fusarium wilt disease was carried out employing shallot cv. ‘bima curut’ in the field (Patrol-Indramayu,West Java), from May to August 2018 growing season. The experimental plot of 1.20 m x 18 m, was prepared using plant spacing of 15 × 10 cm. The solid formulation of kaolin-based bacteria (containing bacterial cells of 109 CFU/mL) was applied with variation of four concentrations range from 0.3125 to 2.5 mL/L. The experiment was arranged in randomized block design with four replications. Shallot beginning at 30 days old-plant was sprayed three times at one-week intervals. The results showed that the disease intensity was significantly lower than in control. Under natural infection, the spraying application of a bacterial isolate (DSB2) using kaolin formulation (107 CFU/mL) with a formula concentration of 1.25 mL/L could reduce the disease intensity. Tuber yield of formula treatments was significantly higher than that of control. Thus, the use of bacterial formula as environmental-friendly biocontrol agent in this study might be further recommended in controlling Fusarium wilt disease on shallots.

Bacillus and Pseudomonas spp. provide antifungal activity against gray mold and Alternaria rot on blueberry fruit

Gray mold and Alternaria rot are diseases of highbush blueberry (Vaccinium corymbosum L.) fruit that develop in storage, in particular with interruption in the retail cold chain. In this study, the effect of antagonistic bacteria from the Bacillus and Pseudomonas genera was assessed on mycelial growth of Botrytis cinerea and Alternaria alternata. The bacteria were also evaluated for their suppression of gray mold and Alternaria rot on stored blueberries. Isolation of antifungal extracts and identification of antifungal compounds from bacterial strains were also performed. The results showed that various bacterial antagonists reduced mycelial growth of B. cinerea and A. alternata by up to 42 and 27%, respectively. The bacteria also provided inhibition of blueberry fruit rot by both pathogens, reducing rot incidence and severity by as much as 50 and 64%, respectively. Extracts from the Bacillus and Pseudomonas spp. reduced mycelia growth and spore germination of B. cinerea. Antifungal compounds in these bacterial extracts, including arthrofactins in some Pseudomonas spp., indicated that antibiosis is a main mechanism of action. The results of this study suggest antagonistic bacteria may represent a potential method for controlling postharvest fruit rot of blueberries.

Screening and Control Effects of Antagonistic Bacteria against Tobacco Black Shank Disease

We collected 17 soil samples from tobacco fields in Bijie City, Guizhou Province, Luzhou City, Sichuan Province. A total of 247 bacterial strains were isolated and 19 pairs of antagonism against Phytophthora nicotianae by tablet dual culture. Then six antagonistic and compatibility better bacterial strains were selected.. Further by antibacterial, pot and field experiments, come to the strain combination B41B57 and L7L47 have best inhibitory effect. At last, identified B41 as Bacillus subtilis, L7, L47 is B.amyloliquefaciens, B57 is Pseudomonas.putida by morphological observation, physiological and biochemical characteristics and 16SrDNA sequence analysis.

Stable isotope probing of amino sugars – a promising tool to assess microbial interactions in soils

Bacteria and fungi are key protagonists of litter degradation in soils. Often they have to share common substrates, which has led to special interactions between both microbial groups. Due to the historical classification of bacteriology and mycology as two separate fields of microbial research, the understanding of their interactions in soils is scares, while it is crucial for a better understanding of nutrient recycling and carbon sequestration in soils. Therefore, a new approach to investigate fungal-bacterial interactions is proposed using stable isotope probing of their amino sugar biomarkers. An agricultural soil, under different microbial inhibition treatments, was incubated for 21 days with (13)C-labeled plant residues. Residue respiration was determined by measuring the isotopic composition and concentration of the produced CO2, using an isotope ratio mass spectrometer coupled to a trace gas preparation unit. At several time points, amino sugars were extracted, after hydrolysis, from the incubated microcosms. Subsequently, (13)C-isotopic composition and concentration of the individual amino sugars was determined using liquid chromatography/isotope ratio mass spectrometry. When the bacterial community was inhibited, fungi showed an increased capacity to metabolize added plant residues indicating an antagonistic effect of bacteria towards fungi. Furthermore, the fungal community was able to take benefit of a larger portion of the residue, which indicates that this antagonism was at least partially due to interference competition. On the other hand, the inhibition of the fungal community appeared to have a very negative effect on the capacity of bacteria to metabolize added plant residues. Therefore, the bacterial community could be considered as playing a parasitic type role towards fungi during litter degradation. This newly developed methodology proved to be very useful for elucidating microbial interactions during plant residue degradation.

