Stripe Rust, Yield, and Plant Competition in Wheat Cultivar Mixtures

Mixtures of two, three, four, or five winter wheat (Triticum aestivum) cultivars and their component pure stands were either exposed to or protected from two stripe rust (Puccinia striiformis) races at three and two locations in 1986-1987 and 1987-1988, respectively. Disease severity and yield components per cultivar were determined for a subset of the mixtures and also for the pure stands. Disease severity in the mixtures compared to the mean of the components was reduced between 13 and 97%. Changes in disease severity could be separated into two effects. First, selection changed frequencies of the cultivars in the mixtures by up to 35% at harvest compared to the planted frequencies (...)