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Decline of Cephalosporium Stripe by Monoculture of Moderately Resistant Winter Wheat Cultivars. P. A. Shefelbine, Graduate research assistant, Department of Plant Pathology, Throckmorton Hall, Kansas State University, Manhattan 66506, Current address: Department of Botany, University of British Columbia, #3529-6270 University Boulevard, Vancouver, British Columbia, Canada V6T 2B1; W. W. Bockus, associate professor, Department of Plant Pathology, Throckmorton Hall, Kansas State University, Manhattan 66506. Phytopathology 79:1127-1131. Accepted for publication 6 June 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/Phyto-79-1127.

Winter wheat cultivars were grown in monoculture for 3 yr during a Cephalosporium stripe epidemic to determine if the rate-reducing phenomenon observed for several polycyclic diseases could be demonstrated for a monocyclic disease. Disease incidence, severity, and yield loss were monitored yearly. The susceptible cultivars Sturdy, Norkan, and Arkan were moderately diseased and exhibited moderate yield loss each year. Disease declined in years 2 and 3 in the moderately resistant cultivars Newton and Plainsman V, such that negligible disease was observed in the final year. Dodge sustained moderate stripe in the first year, but disease declined in the next 2 yr such that Dodge reacted similarly to Newton and Plainsman V in year 3. When disease incidence and severity were normalized for yearly differences in the environment by expression as a percentage of that observed for Sturdy, incidence dropped 1314% for Norkan and Arkan, 23% for Plainsman V, but 65 and 78% for Dodge and Newton, respectively. This study indicates that the rate-reducing phenomenon observed for polycyclic diseases exists for monocyclic diseases as well. Instead of disease declining during one season, disease declines over several seasons with monoculture of moderately resistant cultivars. Thus, high levels of resistance are not needed to control Cephalosporium stripe.

Additional keywords: Cephalosporium gramineum, soilborne disease.