Detection of infection and host responses in susceptible and resistant wheat cultivars to a toxin-producing isolate of Pyrenophora tritici-repentis

Pyrenophora tritici-repentis causes the fungal disease of wheat (Triticum aestivum) known as tan spot. Brightfield and fluorescence microscopy were used to characterize the infection process and to identify the initial response mechanisms of susceptible and resistant wheat cultivars to a toxin-producing isolate (86-124) of the tan spot pathogen. An aniline blue fluorescent stain was developed to accurately identify fungal infected host epidermal cells. Failure to penetrate epidermal cell walls or delayed infection was associated with the formation of papillae (and occasionally haloes) at the infection site in susceptible and resistant hosts. Not all papillae were successful in preventing fungal infection of the epidermal cells.