Submitted to: New Phytologist
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/15/2005
Publication Date: 12/15/2005
Citation: Aver'Yanov, A., Lapikova, V.P., Pasechnik, T.D., Kuznetsov, V.V., Baker, C.J. 2005. Hydrogen peroxide at ultra-low concentrations affects early stages of fungus development. New Phytologist. Interpretive Summary: The overall goal of our work is to provide new insight into plant/pathogen interactions in order to develop new ways to improve disease resistance in crops. In this model system we are investigating spore germination by the rice blast fungus on rice leaves. Here we report that very low concentrations of hydrogen peroxide, much lower than previously considered, can inhibit spore germination in many fungal species. These low concentrations of hydrogen peroxide are currently below the detection limits of many studies. This new finding will have to be considered in reviewing previous studies that investigated the role of hydrogen peroxide in fungal spore germination. This work will benefit ARS and scientists by providing new knowledge about plant/pathogen interactions and help further investigations leading to improved crop disease resistance.
Technical Abstract: Hydrogen peroxide mediates some anti-infectional responses of plants. To evaluate its minimal fungitoxic amounts, it was applied to spores of the causal agents of cucurbit scab (Cladosporium cucumerinum) and rice blast (Magnaporthe grisea, formerly Pyricularia oryzae) over the broad concentration range (10-2 to 10-14 M). Spore germination and appressorium formation were examined. The dose-response dependence was multimodal for both fungi. The inhibition of spore germination was maximal at 10-2 M and practically disappeared at 10-5 - 10-6 M H2O2. However, weaker peroxide solutions had increased fungitoxicity. The inhibition of C. cucumerinum spore germination at 10-11 – 10-12 M was almost the same extent as at 10-2 M H2O2. For M. grisea, two maxima of germination inhibition near 10-7 M and 10-10 M H2O2 were found. Here, the toxicity was higher than at its millimolar concentration. M. grisea appressoria formation repeated the aforementioned pattern generally. Therefore, hydrogen peroxide can have an antifungal action at very low concentrations. Such small amounts of H2O2 might be sufficient for plant defense responses as well.