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

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 10ºC intervals ranging from 15 to 35ºC. Fungal growth was determined by measuring colony diameter after 4 days incubation. Mycelial growth was maximal at 25ºC. The quantity and frequency pattern of mycelial growth of F. solani differ significantly at 15 and 25ºC, with maximal occurring at the highest water potential tested (-1.50 bars); and at 35ºC, 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 35ºC was always higher than that growth at 15ºC, 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 growth could indicate that the biological factors governing potential and actual growth are affected by osmotic potential in different ways.