Effect of water activity and temperature on competing abilities of Penicillium oxalicum against Fusarium oxysporum

The in vitro effect of water activity (0.995, 0.98, 0.95, 0.90 and 0.85) and temperature (25 and 15 degrees C) on competing abilities of the biocontrol agent Penicillium oxalicum against Fusarium oxysporum fsp. lycopersici, a tomato pathogen, and Fusarium oxysporum fsp. gladioli, a gladiolus pathogen, was evaluated. The aim of this study was to assess the suitability of P. oxalicum to be applied as a biocontrol agent against these phytopathogenic fungi. Plates were inoculated in two points with P. oxalicum and one of the Fusarium species. Two different approaches were taken into account: the growth rate of each isolate and the Dominance Index (ID). P. oxalicum showed higher growth rates under most of the conditions tested except for 0.995 aw at both temperatures and at 0.98 and 15 degrees C. Similarly, P. oxalicum was dominating at 25 degrees C and < or = 0.95 aw, and at 15 degrees C and < or = 0.90 aw, while under the other conditions studied, mutual inhibition situations were found. This indicates a high ability of this species to successfully compete over a wide range of conditions and consequently the potential of P. oxalicum as a biocontrol agent against these Fusarium species.