SCREENING FOR POTENTIAL ANTAGONISTS OF PSEUDOCERCOSPORELLA-HERPOTRICHOIDES, THE CAUSAL AGENT OF EYESPOT DISEASE OF CEREALS .2. FUNGI

The eyespot fungus Pseudocercosporella herpotrichoides survives on straw colonized during infection of a previous cereal crop, which then serves as an inoculum source for subsequent infection cycles. Tests were devised to identify fungal antagonists capable of competing with the pathogen on straw, and suppressing inoculum production and host infection. The 228 fungal isolates from wheat seedlings, plants or straw were screened for activity, along with 13 fungi and a commercial strain of Streptomyces griseoviridis which had proven biocontrol activity against other fungal pathogens. Potential antagonists were selected on the basis of inhibition or overgrowth of P. herpotrichoides on several contrasting nutrient media. Co-inoculation of straw with the pathogen and test antagonists reduced disease severity in pot trials using this straw as an inoculum source. When straw pre-inoculated with the pathogen was used, fewer antagonists proved effective in suppressing eyespot disease. However, one isolate, a Trichoderma sp., gave positive results both in vitro and in infection trials using different inoculation procedures, and may therefore be an effective antagonist of P. herpotrichoides during the saprophytic survival phase of the pathogen life cycle.