The changes of morphological properties of 13 Finnish oat varieties released between 1921 and 1988 and 13 Hankkija's breeding lines were evaluated in field trials. Twenty-two characteristics of oat stands were measured. The relationship between years of cultivar release and eharaeteristies of oats was studied by using the linear regression analyses and Spearman's rank eorrelation analyses.In both years of experiment there was a significant positive linear relationship between year of cultivar release and size and weight of the flag leaf, and mean panicle filling rate. The correlation was significant, but negative between year of release of cultivar and plant height. Also other relationships are discussed.

SUMMARYThe phenotypic stability of seven Finnish and Nordic oat cultivars and 12 breeding lines developed at the Hankkija Plant Breeding Institute, Finland, was studied using the Finlay–Wilkinson regression method, Eberhart–Russell stability analysis, principal component analysis (PCA) with biplot presentation, canonical variate analysis (CVA) and Procrustes analysis. Comparison of stability analyses was based on four dissimilar growing seasons. In addition to the measurement of phenotypic stability of grain yield, the performance of 12 morpho-physiological traits was evaluated, including maturity class and structure of canopy and plant stand.The different stability analyses examined produced uniform results and ranked the cultivars and breeding lines without major disagreements. Lines with exceptionally stable yield performance over the different growing seasons were identified. In general, there was an association of high yielding ability with poor stability. However, some cultivars deviated from this tendency and showed high grain yield production and average stability of yield performance.

Abstract. The effects of barley yellow dwarf virus on the development, grain yield and yield components of oat cultivar Veli and breeding lines Hankkija 78152 and 78033 were studied in two years. Cultivar differences to BYDV infection were best observed at a low infection level. Single tilleranalysis indicated close correlation between symptom severity and reduction in main yield components. Early infection caused greatest yield losses in all cultivars. BYDV strongly reduced both plant height and harvest index. Mild infection reduced the grain yield by 2-B %, but severe infection by 36-41°/o. The number of grains and panicle weight were strongly reduced, but the 1000-grain weight was only slightly affected after severe BYDVinfection. Implications of these results for disease control are discussed.

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