A perspective for the use of synthetic analogs of the natural peptaibol trichogin GA IV as biopesticides

Trichoderma spp. represent a rich source of bioactive molecules for controlling plant pathogens. As bioactive molecules, antimicrobial peptides (AMPs) are gaining interest as candidates for new eco-friendly plant protection products. Peptaibols are a peculiar class of AMPs with a well-defined helical structure but poor water solubility, which hampers their use in crop protection. Based on these premises, we used a biorational approach to synthesize peptide analogs of the natural peptaibol trichogin GA IV with Gly‐to‐Lys substitutions to enhance water solubility and antimicrobial activity. We obtained several water-soluble analogs with in vitro fungicidal and bactericidal activity. Some of these analogs completely inhibited the growth of the fungus Botrytis cinerea and the sporulation of the oomycete Plasmopara viticola at low micromolar concentrations. The peptide analogs also exerted bactericidal activity against the bacteria Xanthomonas campestris pv. campestris (Xcc), Pseudomonas syringae pv. tomato and P. syringae pv. actinidiae. In growth chamber experiments, the most effective peptides protected grapevine from P. viticola and B. cinerea and cauliflower from Xcc without phytotoxic effects. The microscopic analysis showed different alterations of the cell membrane and the cytoplasm depending on the examined plant pathogen. Finally, in a two-year field trial, one selected peptide resulted as effective as a cupric fungicide in protecting the vineyard from downy mildew.