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Rhizospheric Actinomycetes Revealed Antifungal and Plant-Growth-Promoting Activities under Controlled Environment

ABSTRACT: Actinomycetes has large habitats and can be isolated from terrestrial soil, rhizospheres of plant roots, and marine sediments. Actinomycetes produce several bioactive secondary metabolites with antibacterial, antifungal, and antiviral properties. In this study, some Actinomycetes strains were isolated from the rhizosphere zone of four different plant species: rosemary, acacia, strawberry, and olive. The antagonistic activity of all isolates was screened in vitro against Escherichia coli and Bacillus megaterium. Isolates with the strongest bioactivity potential were selected and molecularly identified as Streptomyces sp., Streptomyces atratus, and Arthrobacter humicola. The growth-promoting activity of the selected Actinomycetes isolates was in vivo evaluated on tomato plants and for disease control against Sclerotinia sclerotiorum. The results demonstrated that all bacterized plants with the studied Actinomycetes isolates were able to promote the tomato seedlings’ growth, showing high values of ecophysiological parameters. In particular, the bacterized seedlings with Streptomyces sp. and A. humicola showed low disease incidence of S. sclerotiorum infection (0.3% and 0.2%, respectively), whereas those bacterized with S. atratus showed a moderate disease incidence (7.6%) compared with the positive control (36.8%). In addition, the ability of the studied Actinomycetes to produce extracellular hydrolytic enzymes was verified. The results showed that A. humicola was able to produce chitinase, glucanase, and protease, whereas Streptomyces sp. and S. atratus produced amylase and pectinase at high and moderate levels, respectively. This study highlights the value of the studied isolates in providing bioactive metabolites and extracellular hydrolytic enzymes, indicating their potential application as fungal-biocontrol agents.

SUBMITTER: Elshafie H

PROVIDER: S-EPMC9317816 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:In this research, the biosynthetic and biocontrol potential of endophytic yeast to improve the growth and development of tobacco has been elucidated. Three yeast strains were enriched and isolated from different plant tissues. Partial sequence analysis of ITS5-5.8-ITS4 region of the nuclear ribosomal DNA with universal primers identified YD5, YE1, and YSW1 as Saccharomyces cerevisiae (S. cerevisiae), Zygosaccharomyces bailii (Z. bailii), and Saccharomyces kudriavzevii (S. kudriavzevii), respectively. When cultivated in a medium supplemented with 0.1% L-tryptophan, isolated yeast strains produced indole-3-acetic acid (IAA). The capacities of those strains to improve the mobility of phosphorus and synthesize siderophores has been proven. Their antimicrobial activities against several Solanaceae plant pathogenic fungi (Alternaria solani pathovar. tobacco, Rhizoctonia solani, and Fusarium solani pathovar. phaseoli) were determined. S. cerevisiae YD5, Z. bailii YE1, and S. kudriavzevii YSW1 inhibited the growth of all tested pathogens. Yeast strains were tested for endophytic colonization of tobacco by two different inoculation methods: soil drench (SD) and leaf spraying (LS). To establish colonization in the various tissues of tested tobacco (Nicotiana tabaccum L.) plants, samples were taken on the seventh, fourteenth, and twenty-first days after treatment (DAT), and explants were inoculated on yeast malt agar (YMA). Both techniques of inoculation showed a high frequency of colonization from 83.33% to 100%. To determine the effectiveness of the microbial endophytes, their effect on some physiological processes in the plant were analyzed, such as photosynthesis, stomatal conductivity, and transpiration intensity. The effect of single and double treatment with yeast inoculum on the development and biochemical parameters of tobacco was reported. Plants have the ability of structural and functional adaptation to stress effects of different natures. All treated plants had a higher content of photosynthetic pigments compared to the control. Photosynthesis is probably more intense, and growth stimulation has been observed. The chlorophyll a/b ratio remained similar, and the total chlorophyll/carotenoid ratio slightly increased as a result of elevated chlorophyll levels. The most significant stimulating effect was recorded in tobacco plants treated by foliar spraying with Z. bailii YE1 and S. cerevisiae YD5. In contrast, S. kudriavzevii YSW1 had a better effect when applied as a soil drench. Thus, S. cerevisiae YD5, Z. bailii YE1, and S. kudriavzevii YSW1 have a high potential to be used as a biocontrol agents in organic agriculture.

Project description:In this study 98 rhizospheric actinomycetes were isolated from different wheat and tomato fields, Punjab, Pakistan. The isolates were characterized morphologically, biochemically, and genetically and were subjected to a comprehensive in vitro screening for various plant growth promoting (PGP) traits. About 30% of the isolates screened were found to be the promising PGP rhizobacteria (PGPRs), which exhibited maximum genetic similarity (up to 98-99%) with different species of the genus Streptomyces by using16S rRNA gene sequencing. The most active indole acetic acid (IAA) producer Streptomyces nobilis WA-3, Streptomyces Kunmingenesis WC-3, and Streptomyces enissocaesilis TA-3 produce 79.5, 79.23, and 69.26 μg/ml IAA respectively at 500 μg/ml L-tryptophan. The highest concentration of soluble phosphate was produced by Streptomyces sp. WA-1 (72.13 mg/100 ml) and S. djakartensis TB-4 (70.36 mg/100 ml). All rhizobacterial isolates were positive for siderophore, ammonia, and hydrogen cyanide production. Strain S. mutabilis WD-3 showed highest concentration of ACC-deaminase (1.9 mmol /l). For in-vivo screening, seed germination, and plant growth experiment were conducted by inoculating wheat (Triticum aestivum) seeds with the six selected isolates. Significant increases in shoot length was observed with S. nobilis WA-3 (65%), increased root length was recorded in case of S. nobilis WA-3 (81%) as compared to water treated control plants. Maximum increases in plant fresh weight were recorded with S. nobilis WA-3 (84%), increased plant dry weight was recorded in case of S. nobilis WA-3 (85%) as compared to water treated control plants. In case of number of leaves, significant increase was recorded with S. nobilis WA-3 (27%) and significant increase in case of number of roots were recorded in case of strain S. nobilis WA-3 (30%) as compared to control plants. Over all the study revealed that these rhizospheric PGP Streptomyces are good candidates to be developed as bioferlizers for growth promotion and yield enhancement in wheat crop and can be exploited for the commercial production of different agro-active compounds.

