FIGURE 5.

Effects of pure volatile organic compounds (VOCs) on callose deposition and downy mildew development. Grapevine leaf disks were treated with water (control) or with 10 mg L⁻¹ in air volume of 2‐pentylfuran or 6‐pentyl‐2H‐pyran‐2‐one. Callose deposition and Plasmopara viticola development were monitored before inoculation (0 dpi, A–D), at one (E–H), two (I–L) and six (M–T) days post inoculation (dpi) using aniline blue staining. As control of callose deposition, leaf disks were sprayed with Trichoderma harzianum T39 conidia and inoculated with P. viticola (Palmieri et al., 2012). The experiment was carried out twice and a representative leaf disk of 10 is shown for each treatment. Abbreviations: Cal, callose; Sv, substomatal P. viticola vesicle; St, stomata guard cells