[The generation of H2O2 in wheat hypersensitive reaction induced by leaf rust fungus]

H2O2 burst in the defense responses of Wheat (Triticum aestivum L.) infected with compatible and incompatible leaf rust fungus races (Puccinia recondita f.sp. tritici) was investigated firstly. Cytofluorimetric analysis using the fluorescent probe DCFHDA scrutinized the generation of H2O2 in wheat primary leaves. The results indicated that H2O2 burst could be induced by either compatible or incompatible leaf rust fungus. However, the kinetics of H2O2 burst in incompatible interaction were biphasic, and the peak of phase II (20h after inoculation) was much higher than that of phase I (12h after inoculation), whereas, there only existed the weak and transient phase I H2O2 accumulation at 12h after inoculation in compatible interactions. In addition, pharmacological experiments were carried out. Antioxidants (AsA, DTT) and inhibitors of the mammalian neutrophil NADPH oxidase (DPI, imidazole) were separately injected into wheat primary leaves before inoculation to study their effects on hypersensitive reaction (HR) and H2O2 production in incompatible interaction. It was observed that treatments of wheat leaves with AsA, DTT, DPI or imidazole obviously suppressed the two peaks of intracellular H2O2 burst, whereas the second peak was inhibited much more. Moreover, the area of hypersensitively dead cells was decreased in the four treatments. These results suggested that NADPH oxidase may play an important role in H2O2 generation during wheat-leaf rust fungus interaction, and H2O2 burst may be involved in HR caused by leaf rust invading.