Isolation of Possible Biocontrol Endophytic Bacteria from Solanum tuberosum Effective Against Streptomyces scabies.

Use of biological control offers a cost effective and environmentally safe method for controlling plant diseases. Biocontrol agents that can colonize roots and live endophytically within plant tissue should allow for effective disease control. The goal of this research was to develop protocols to isolate putative Streptomyces species from potato stem and tuber tissue due to their ability to produce inhibitory compounds which could potentially reduce diseases caused by Streptomyces scabies. Endophyte isolation from Solanum tuberosum (potato) plants (stem and tuber tissues) that were grown in a biocontrol field trial were the focus of this study. Several surface sterilization processes were assessed and two different tissue-processing methods were focused on to obtain endophytes: 1) excising cross-sections of stem tissue and 2) use of a maceration technique for tuber and stem tissue. From the stem tissue, four putative Streptomyces species were isolated; one of the four isolates was inhibitory to Streptomyces scabies in agar plate bioassays. To date, two putative Streptomyces species and several other bacterial species were isolated from tuber tissue. Further characterization of these isolates are underway with the goal of discovering endophytic pathogen-inhibiting bacteria that could then be used in concert with soil-dwelling biocontrol agents to enhance disease control of the potato scab pathogen

Use of Two Pathogen-inhibiting Streptomyces Isolates for Biocontrol of Scab Disease of Raphanus sativus

Streptomyces species are ubiquitous soil bacteria that are promising as biological control agents due to their prolific antibiotic production that can inhibit soil-borne plant pathogens. This includes Streptomyces scabies, which causes scab disease on underground storage organs. The goal of this research was to test two Streptomyces isolates that have known inhibitory and biocontrol abilities against S. scabies in a potato (Solanum tuberosum) agricultural system for their effectiveness in biocontrol of this pathogen in a radish (Raphanus sativus) greenhouse assay. Pathogenic S. scabies were mixed into either pasteurized or unpasteurized soil prior to planting. Radish seeds or radish roots were soaked in a spore suspension of the two biocontrol Streptomyces isolates. Controls of treatments without the pathogen and the biocontrol Streptomyces were included. Radish plants were grown to maturity. Upon harvesting, the radish taproot was rated for scab disease and tuber weight and length were determined. Disease levels were reduced in the presence of the two biocontrol Streptomyces. Taproot weight was greater in the treatments that included the biocontrol Streptomyces. In addition, evidence was sought to determine the ability of these Streptomyces isolates and other pathogen-inhibiting bacteria to enter into an endophytic relationship with the radish plant. For this, several protocols were assessed to try to optimize the isolation of endophytic bacteria from stem and taproot tissue. Surface-sterilized tissue sections (stem and taproot) or macerated stem tissue spread on agar plates have indicated the presence of several bacterial endophytes, including two putative Streptomycete isolates from the stem tissue sections. The search for additional endophytic bacteria capable of inhibiting the scab pathogen are currently underway. The results of this study are promising for the use of these Streptomyces isolates for biocontrol against scab disease in radish

Arctic moistening provides negative feedbacks to riparian plants

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