Dimethomorph activity and its effect on morphology in different oomycete species of economic and veterinary interest

Several oomycete species are pathogenic to plants or animals, including humans, and cause economic and environmental damage, nevertheless no effective molecules against these pathogens are available. Dimethomorph (DMM), is a fungicide with high activity against plant pathogenic oomycetes used to control downy mildew. The current study aims at developing a transversal approach and to do that, we evaluated: 1) the effect of two concentrations of DMM on in vitro mycelial growth on Saprolegnia and Pythium isolated from fish and aquatic environment; 2) the effect of DMM on hyphal morphology of S. parasitica and on the sporangia and hyphae of a P. viticola strain using Scanning Electron Microscopy. Results indicated that radial growth of Saprolegnia species was reduced at 50 and 100 mg/L of DMM after 24h of incubation. For P. viticola at 50 mg/L sporangia are rarely present with respect to the control and in 100 mg/L are not present at all. Moreover, a SEM protocol was developed, and allowed to observe how the fungicide induced changes at the morphological level in both oomycete species.