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 (Triti cum aestivum) known as tan spot. Brightfield and fluorescence microsco py were used to characterize the infection process and to identify the initial response mechanisms of susceptible and resistant wheat cultiv ars to a toxin-producing isolate (86-124) of the tan spot pathogen. An aniline blue fluorescent stain was developed to accurately identify f ungal infected host epidermal cells. Failure to penetrate epidermal ce ll walls or delayed infection was associated with the formation of pap illae (and occasionally haloes) at the infection site in susceptible a nd resistant hosts. Not all papillae were successful in preventing fun gal infection of the epidermal cells.