Environmental and nutritional factors affecting the in vitro inhibition of the vegetative growth of Venturia inaequalis by five antagonistic fungi

Abstract

The environmental (temperature, pH, and light) and nutritional (carbon sources) factors that affect the inhibition of mycelial growth of Venturia inaequalis by five fungi (Aureobasidium sp. (P26A), unidentified fungus (P28A), Phoma sp. (P59A), Phoma sp. (P66A), and Ophiostoma sp. (P164A)) were evaluated. Cold temperatures slightly reduced the inhibition of V. inaequalis by Phoma sp. (P66A). A neutral pH increased the inhibition by the unidentified isolates and by a Phoma sp. (P66A). Continuous darkness enhanced the inhibition of the pathogen by the isolate Aureobasidium sp., and continuous light favored the inhibition by the Phoma sp. (P66A). The conidial germination of V. inaequalis was significantly reduced by all the isolates, and the inhibition was stronger closer to the fungal colony. Ophiostoma sp. inhibited 100% of the pathogen's growth regardless of temperature, pH, and light regime. Only the presence of peptone in the medium diminished the inhibition by 8%. Since Ophiostoma sp. strongly inhibited V. inaequalis (92–100% inhibition) and was not influenced by environmental and nutritional conditions, this fungal isolate could be considered in the development of a biocontrol agent against the apple scab pathogen. Key words: apple scab, biological control, environment, nutrition.