Characterization and application of microbial antagonists for control of Fusarium head blight of wheat caused by Fusarium graminearum using single and mixture strain of antagonistic bacteria on resistance and susceptible cultivars

Fusarium head blight (FHB) caused by Fusarium graminearum leads to significant yield losses of wheat (Triticum aestivum L.) in many provinces of Iran, especially in the northern provinces in the margin of Caspian Sea. One strategy for the control of FHB is to use antagonistic bacteria that are plant growth promoting. In order to assess the potential of phyllospheric microorganisms in biological control of FHB, one hundred and ninety isolates of Pseudomonas, Erwinia and Bacillus spp. were collected from phyllosphere of healthy and infected wheats. Among them, eight isolates were selected and purified with the most antagonistic ability against the growth of pathogenic fungal species (F. graminearum) using the dual culture method. According to the results of biochemical and physiological tests, they were identified as three biovar of Pseudomonas fluorescens, one isolate of them was Erwinia herbicola and two species of Bacillus such as Bacillus subtilis and Bacillus cereus. Production of antifungal substances and volatile metabolites, siderophores and secretion of lytic enzymes such as protease and cellulase were evaluated as the inhibitory mechanisms in vitro. Furthermore, the effects of antagonistic bacteria were studied on severity and incidence of disease caused by F. graminearum in greenhouse conditions. Statistical analysis of data indicated that wheat spikes treatment with antagonistic bacteria not only reduced the severity and incidence of disease compared with the control but also showed positive influence on growth and yield of wheat cultivars. In general, multiple isolates such as B. subtilis 1 and P. fluorescens bv. 1 and 4 together were determined as the most effective strains in reducing incidence of disease. It can be concluded that multiple antagonistic isolates have better effects of control than single isolate. Key words: Biological control, Fusarium head blight, Fusarium graminearum,Pseudomonas fluorescens, Erwinia herbicola and Bacillus subtilis.

Effect of Antagonistic Bacteria on Establishment of Honey Bee-DispersedErwinia amylovorain Pear Blossoms and on Fire Blight Control

In field trials conducted in 1991 and 1992 at Medford, OR, and in 1992 at Wenatchee, WA, Pseudomonas fluorescens strain A506 and Erwinia herbicola strain C9-1 established epiphytic populations on pear blossoms and were effective antagonists for the biological control of fire blight. Both bacterial antagonists, water, or streptomycin sulfate were applied to trees at 30% and full bloom. Pear trees were challenged inoculated with freeze-dried cells of E. amylovora vectored to blossoms by honey bees. One week after full bloom, the antagonists were established in more than 95% of treated blossoms in Oregon in 1991 and Washington in 1992, but in less than 50% of blossoms in Oregon in 1992. At the same bloom stage, 41% (Oregon, 1991), 27% (Oregon, 1992), and 49% (Washington, 1992) of water-treated blossoms had detectable populations of E. amylovora, whereas trees treated with bacterial antagonists always had a significantly lower (p 0.05) percentage of blossoms with detectable E. amylovora populations: 18-20% (Oregon, 1991), 9-15% (Oregon, 1992), and 8-17% (Washington, 1992). In Oregon in 1991, only 4% of blossoms treated with bacterial antagonists supported populations of E. amylovora that exceeded 10(5) cfu per blossom compared with 19% of blossoms treated with water; however, suppression of population size of E. amylovora by bacterial antagonists was not apparent in 1992. In 1991, fire blight symptoms developed in 8, 0.1, and 1% of blossom clusters treated with water, streptomycin, or bacterial antagonists, respectively. In 1992, the percentage of diseased blossom clusters in these same treatments in Oregon averaged 44, 2, and 22%, respectively, and 9, 2.5, and 4%, respectively, in Washington