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Disease control in variety mixtures is not directly linked with yield benefit.

Adrian Newton: James Hutton Institute

<div>The reduction in disease in cereal variety mixtures is normally correlated with the number of component varieties, as is the yield benefit. However, the link between disease and yield is indirect as the effect of disease is only one of many interactions between mixture components that ultimately affect grain and straw yield. Use of fungicide treatments to compare diseased and non-diseased plots can be misleading as varieties interactions are still influenced by microbial challenge. Furthermore, nutrient availability and thereby source-sink interactions affect both disease development and variety interactions. We show that designing mixtures for enhanced yield involves optimising multiple competing and facilitating interactions and that the disease component should be optimised within this complex framework.</div>