Septoria leaf blotch causes economic yield losses in wheat worldwide. Research on the impact of septoria leaf blotch on grain quality, however, has been limited to its effect on test weight. The objectives of this study were to determine the effect of septoria leaf blotch severity on soft red winter wheat quality in cultivars with varying levels of resistance and to assess the impact of disease pressure on selection for improved quality in breeding programs. 

Twelve cultivars expressing a range of genetic resistance were grown in a split-plot design with four replicates in two Missouri environments. Cultivars were considered main plots. Five experimental subplot treatments, including a non-inoculated unprotected control and plots with fungicide protection as well as plots inoculated at tillering, jointing, and flag leaf, were used to establish a range of septoria leaf blotch severity. Increased disease pressure resulted in linear reductions in test weight (r = 0.97**), milling quality (r = 0.98**), adjusted flour yield (r = 0.97**), and a linear increase in water absorption in the flour (r = 0.95**). 

Increased disease severity also resulted in an increase in flour protein and a decrease in baking quality, however, the linear correlation coefficients were non-significant. The role of resistance genes for maintaining quality was important for milling quality but was negligible for baking quality. Cultivar by treatment interactions were due primarily to changes in magnitude and not in cultivar rank, which suggested that selection for milling and baking quality would be effective even when septoria leaf blotch disease pressure is high.