|Fuller Schaefer, Cynthia|
Submitted to: American Society of Sugarbeet Technologists
Publication Type: Proceedings
Publication Acceptance Date: 5/1/2007
Publication Date: 7/1/2007
Citation: Jaronski, S., Fuller Schaefer, C.A., Larson, B., Jacobsen, B.J. 2007. In vitro compatibility between three bacterial sugarbeet disease-control agents and the entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana. Proceedings, 34th Biennial Meeting American Society of Sugarbeet Technologists, February 28-March 3, 2007, Salt Lake City, Utah. p. 206-210. Interpretive Summary: The experiments reported here indicate general biological compatibility between several entomopathogenic fungi and three bacteria being developed for the control of sugarbeet root maggot, and sugarbeet pathogens, respectively. Once of the three bacteria strongly inhibit3ed germination of the fungal spores, which indicates potential incompatibility in actual use in the crop; the two others did not. While vegetative growth of the Beauveria fungus was inhibited by two of the bacteria, this situation occurred only on a medium favoring the bacteria over the fungus, and is probably not representative of interactions in nature. Furthermore, inhibition of vegetative growth has relevancy only if one desires that the Beauveria would colonize the sugarbeet root surface.
Technical Abstract: The rhizosphere is the primary arean for entomopathogenic fungi (EPF) deployed against soil-dwelling pests, and is also the site of action of biological agents used against root pathogens. Interactions between EPF and soil microbes, much less biofungicidal agents, have been barely studied, however, USDA / ARS has been developing a biocontrol strategy using EPF against the sugarbeet root maggot, in parallel with Montana Sate University efforts to develop three micvrobial agents against the various sugarbeet pathogens: Bacillus pumilis LS201 (against Pythium, Aphanomyces), B. mohaviensis MSU127 (against Rhizoctonia), and B. mycoides BmJ (against Cercospora beticola). We examined the effect of the three biofungicidal agents on conidial germination and pyphal growth of three isolates of the EPF, (GHA, TM28, TM86), on Plate Count Agar, Tryptic Soy Agar, and Potato Dextrose Agar. Conidial germination: There were considerable differences between the two fungal species and among isolates within each species in sensitivity to the bacteria. MSU127 had the strongest, most consistent inhibition with zones as wide as 16 mm, which persisted for at least several months. Hyphal growth: Only Beaveria GHA was affected, by BmJ and LS201, on only TSA. The medium affected the message – depending upon the medium used, very different inhibitory patterns were observed. This research was partially supported by CSREES NRI grant 2001-353-16-11109.