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Occurrence and Distribution of Virulence in Puccinia coronata var. avenae in Europe, 1977-1980. J. Sebesta, Research Institute of Crop Production, 16106 Prague 6-Ruzyne, Czechoslovakia. D. E. Harder, Research Station, 195 Dafoe Rd., Winnipeg, Manitoba R3T 2M9, Canada. Plant Dis. 67:56-59. Accepted for publication 19 May 1982. Copyright 1983 Department of Agriculture, Government of Canada. DOI: 10.1094/PD-67-56.

Infection of oats (Avena sativa) by Puccinia coronata var. avenae is generally widespread over Europe, with the most severe infections occurring in the southern portion of the continent. From 1977 to 1980, crown rust isolates were obtained from various regions of Europe, and their virulence was determined on lines of A. sativa that contain known genes (Pc) for crown rust resistance. From 1977 to 1979, 12 lines were used as differentials; in 1980, 14 lines were used. In 19771979, 122 crown rust isolates from Austria, Czechoslovakia, Poland, Soviet Union/Lithuania, Soviet Union/northwestern, and Yugoslavia comprised 50 virulence combinations. In 1980, 176 isolates from Austria, Czechoslovakia, Federal Republic of Germany, Denmark, Italy, Poland, Portugal, and Switzerland comprised 75 virulence combinations. These results indicate the very high variability of virulence in the European isolates of P. coronata var. avenae. The distribution of virulence on the host resistance genes varied, depending on the region from which the isolates of P. coronata var. avenae were obtained. In general, the most ineffective genes in oats were Pc 35, 40, 45, 46, 47, and 54, whereas the most effective genes were Pc 39, 48, 50, and 55. The effectiveness of the remaining genes varied from poor to good, depending on the region. Limited data indicate that genes Pc 58 and 59 are highly effective. The usefulness of the Pc genes used in the study in relation to breeding oats for resistance in P. coronata var. avenae is discussed.