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Pfleeger, Thomas G., C.C. Mundt, and M.A. da Luz. 1999. Effects of wheat leaf rust on interactions between wheat and wild oats planted at various densities and proportions. Canadian Journal of Botany 77:1669-1683.

The importance of competition as a major influence on the composition and structure of plant communities has recently been questioned, because other types of interactions can cause significant compositional changes. The goal of this research was to broaden our understanding of disease as a process of structuring plant communities under a variety of competitive scenarios. Two cultivars of spring wheat (Triticum aestivum L., cv. Twin and cv. Penawawa) and wild oats Avena fatua L.) Were planted at three densities and at five proportions. One half of the experimental material was inoculated with uredospores of Puccinia recondita. Increasing the proportion of wheat or oats in mixtures led to significant increases in the amount of aboveground biomass and total seed weight for that species. The seed weight and aboveground biomass per culm or per planted seed decreased for wheat and wild oats as the proportion of wild oats increased in mixtures, indicting a competitive advantage for wild oats when grown with wheat. Wild oats generally did not respond significantly to the effect of leaf rust on wheat, while wheat performance declined. Lowered wheat performance in inoculated stands was the main reason for lower relative biomass ratios of wheat to wild oats. Puccinia recondita infections occurred late in the life cycle of wheat, thereby decreasing the potential impact on wild oats’ adults through competitive interactions.

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