Project description:Wheat crops require effective nitrogen fertilization to produce high yields. Only half of chemical N2 fertilizers are absorbed into plants while the rest remains in the soil, causing environmental problems. Fungi could maximize nitrogen absorption, and from an environmental and biodiversity point of view, there is an urgent necessity for bioprospecting native fungi associated with wild plants growing in harsh environments, e.g., St. Katherine Protectorate (SKP) in the arid Sinai. Recovered taxa, either endophytic and/or rhizospheric, were screened for their plant growth-promoting (PGP) traits. Eighteen fungal isolates (15 rhizospheric and 3 endophytic) belonging to anamorphic ascomycetes were recovered from 9 different wild plants, and their PGP traits (indole-3-acetic acid [IAA] production, phosphate solubilization, siderophore production, and hydrolytic enzyme production) were measured. Rhizospheric isolate NGB-WS14 (Chaetosphaeronema achilleae) produced high levels of IAA (119.1 μg mL-1) in the presence of tryptophan, while NGB-WS 8 (Acrophialophora levis) produced high IAA levels (42.4 μg mL-1) in the absence of tryptophan. The highest phosphate-solubilizing activity (181.9 μg mL-1) was recorded by NGB-WFS2 (Penicillium chrysogenum). Endophytic isolate NGB-WFE16 (Fusarium petersiae) exhibited a high percentage level of Siderophore Unit (96.5% SU). All isolates showed variability in the secretion of extracellular hydrolytic enzymes. Remarkably, all isolates had antagonistic activity (55.6% to 87.3% suppression of pathogen growth) against the pathogenic taxon Alternaria alternata (SCUF00001378) in the dual-assay results. Out of the 18 isolates, 4 rhizospheric and 1 endophytic isolate showed significant increases in shoot dry weight and shoot nitrogen and chlorophyll content of wheat plants subjected to low inputs of chemical nitrogen (N) fertilizers (50% reduction) compared with the non-inoculated control in a pot experiment. Potent taxa were subjected to sequencing for molecular confirmation of phenotypic identification. The retrieved ITS sequences in this study have been deposited in GenBank under accession numbers from LC642736 to LC642740. This study considered the first report of endophytic fungi of Cheilanthes vellea, a wild plant with PGPF which improves wheat growth. These results recommend using PGPF as inoculants to alleviate low nitrogen fertilization.

Project description:Endophytic actinomycetes have shown unique plant growth promoting as well as antagonistic activity against fungal phytopathogens. In the present study forty-two endophytic actinomycetes recovered from medicinal plants were evaluated for their antagonistic potential and plant growth-promoting abilities. Twenty-two isolates which showed the inhibitory activity against at least one pathogen were subsequently tested for their plant-growth promoting activities and were compared genotypically using DNA based fingerprinting, including enterobacterial repetitive intergenic consensus (ERIC) and BOX repetitive elements. Genetic relatedness based on both ERIC and BOX-PCR generates specific patterns corresponding to particular genotypes. Exponentially grown antagonistic isolates were used to evaluate phosphate solubilization, siderophores, HCN, ammonia, chitinase, indole-3-acetic acid production, as well as antifungal activities. Out of 22 isolates, the amount of indole-3-acetic acid (IAA) ranging between 10-32 ?g/ml was produced by 20 isolates and all isolates were positive for ammonia production ranging between 5.2 to 54 mg/ml. Among 22 isolates tested, the amount of hydroxamate-type siderophores were produced by 16 isolates ranging between 5.2 to 36.4 ?g/ml, while catechols-type siderophores produced by 5 isolates ranging from 3.2 to 5.4 ?g/ml. Fourteen isolates showed the solubilisation of inorganic phosphorous ranging from 3.2 to 32.6 mg/100ml. Chitinase and HCN production was shown by 19 and 15 different isolates, respectively. In addition, genes of indole acetic acid (iaaM) and chitinase (chiC) were successively amplified from 20 and 19 isolates respectively. The two potential strains Streptomyces sp. (BPSAC34) and Leifsonia xyli (BPSAC24) were tested in vivo and improved a range of growth parameters in chilli (Capsicum annuum L.) under greenhouse conditions. This study is the first published report that actinomycetes can be isolated as endophytes from within these plants and were shown to have antagonistic and plant growth promoting abilities. These results clearly suggest the possibility of using endophytic actinomycetes as bioinoculant for plant growth promotion, nutrient mobilization or as biocontrol agent against fungal phytopathogens for sustainable agriculture.

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Rhizospheric Actinomycetes Revealed Antifungal and Plant-Growth-Promoting Activities under Controlled Environment

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