Verticillium wilt and Fusarium wilt, vascular diseases caused by the soil-borne fungal pathogens Verticillium dahliae and Fusarium oxysporumf.sp vasinfectum, respectively, are among the most important diseases of cotton (Gossypium spp. ), with the potential to cost the cotton industry millions of dollars in lost production. These fungi colonise the plant roots and penetrate the vascular tissues, where they proliferate in the vascular system and are eventually distributed throughout the plant. Plants infected with either Verticillium Fusarium display similar symptoms of chlorosis and necrosis of leaves, defoliation, stunting or plant death. Cross-sections of the stern reveal a brown or black centre which is due to the formation of meIanised products in the infected vascular system. However, chlorosis in Fusarium wilt tends to be in patches and vascular browning is more pronounced than in Verticillium wilt. In general, the symptoms of Fusarium wilt are much more severe and result in greater crop losses (Bell, 1992a and 1992b).