Cell death in wheat roots induced by the powdery mildew fungus Blumeria graminis f. sp. tritici

Inoculation of wheat (Triticum aestivum L. cv. Huamai 8) leaves with wheat powderly mildew fungus (Blumeria graminis f. sp. tritici) induced cell death in wheat adventitious roots, where no fungal structures were observed. The cytological and molecular characterization of this cell death was shown as following: cell nuclei were TUNEL positive labeled; genomic DNA was fragmented and showed DNA laddering; chromatin condensed and formed peripheral conglomeration in nuclei; and perinuclear spaces partly dilated. These results suggested that, without pathogen spread, the infection could induce systemic PCD in adventitious roots. Comparison with a leaf-cutting experiment (LC)enabled us to speculate that lack of assimilates was not the only reason for the systemic PCD in wheat roots in powdery mildew experiment and that such systemic PCD might be mediated by long-distance signals. In addition, reactive oxygen species (ROS) and Ca²⁺ were related to the systemic PCD.