Infection of field-grown winter wheat by Cephalosporium gramineum and the effect of soil pH

Field experiments were conducted at the Plant Disease Research Farm, Pullman, WA, from 1989 to 1993 to determine when Cephalosporium gramineum infects winter wheat, which plant parts are infected, and the effect of soil pH on infection (1991 to 1993). C. gramineum was isolated from winter wheat plants beginning in October each year before soil freezing occurred, confirming that soil freezing was not necessary for infection of winter wheat by the pathogen. C. gramineum was isolated frequently from seminal roots, crown roots, and stems, but infrequently from subcrown internodes. Since C. gramineum was rarely found in subcrown internodes, crown roots appeared to be the primary infection court. Likewise, C. gramineum was rarely isolated from roots with intact root tips or from root tissue near intact root tips, suggesting that the pathogen may have infected plants by colonizing senescent root cortical tissue, followed by penetration of the vascular system. In 2 years, C. gramineum was isolated from fewer crown roots of plants grown in soil with pH 6.7 to 7.2 than pH 4.7 to 5.9, but not until February or March. Increased infection of roots at low pH may have contributed to increased disease incidence; however, final disease incidence was greater for plants grown in the low pH soil in only 1 of the 2 years of this study.