Date of Award

8-2014

Degree Type

Thesis

Degree Name

Master of Science

Department

Biology

Program

Biology

First Advisor/Chairperson

Dr. Donna Becker

Second Advisor

Alan Rebertus

Third Advisor

Josh Sharp

Abstract

Potato marketability and tuber quality can be decreased upon infection by a pathogen, Streptomyces scabies. Current disease control consists of expensive irrigation systems and using hazardous chemicals, which exert limited disease control and are potential hazards to those exposed. Biological control offers a cost effective method for controlling disease. Antibiotic producing Streptomyces have indicated their ability to combat plant diseases. Some Streptomyces species colonize within plant tissues without causing disease symptoms (endophytes). This research sought for the presence of endophytic Steptomyces or closely related species in potato plants that were grown in fields containing pathogen-inhibiting Streptomyces. To establish genus level identification of the endophytes, the 16S rRNA gene was sequenced. To assess inhibition abilities of endophytes against the pathogen, double layer antibiotic assays were done by spot inoculating endophytes and overlaying agar with the pathogen. Multiple layer agar plates were used to test the paired interactions among endophyte isolates on their ability to use quorum sensing to enhance antibiotic production to inhibit the pathogen. In each assay zones of inhibition were measured. From distinct potato stem tissues, four putative, Streptomyces strains were isolated. The 16S rRNA sequencing indicated a 99% match to Microbispora, closely related to the Streptomyces genus. Our results demonstrated that an isolate (called 1) could inhibit the pathogenic strain 87. Isolate 1 also produced zones of reduced growth of the pathogen in pairwise combinations with the other 3 isolates. This research is among the initial studies that are trying to utilize endophytes for biological control agents.

Included in

Agriculture Commons

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