Stimulation of mycelial growth of pathogenic and seabed isolates of Fusarium oxysporum in presence of salts

Abstract

The mycelial growth of eleven Fusarium oxysporum strains, eight isolated from seabed soil of the South-eastern Mediterranean coast of Spain and three formae speciales from diseased plants were tested on potato-dextrose-agar adjusted to different osmotic pressures with either KCl or NaCl (-1.50 to -144.54 bar) at 10°C intervals ranging from 15 to 35°C. The extent of growth of F. oxysporum shows the same pattern for isolates from the seabeds that for isolates of Formae speciales. Maximal growth was observed at -13.79 bar of osmotic pressure at 25°C with an acute decrease at -41.79 bar and lower. At 35°C maximal growth was observed at -41.79 bar of osmotic pressure not only for seabeds isolates but also for pathogenic F. speciales isolates. These findings could indicate that F. oxysporum is well adapted to exist in moderate saline habitats. It does not seem that the pathogenicity of the isolates is a factor that determines the response to the salinity, but that behavior seems to be common to all the isolates studied and it could be speculated to be a specific behavior.