Two cultivars of barley, Numar and Briggs, differing in their susceptibility to Rhynchosporium secalis, but without any known vertical genes for disease resistance, were grown in replicate plots and either inoculated with race 74 of R. secalis or sprayed with Benlate for disease control. Measurements included height, numbers of various plant parts, leaf area, dry weight of plant parts, yield components and grain yield. Analysis of the data indicated the more resistant variety Briggs, outyielded the susceptible variety Numar, and differed in other growth components. Calculation of leaf life span indicated this was a key difference between varieties with respect to disease resistance. Further testing on the relationship between leaf life span and disease resistance is necessary, but measurement of leaf life span may be a useful tool in screening breeding material for a background level of horizontal resistance, as well as leading to better understanding of a mechanism of disease resistance.
