This Is AuburnElectronic Theses and Dissertations

Characterization of root colonization by the biocontrol bacterium Bacillus firmus strain GB126




Durham, Mark

Type of Degree



Entomology and Plant Pathology


A new biological control treatment for plant-parasitic nematodes was marketed throughout the U.S. starting in 2010. The treatment consists of the biocontrol agent Bacillus firmus strain GB126. Following commercial release of the treatment, questions arose about the persistence of GB126 during the growing season. The work reported in this thesis was designed to address this key question by developing techniques to monitor root colonization of GB126. To accomplish this, root printing and dilution plating techniques were developed to monitor root colonization of GB126. Results showed that GB126 colonized the roots of several plant species and colonized soybean in soils ranging from pH 5.05 to 7.05. More importantly, GB126 was isolated from the rhizoplane and endorhiza of plant roots at extended periods after seed inoculation. The results of this study show that GB126 can persist externally and internally on roots following application as a seed treatment.