A Comparison of the Performance of Homogeneous and Heterogeneous Barley Populations1

Twenty‐three mixtures of barley (Hordeum vulgare L.) varieties were compared with their components for yielding ability and for yield stability at five locations in California over 2 years. The mixtures had a small advantage in yield over the average of the varieties but were inferior to their components in stability of yield. The yield advantage of mixtures decreased when environmental heterogeneity was reduced by excluding data from the most extreme location. The number or diversity of components in a mixture appeared unrelated to its yield. Certain F2 populations, included in the second year, were higher yielding but less stable than their parents. It was concluded that simple varietal mixtures have limited commercial possibilities and that special breeding programs may be necessary if favorable inter‐genotypic interactions are to be utilized.