Baking quality of wheat variety mixtures: Describing the mechanisms for mixture effects

The use of intra-crop diversity (e.g.: variety mixtures) in bread wheat cropping is getting popular in Europe, mostly for agronomic purposes. However, much less is known about the implications on baking quality. In this paper, we formalized and tested a framework based on two hypothetical mechanisms for mixture effects as a result of plant interactions within mixtures: (i) proportion shifts, relating to changes in grain weight proportion of the varieties at harvest and (ii) component alteration, relating to changes in the baking quality of the component varieties. To test this framework, we measured several baking quality indicators on twelve variety mixtures and their component varieties in pure stands. By recording varietal proportions at harvest, we could measure the relative importance of both mechanisms in explaining observed mixture effects. Our results showed that proportion shifts explained a large share of mixture effects on protein baking quality (Ze<acute accent>le<acute accent>ny sedimentation index and W baking strength) but failed to explain mixture effects on protein content in one year and Hagberg's falling number in both years. Our results also suggest component alteration on protein content resulting from altered nitrogen uptake in mixtures, and possibly on Hagberg's falling number resulting from lodging reduction in mixtures.