Abstract
By colchicine treatment of young seedlings autotetraploids of Avena hirtula (2x, AV=activating value=0.9), A. pilosa (2x, AV=0.5), A. longiglumis (2x, AV=1.7), and an amphiploid A. hirtula-pilosa (4x) were obtained. They were first crossed with some species of which AV had been known. Next, based on the crossing result AV of artificial polyploids was estimated by the method employed in the polar-nuclei activation hypothesis. That is, AV of 2.1 was assigned to A. hirtula (4x), 0.85 to A. pilosa (4x), 3.3 to A. longiglumis (4x) and 1.4 to amphiploid A. hirtula-pilosa (4x). It can be said that AV is nearly doubled if the chromosome number is duplicated, or nearly the sum of both parents′ in amphiploids. Artificial polyploids were surely different in their crossability from that of their original species but not in the crossability system.
