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Infection of Winter Wheat by a β-Glucuronidase-Transformed Isolate of Cephalosporium gramineum

March 2001 , Volume 91 , Number  3
Pages  232 - 239

G. W. Douhan and T. D. Murray

Department of Plant Pathology, Washington State University, Pullman 99164

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Accepted for publication 20 November 2000.

Field-grown winter wheat was inoculated with a β-glucuronidase-transformed isolate of Cephalosporium gramineum in two field seasons to elucidate the mode of infection in resistant and susceptible cultivars. Colonization of viable root epidermis and cortical cells occurred as soon as 15 days postinoculation and the pathogen was found in the vascular tissues by 20 days postinoculation, well before freezing soil temperatures occurred. Penetration occurred directly through the root epidermis and through wounds adjacent to emerging secondary roots. The pathogen also penetrated through root cap cells and colonized meristematic tissues near root tips to gain access to the vascular system. Lower stem base colonization was observed where the pathogen penetrated directly through the epidermis, wounds, or senescent tissues. Appressorium-like structures, which appeared to aid penetration of cell walls, were often found within cells of both roots and stems after initial colonization. The mechanisms of resistance were not apparent, but less colonization occurred in resistant than in susceptible cultivars.

© 2001 The American Phytopathological Society