The Effect of Inoculum Pressure, Germplasm Selection and Environment on Spring Barley Cultivar Mixtures Efficacy

A range of mixtures including one set made from cultivars grown in the UK and one from cultivars grown in Poland, were included, along with their component cultivars, in nine trials at Scottish Crop Research Institute, Dundee, UK or at the Experimental Plant Breeding Station of the IHAR, Baków near Kluczbork, Poland, over five seasons. The effects of inoculum pressure, plot size, fertiliser level and germplasm on mixture efficacy were investigated. In the four trials where inoculum pressure was controlled, mixtures reduced infection more at lower inoculum pressures, but this did not translate into yield benefit. Smaller plots increased mildew in monocultures but not mixtures. Fertiliser levels increased mildew levels but did not affect mixture efficacy. There were large differences between both Polish and UK germplasm, and between Polish and UK trial sites, but the performance of the mixtures compared with their respective monoculture components was similar within both germplasm groups and trial sites. Mixtures reduced lodging and affected plant height and heading date. The advantages of mixtures for improving yield, reducing fungicide applications and improving agronomic characteristics was demonstrated and there seems to be great potential for their further improvement and exploitation. This revised version was published online in August 2006 with corrections to the Cover Date.