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ARS Home » Midwest Area » Urbana, Illinois » Soybean/maize Germplasm, Pathology, and Genetics Research » Research » Publications at this Location » Publication #79827
Title: FLOW CYTOMETRIC ANALYSIS OF CONIDIA OF FUNGI ISOLATED FROM SOYBEAN VASCULARTISSUE

Author
item GOURMET, CATHERINE - UNIV OF ILLINOIS
item Gray, Lynn
item RAYBURN, ALBERT - UNIV OF ILLINOIS

Submitted to: Journal of Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/6/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Brown stem rot is an important soybean disease that is caused by a fungal pathogen called Phialophora gregata. This fungus produces very small spores called conidia. Conidia from different individuals (called isolates) of the fungus all look the same when examined with a microscope. A method was needed that could be used to determine if there were differences in the spores from individuals of the fungus that were collected from different grower fields. Spores from different individuals of the fungus were obtained from different farmer's fields and were stained with a fluorescent dye called propidium iodide. Samples of stained spores of each individual were examined with an instrument called a flow cytometer that measures the intensity of fluorescence of each individual spore. It was found that there were differences in intensity of fluorescence of stained spores of different individuals. These differences in fluorescence intensity could then be used to group individuals of the fungus. This fluorescence technique is fast and large numbers of individuals of the fungus can be sampled in a short period of time to categorize isolates collected from different grower's fields. This fluorescence technique should be useful to soybean plant pathologists and mycologists for rapidly distinguishing different individuals of this important soybean pathogen.

Technical Abstract: Flow cytometry was used to characterize isolates of Phialophora gregata using the fluorescence intensity of propidium iodide-stained conidia. Fungal isolates of P. gregata differed in their mean fluorescence intensity, ranging from 100.0 to 129.7 arbitrary units (AU's). When the number of fluorescent events was plotted against intensity of fluorescence, a single peak was observed. Fluorescent patterns of Acremonium species fungi isolated from soybean vascular tissue were compared to isolates of P. gregata. Their mean fluorescence intensity ranged from 76.4 to 88.0 (AU). With some of these isolates, multiple peak histograms were observed corresponding to multiple spore sizes as well as single and double nucleated conidia. Using flow cytometry, we were able to distinguish P. gregata isolates from Acremonium species fungi isolated from soybean vascular tissue, based on mean fluorescence intensity and/or the presence of multiple peaks. Flow cytometric analysis of propidium-iodide stained conidia of Phialophora isolates should be useful for rapidly distinguishing this fungus from other soybean vascular fungi.