Strain discrimination by fungal antagonists of Colletotrichum musae: implications for biocontrol of crown rot of banana

Single-strain biocontrol agents often look promising when tested against si ngle-strain pathogens. When confronted with a biodiverse field population, however, biocontrol is inconsistent. This study implies that biodiversity o f the crown rot pathogen Colletotrichum musae leads to strain discriminatio n by antagonists which results in variable biocontrol of the disease. Broad host-range mycoparasites of fungi of the crown rot disease complex of bana na (C. musae, Fusarium moniliforme and Botryodiplodia theobromae) which att acked at least two of the pathogen genera, exhibited significant difference s in aggression against different strains of C. musae, the main pathogen. A ntagonists acted via several different mechanisms, i.e. parasitism, antibio sis or competition, simultaneously. The relative importance of each mechani sm differed with the individual mycoparasites. Strain discrimination was co rrelated to differential susceptibility to one or more minor mechanism(s). When as many as four antagonists were combined into one inoculum, they comp lemented rather than antagonised each other. Biocontrol efficiency increase d with the number of antagonist strains combined. Therefore, strain mixture s should be sought to control the crown rot disease complex of banana.