REACTION OF SPRING BARLEYS TO COMMON ROOT ROT AND ITS EFFECT ON YIELD COMPONENTS

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Abstract
The effects of common root rot (CRR), caused primarily by Cochliobolus sativus, on yield components in 16 barley cultivars representative of three groups—two-row (Hannchen and Smyrna types), Coast, and Manchuria—were studied at Bozeman and Glasgow, Mont, in 1980. At Bozeman, autoclaved oat kernels colonized by Cochliobolus sativus added with seed, effected a mean disease rating (DR) among the cultivars of 42.8, compared to 30.3, when autoclaved uncolonized oat kernels were added. In spite of 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 per spike and kernel weight, compensated for the initial reduction in fertile tillers caused by CRR. Therefore, in population of plants under disease pressure from CRR, compensating effects on yield components may allow for little or no overall yield reduction, particularly in cultivars that are not highly susceptible to CRR. The two-row, Hannchen-type cultivars were all intermediate in DR at both locations. The two-row, Smyrna-type cultivars were high in susceptibility at Glasgow but intermediate in reaction to CRR at Bozeman. The six-row, Manchuria-Coast groups of cultivars were more diverse in their reaction to CRR at both locations. It appears that genetic relationships have more influence on a cultivar’s disease rating to CRR than has grouping based upon physiological characteristics.Key words: Barley groups, Cochliobolus sativus, yield components