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Infection of Wheat by Cephalosporium gramineum as Influenced by Freezing of Roots. J. E. Bailey, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824, Present address: Department of Plant Pathology, North Carolina State University, Raleigh 27650; J. L. Lockwood(2), and M. V. Wiese(3). (2)(3)Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824; (3)Present address: Department of Plant and Soil Sciences, University of Idaho, Moscow 83843. Phytopathology 72:1324-1328. Accepted for publication 1 March 1982. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-1324.

Exudates collected from wheat roots that had been frozen and thawed increased spore germination, hyphal branching, and conidiogenesis of Cephalosporium gramineum more than did exudates from nonfrozen roots. Conidia subjected to soil fungistasis on the surface of nonsterilized soil germinated and penetrated wheat roots in the presence of exudate from roots that had been frozen. Hyphae grew throughout the cortical tissue. Plants with cut roots developed 62% infection following inoculation when roots were dipped into a suspension of conidia of C. gramineum and transplanted into soil. Only 03% infection developed in plants with cut root systems after they were transplanted into infested soil. Fourteen percent of the plants with intact root systems growing in infested soil became infected after exposure to 15 C, but none became infected when held at a low nonfreezing temperature (2 C). It was concluded that freeze stress may be an important factor affecting the predisposition of wheat plants to active penetration and infection by C. gramineum.