RELATIONSHIPS BETWEEN COMMON ROOT-ROT, TILLERING, AND YIELD LOSS IN SPRING WHEAT AND BARLEY

Wheat grain yield decreased as symptoms of common root rot became more severe in plants with the same number of tillers. This trend was not as obvious in barley. However, as the season progressed, symptoms of c ommon root rot were most severe on barley plants with the fewest tille rs. In addition, the severity of the disease increased more rapidly on plants with the fewest tillers in wheat and barley. The major effect of the disease on yield reduction is that plants with more disease pro duce fewer tillers. A smaller effect is that grain yield per plant dec reases as disease increases in plants with the same number of tillers, which indicates that common root rot decreases the yield of individua l tillers.