Prediction of grain yield of spring barley varieties by disease and growth characteristics from VCU testing.

Fifty spring barley varieties grown under organic as well as conventional growing conditions in experimental fields in four combinations of year and site were studied. The yield varied greatly within and between environments (years and sites) and systems. Furthermore, the variation among varieties was substantial and differed among different environments and systems. Associations between observed grain yield of these varieties and disease and growth characteristics assessed in the official conventional variety testing were compared between the organic and the conventional system. Using factorial regression analysis, the best model was found for predicting the observed grain yield each year from these characteristics in the previous year. In this model, the residual variance component for varieties was lower for observations from the conventional growing system than from the organic growing system, implying that the VCU-characteristics better predicted the results from conventional growing system. The implications for organic variety testing are discussed.