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Poster: Biology & Disease Mgmt: Mycology


Standardizing water potential of salt-amended growth media at different temperatures for microbiological studies
I. AUJLA (1), T. Paulitz (2) (1) Department of Plant Pathology, Washington State University, U.S.A.; (2) USDA-ARS, Washington State University, U.S.A.

Temperature and moisture profoundly influence the activity of fungi. Water potential (a measure of available water) for optimal growth of a fungi may differ with temperature. Depending on the habitat and life stage of the fungus, different components of the water potential (WP) become important. The matric component of WP dominates in soil but following plant infection, osmotic effects are important. Nutrient media amended with NaCl or KCl and polyethylene glycol (PEG) are used to study the response of fungi to osmotic and matric potentials, respectively. The advent of more precise WP measuring devices such as WP4C (Decagon Devices, Pullman, WA), using the chilled-mirror dew point technique, allowed us to standardize salt-amended potato dextrose broth with or without agar for a range of basal nutrient media from -0.2 to -9 MPa at 20°C, using NaCl and KCl for osmotic potential and PEG-8000 for matric potential. The same salt and nutrient media combinations standardized at 20°C were also measured for WP at 15, 25, 30 and 35°C. WP was extrapolated for 4 and 10°C with linear/curvilinear regression due to the temperature range limits of the instrument between 15 and 40°C. These standardized tables are more accurate than previous literature due to technological advancements and will be useful for studying the response of different life stages of fungi to osmotic and matric potential.