Background

The filamentous fungus Magnaporthe oryzae can cause destructive rice blast and wheat blast diseases, which can also infect barley (Kohli et al., 2011; Dean et al., 2012). M. oryzae has been studied as a model to understand fungal-plant interactions (Yan and Talbot et al., 2016). This fungus initiates its infection by attaching the conidium to host surface, then the conidium germinates and forms a dome-shaped appressorium, by which it can penetrate into host cell for colonization (Wilson and Talbot, 2009). In host cells, the fungus colonizes as a biotrophic manner by forming bulbous and branched infection hyphae to interact with host defense system (Kankanala et al., 2007). M. oryzae sequentially invade living host cells and finally transformed into necrotrophic growth, during which the lesions appear and sporulation occurs. In order to study the fungal infection mechanism, or protein functions during infection, or plant defense reaction, it is required to observe cellular infection process of different strains in host cells. A rice leaf sheath method has been commonly used to observe the infection process (Koga et al., 2004), however, this method needs to waste a long time to prepare the rice leaf sheath, and the inoculation and sample preparation need a great deal of experience. Because barley is also the host of M. oryzae, and its leaf epidermis is easy for tearing, so we found that barley leaf epidermis method is an effective and simple method to observe the infection process of M. oryzae.