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Abstract
The effect of osmotic stress on mycelial growth was determined for melanized and nonmelanized strains of Gaeumannomyces graminis var. tritici and var. graminis using a minimal salts medium, both in liquid and solid form. The osmotica used were KCl and sucrose. Growth measurements obtained from mycelia grown in solid media bore no obvious relationship to data obtained from liquid media at 25 C. In liquid media, all four strains exhibited minimum growth rates at the highest osmotic potential (-0.39 MPa). In solid media, minimum growth rates were measured at the lowest osmotic potential (-4.34 MPa). Addition of sucrose to liquid media doubled the growth rates of all strains, but no similar increase in growth rate was observed in solid media supplemented with sucrose. A suboptimal growth temperature (30 C) for the G. g. var. tritici strains increased the level of osmotic stress tolerated by these strains. This was not observed for the G. g. var. graminis strains. There was no consistent relationship between melanization and osmotic stress.