Corresponding test kits

Total flavonoid content was measured as described previously by Jia [83 (link)]. For chlorophyll fluorescence measurements, the images were obtained by IMAGING-PAM chlorophyll fluorometer (Walz, Effeltrich, Germany), and the maximum quantum efficiency of photosystem II (Fv/Fm) was measured with Imaging WinGegE software [84 (link)]. H₂O₂ and O₂⁻ were stained with DAB (Solarbio, Beijing, China) and NBT (Beijing Biodee Biotechnology, Beijing, China). The programmed cell death was detected by 0.4% trypan blue solution (MYM Biological Technology Company Limited, Chicago, IL, USA). The H₂O₂ and O₂⁻ content was measured as described previously by Liu and Elstner [85 (link),86 (link)]. EL was measured as described previously by Ben-Amor [87 (link)]. MDA, proline, SOD, POD, and CAT activity were detected using corresponding test kits (Nanjing Jiancheng Bioengineering Institute, Nanjing, China) [88 (link)].

Enzyme activity and antioxidant content of kiwifruit were determined according to Huang et al. [21 (link)] with little modification. Kiwifruits were treated sequentially with strain 37 (SDW as control) and B. dothidea, as described in Section 2.2. Healthy tissues surrounding the wounds (within 1.5 cm) were taken and mixed every day until 5 dpi. Samples were frozen immediately in liquid nitrogen and kept in the ultra-cold freezer at −80 °C. Each treatment contained three replicates and each replicate consisted of 6 kiwifruit. Defense enzymes activity of superoxide dismutase (SOD), catalase (CAT), phenylalanine ammonia-lyase (PAL), glutathione (GSH), and total phenol content were determined using corresponding test kits (Nanjing Jiancheng, China). Flavonoids content and cell wall degrading enzyme activity of β-galactosidase (β-Gal) and polygalacturonase (PG) were assessed by enzyme-linked immunosorbent assay (Elisa) kits (Feiya Biotechnology, Yancheng, China).