Verticillium dahliae is a highly destructive fungal pathogen that causes an annual global product loss in cotton of 20%. Currently there are no effective treatments for verticillium wilt, but bioinoculants might provide an environmentally friendly solution. This project aimed to: develop methods to study the interactions between the cotton plant Gossypium hirsutella, the pathogen V. dahliae and a rhizopheric competent fungal symbiont, Beauveria bassiana. To quantify root colonisation by the pathogen and/or symbiont in single or multiple inoculations, and to identify patterns in peptides secreted by the plant, pathogen and symbiont during single or multiple inoculations. Soil was replaced by vermiculite and the plants were cultivated using Hoagland’s nutrient solution allowing complete control over their nutrient availability and uptake. This study found that there was no significant difference in the susceptibility of two cotton cultivars Sicot F-1 and Siokra 1-4. Results indicated that pre-infection with B. bassiana cause no interference with V. dahliae’s ability to colonises and infect the plants. B, bassiana did however supress the infection of a contaminating unidentified Aspergillus. Post-infection of B. bassiana did have a significant effect on the colony forming units of V. dahliae when it was introduced as a pre-infection, this interaction also occurred when the fungi’s roles were reversed. A significant difference in peptide secretion profiles was observed when comparing UV chromatographs from different treatments.