Abstract
The relationship between severity of Xanthomonas streak and yield components of spring wheat [Triticum aestivum] was evaluated for plots and modified single tillers (MST). In the MST approach, tillers with similar disease severities were harvested and processed in bulk lots of 10 tillers. In three seasons, a 50% disease severity on the flag leaf resulted in an 8-13% loss in kernel weight; a 100% disease severity on the flag leaf resulted in a 13-34% loss. Disease onset was too late to affect the number of kernels per head. Protein concentration in the grain was positively correlated with disease severity in most years. The MST approach was deemed more efficient than single-tiller or plot methods for determining severity/loss relationships for this disease.