Breeding strategies for a spring barley pea mixed cropping system

Introduction and methods Crop mixtures of cereals and legumes have received recent attention in the scope of climate change and local protein supply. Cereal-legume mixtures are known to increase yield and yield stability compared with pure crops. Thus dedicated breeding strategies for mixed cropping might become necessary. As a model crop, we compared 32 current European spring pea (Pisum sativum L.) and 8 current spring barley (Hordeum vulgare L.) cultivars for their yield performance in mixed and pure stands, with pea as the focal species. Trials were done as an incomplete factorial design (Fig. 1) at two locations in Switzerland with two replications (Fig. 2). We calculated variance components for the general and specific mixing ability (GMA and SMA, respectively), in accordance to general and specific combining ability in hybrid breeding. GMA can further be partitioned in Producer (Pr) and Associate (As) effects, with Prp being the effect of a pea variety on its component pea yield in the mixture and Asp the pea variety effect on the companion barley yield.