The interactive effects of temperature and osmotic potential on the growth of marine isolates of Fusarium solani

Abstract

The mycelial growth of 18 Fusarium solani strains isolated from sea beds of the south-eastern coast of Spain was tested on potato-dextrose-agar adjusted to different osmotic potentials with either KCl or NaCl (-1.50 to -144.54 bars) in 10 degrees C intervals ranging from 15 to 35 degrees C. Fungal growth was determined by measuring colony diameter after 4 days of incubation. Mycelial growth was maximal at 25 degrees C. The quantity and frequency pattern of mycelial growth of F. solani differ significantly at 15 and 25 degrees C, with maximal growth occurring at the highest water potential tested (-1.50 bars); and at 35 degrees C, with a maximal mycelial growth at -13.79 bars. The effect of water potential was independent of salt composition. The general growth pattern of F. solani showed declining growth at potentials below -41.79 bars. Fungal growth at 35 degrees C was always higher than that grow at 15 degrees C, of all the water potentials tested. Significant differences observed in the response of mycelia to water potential and temperature as main and interactive effects. The viability of cultures was increasingly inhibited as the water potential dropped, but some growth was still observed at -99.56 bars. These findings could indicate that marine strains of F. solani have a physiological mechanism that permits survival in environments with low water potential. The observed differences in viability and the magnitude of growth could indicate that the biological factors governing potential and actual growth are affected by osmotic potential in different ways.