Reaction of spring barleys to common root rot and its effect on yield components.
The effects of the disease, caused primarily by Cochliobolus sativus, on yield components in 16 cultivars representative of 3 groups (2-row (Hannchen and Smyrna types), Coast and Manchuria) were studied at 2 Mont. sites in 1980. At Bozeman, autoclaved oat kernels colonized by C. sativus, added with seed, effected a mean disease rating among the cultivars of 42.8, compared to 30, when autoclaved uncolonized oat kernels were added. Despite the mean increase in disease severity of the inoculated plots, there was no significant difference in yield between inoculated and noninoculated plots. Later developed yield components, i.e. kernels/spike and kernel wt. compensated for the initial reduction in fertile tillers caused by the disease. Therefore, in populations of plants under disease pressure, compensating effects on yield components may allow for little or no overall yield reduction, particularly in cultivars that are not highly susceptible. The Hannchen cultivars were all intermediate in reaction at both locations. The Smyrna types were highly susceptible at Glasgow but intermediate at Bozeman. The 6-row, Manchuria and Coast groups were more diverse in their reaction at both locations. It appears that genetic relationships have more influence on a cultivar's disease rating than grouping based upon physiological characteristics.