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Ecology and Epidemiology

Effects of Two-Component Wheat Cultivar Mixtures on Stripe Rust Severity. Shamsul I. Akanda, Department of Botany and Plant Pathology, Oregon State University, 2082 Cordley Hall, Corvallis 97331-2902; Christopher C. Mundt, Department of Botany and Plant Pathology, Oregon State University, 2082 Cordley Hall, Corvallis 97331-2902. Phytopathology 86:347-353. Accepted for publication 20 December 1995. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/Phyto-86-347.

Three two-component wheat (Triticum aestivum) cultivar mixtures, along with their pure stands, were grown at five ratios in three experiments. Each cultivar was susceptible to either one or two of three Puccinia striiformis races inoculated into the plots. Chaff color differences served as markers to distinguish the cultivars in mixture, so that disease could be calculated on a per-cultivar basis. Stripe rust severity on individual cultivars increased linearly with the frequency of that cultivar in mixture, with 16 of 18 possible regressions having significantly (P ≤ 0.05) positive linear slopes. One cultivar had significantly different levels of rust when mixed with different companion cultivars, suggesting that plant-plant interactions affected susceptibility of that cultivar to rust. In contrast to an earlier study, changes in frequencies of mixture components from planting to harvest had little influence on stripe rust severity. Mixtures with equivalent proportions of cultivars generally provided the highest level of disease control.