Botrytis cinerea Infection Assay on Arabidopsis

Botrytis cinerea spores were diluted to 5 × 10⁴ spores per milliliter in Vogel buffer (Vogel, 1956 ) for drop inoculation assay or 2 × 10⁵ spores per milliliter in Vogel buffer for spray inoculation assay used for RT-qPCR analysis. The spores were pregerminated for 4 h before inoculations were carried out. For drop inoculations, 6 µL of spore suspension in Vogel buffer was carefully placed on the adaxial side (away from the midrib) of a fully expanded rosette leaf of 6–7 week-old Arabidopsis plants (at least 30 leaves were used from 10 independent plants). For spray inoculation, plants were sprayed until droplets began to run off the leaves (Mengiste et al., 2003 (link)). Inoculated plants were covered and grown under high humidity conditions for 3 or 4 days. Lesion diameters of drop-inoculated leaves were measured using a digital caliper and used to calculate lesion diameter. Spray-inoculated rosette leaves were harvested at 3 dpi. For fungal DNA quantification, fungal DNA was extracted using a plant/fungi DNA isolation kit (Norgen Biotek Corp, Thorold, Ontario, Canada) following the manufacturer’s protocol. The fungal β-ACTIN genomic DNA was quantified by qPCR (Ettenauer et al., 2014 (link)) using primers listed in Supplemental Table S1.