[Inbreeding depression and gene action in Secale cereale]

For the three characters "grain yield", "plant height" and "mean kernel weight" the inbreeding minimum was estimated in microperformance tests conducted with a plant density equivalent to field conditions. Values obtained were 24-34% for grain yield, 91-96% for plant height and 67-78% for mean kernel weight. None of the three characters showed significant deviation from linearity between the decline in performance and the increase of the inbreeding coefficient, i.e. there was no indication of epistatic gene action. For the character "grain yield" a high degree of dominance is indicated by high inbreeding depression linearily correlated with yield. This fact suggests the advisibility of breeding hybrid varieties. This issue is discussed in some detail.