Our investigation suggests that endophytic Actinomycetes associated with medicinal plants can be used as bioinoculants for developing safe, efficacious and environment-friendly biocontrol strategies in the near future.
Actinomycetes are a major group of beneficial microbes, which can be explored as spanking alternative to chemical fungicides for providing defense against phytopathogens. Rhizoctonia solani is a major havoc causing severe loss to many crops. Biological measures for fungal disease management are desired over the available chemical/synthetic fungicides owing to their safety towards nontarget organisms. In the present study, 34 actinomycetes were isolated from vermicompost. Out of them, twelve revealed antifungal activity related to Indole acetic acid (IAA) production, siderophores and plant growth promotion. Under greenhouse and field conditions, these potent strains remarkably enhanced yield attributes and disease diminution as compared to untreated control. A significant disease reduction of 47-63 % against R. solani was observed in tomato plants pretreated with actinomycetes. Furthermore, induction in defense related enzymes such as peroxidase, polyphenol oxidase, phenylalanine ammonia lyase, accumulation of phenolics and flavonoids were also observed in actinomycetes treated plants. Morphological and molecular characterization analysis identified these potent isolates as Streptomyces sp. NBM3, Streptomyces sp. NBM2, Streptomyces sp. NBM1, Streptomyces sp. NBM12 and Streptomyces sp. NBM8. The present findings suggest that these microbes can be utilized for significant enhancement of plant growth and augmentation of defense related enzymes in order to cope up with R. solani induced stress, thereby contributing to crop health.
The ability of Streptomyces species to act as biocontrol agents for plant pathogens via induced systemic resistance has been demonstrated and considerable efforts have been made in elucidating the underlying mechanisms of Streptomyces-host plant-phytopathogen interactions. Here, we have assessed the ability of Streptomyces coelicolor, Streptomyces griseus, Streptomyces albus, Streptomyces antibioticus and Streptomyces champavatii to provide disease protection against Rhizoctonia solani in Solanum lycopersicon and have also examined associated changes in hydrogen peroxide (H 2 O 2 ) production, lipid peroxidation (LPO) and antioxidant enzymes. The production of H 2 O 2 at the second day after pathogen inoculation (dapi) was observed to be 1.1-fold higher in Streptomyces-treated plants, when compared to untreated inoculated control plants. A similar increase in catalase and ascorbate peroxidase activity was observed at fourth dapi whereas increased activities of guaiacol reductase and glutathione peroxidase were observed at fifth dapi. Likewise, LPO reached a maximum at sixth dapi in untreated inoculated plants while in Streptomyces-treated plants it was observed to be 1.3-1.5-fold less when compared to untreated inoculated control plants. This study offers novel insights into the mechanisms of priming by Streptomyces and highlights their capacity to activate plant defence responses generated by biotic stress through induction of antioxidant enzymes along with improved reactive oxygen species management.
Plant growth promotory Pseudomonas strains were isolated from root nodules of five plant species, viz., Trifolium pretense, Cicer arietinum, Amaranthus polygamus, Vigna mungo, and Trigonella foenum; that plants were denizen of Shekhawati region of Rajasthan. A total of 8 bacterial isolates were evaluated for growth promotion using PGP properties. Partial 16S rDNA sequencing data showed that these 8 bacterial isolates belonged to genus Pseudomonas. MEGA 4.0.2, software was used to construct a neighbor joining tree by employing boot strap method. Result exhibited significant diversity among recovered Pseudomonas strains.
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