Scanning electron microscopy (SEM) was carried out to observe the infection dynamics of samples collected at different time points after inoculation. The samples were fixed in glutaraldehyde for 2 h and continuously dehydrated with alcohol and tert-butanol, followed by freeze-drying (Vacuum Device, VFD-30, Japan). These samples were coated with gold powder by spraying (Hitachi, MSP-2S, Japan) and observed using an SEM (Hitachi, TM-3030, Japan).
Furthermore, the leaf samples were analyzed by transmission electron microscopy (TEM) to determine the subcellular structural differences. The samples were fixed overnight in glutaraldehyde and dehydrated in acetone. These light microscopy and electron microscopy samples were processed as described by Redkar et al. (2015 (link)). Ultrathin sections were made using a Leica ultramicrotome (Leica, EM UC7, Germany) and observed under a Hitachi TEM (Hitachi, HT7700, Japan).