3.2 Accumulation of H2O2 and O2- in melon leaves after GSB infection
Accumulation of H2O2 and O2- in the leaves of PI511890 and Payzawat was determined using DAB and NBT staining methods at 12, 24, 36, and 48 hpi, respectively. The results of DAB staining showed that H2O2 accumulation in infected leaves was higher than that in the control for both Payzawat and PI511890, indicating that GSB promotes H2O2accumulation (Figure 1B). Compared with the control, significantly higher accumulation of H2O2 was observed in Payzawat after 24 hpi (Figure 1D). However, significantly higher accumulation of H2O2 was only observed at 24 hpi in infected leaves of PI511890 compared with the control. Moreover, H2O2 accumulation in infected leaves of Payzawat was consistently higher than that of PI511890. Similar accumulation patterns of O2- were also observed in the leaves of Payzawat and PI511890, indicating that GSB also induces the accumulation of O2- (Figure 1C). Additionally, O2- accumulation in infected leaves of Payzawat was significantly higher than that of PI511890 at 24 hpi (Figure 1E). The lower accumulation of H2O2 and O2- in PI511890 suggested that reactive oxygen homeostasis is possibly involved in the resistance to GSB.