In semi-vivo antagonism of Acremoninum byssoides towards Plasmopara viticola

In previous laboratory tests the culture filtrates and the crude extracts obtained from Acremonium byssoides were shown to completely inhibit Plasmopara viticola sporangia germination. A study was thus undertaken in order to investigate on the possible inhibiting activity of the hyphomycete towards pathogenesis of the oomycete in grapevine. A. byssoides was cultivated on malt-extract agar (MEA) to obtain pure colonies and on maltextract broth (MEB) to obtain culture filtrate and crude extract. Healthy leaves of grapevine were put in Petri dishes containing sporangia suspended in: deionized sterile water, malt-extract broth, dimethylsulfoxide (DMSO), culture filtrate, crude extract and a suspension of A. byssoides germinated conidia. After 6 days from inoculations, the bioactivity of A. byssoides was evaluated on the basis of P. viticola evasion percentage. The results show that the higher percentage of pathogen evasion occurred in leaves inoculated with sporangia suspended in distilled water, in MEB and in DMSO; lower values of pathogen evasion were noted when leaves were treated with culture filtrate and crude extract; no evasion occurred in presence of A. byssoides germinated conidia, showing either antibiotic or hyperparasitic activity.