VARIATIONS IN THE PATHOGENICITY OF FUSARIUM-OXSYPORUM F-SP VASINFECTUM IN RELATION TO THE SALINITY OF THE NUTRIENT MEDIUM

Since the Fusarium oxysporum f. sp. vasinfectum (FOV) chlamydospores a nd their germ tubes have been found to grow better in a saline medium (EC = 10 mmhos/cm), a study was undertaken to investigate whether the pathogenicity of this fungus is also affected by the salinity of the m edium on which it is cultured. FOV mycelium derived either from a non- saline medium (PDA, EC = 0.4 mmhos/cm) or from a saline-enriched mediu m (PDA + NaCl to EC = 10 mmhos/cm) was inoculated through wounds onto medium-resistant 'GSC 20' variety cotton seedlings (60 seedlings each) . Plant response was assessed through the following parameters: Number of necrotic stripes on the leaves, necrotic leaves, abscissed leaves, wilted plants. In all parameters, FOV was significantly more virulent (t = 0.01) when it had been cultured on a saline-enriched medium.