Chromosome numbers of experimental tetraploid hybrids and selfpollinated progenies within the<i>Achillea millefolium</i>complex (Compositae)

Abstract

SUMMARYNew crossing and selfing experiments within Achillea millefolium agg. (Compositae) succeeded with tetraploid individuals of A. ceretanica -4 x, A. collina, A. pratensis and F1 hybrids. Chromosome numbers of 105 out of 785 individuals including F1, BC, S1 offsprings and free pollinated F1 progenies were studied. Generally, plants were tetraploid, but occasionally aneuploids and a near-pentaploid plant originated from crossing and selfing experiments with A. ceretanica-4x and A. collina. The high degree of selfincompatibility within Achillea millefolium agg. is confirmed.