Growth Promotion and Biocontrol Activity of Endophytic Streptomyces spp.

There has been many recent studies on the use of microbial antagonists to control diseases incited by soilborne and airborne plant pathogenic bacteria and fungi, in an attempt to replace existing methods of chemical control and avoid extensive use of fungicides, which often lead to resistance in plant pathogens. In agriculture, plant growth-promoting and biocontrol microorganisms have emerged as safe alternatives to chemical pesticides. Streptomyces spp. and their metabolites may have great potential as excellent agents for controlling various fungal and bacterial phytopathogens. Streptomycetes belong to the rhizosoil microbial communities and are efficient colonizers of plant tissues, from roots to the aerial parts. They are active producers of antibiotics and volatile organic compounds, both in soil and in planta, and this feature is helpful for identifying active antagonists of plant pathogens and can be used in several cropping systems as biocontrol agents. Additionally, their ability to promote plant growth has been demonstrated in a number of crops, thus inspiring the wide application of streptomycetes as biofertilizers to increase plant productivity. The present review highlights Streptomyces spp.-mediated functional traits, such as enhancement of plant growth and biocontrol of phytopathogens

In vitro characterization of plant growth promoting and biocontrol activity of beneficial microorganisms

Plant roots are associated with numerous and diverse types of beneficial and pathogenic microorganisms. Among them, plant growth\u2013promoting (rhizo)bacteria (PGPB or PGPR) are isolated from plants crops worldwide, and many of them are used as agricultural inoculants. Agricultural biofertilization and biocontrol of pathogens are eco-friendly alternatives to chemical usage and have less energy, environmental, and economic costs. PGPB isolation and evaluation are essentials steps for determining bacteria that could improve plant development and productivity. In the present study three Streptomyces sp. strains SB14, SA51 & SL81, two Pseudomonas sp. strains PT65 & PN53, an Agrobacterium sp. strain AR39 and an internal control (IC) Pseudomonas synxantha were evaluated in vitro for different plant growth promoting and biocontrol activities. The results were aimed to identify possible antagonists able to inhibit different plant bacterial (Xanthomonas vesicatoria, Clavibacter michiganensis subsp. michiganensis, Clavibacter michiganensis subsp. sepedonicus, Acidovorax citrulli and Ralstonia solanacearum) and fungal (Rhizoctonia solani, Sclerotium sp., Fusarium oxysporum, Alternaria solani and Monilia laxa) pathogens. All the strains were screened for biocontrol activity on three different media\u2019s and AIA (average inhibition area) was calculated. Among the isolates, each strain showed different ability to inhibit the pathogens: Streptomyces sp. strain SA51 was found to be most active. The most prospective strains SA51, AR39 and DLS65 were further evaluated in the field, as possible biocontrol agents for the tomato spot disease (X. vesicatoria), singularly and as a consortium. Results will improve our understanding on the use of such microbial biocontrol agents and will implement innovative biocontrol strategies to bacterial diseases

Draft genome sequence of plant growth-promoting Streptomyces sp. strain SA51, isolated from olive trees

A streptomycete was isolated from the rhizosphere of olive trees in autumn 2004. Its molecular characterization showed the presence of metabolic pathways promoting plant growth and additional properties, thus indicating such strain as a prospective agent for future biocontrol applications in planta. We report here the whole genome sequence of Streptomyces avermitilis, strain SA51