Cytogenetic Studies in the Genus Potentilla L.

SUMMARY Cytogenetic studies involving eighteen species of Potentilla of the section Gymnocarpae were made to investigate their phylogenetic relationships and to see whether any correlation exists between morphology and crossing relationships. The chromosome numbers of Potentilla ambigens Greene (2n = 82) and P. montenegrina Pant, (2n = 28) were determined for the first time. New intraspecific chromosome races were observed in three species: P. pennsylvanica L. (2n = 42), P. astrisanguinea Lodd. (2n = 84) and P. grandiflora L. (2n = 42). Hybrids were obtained from only four of 628 crosses in 111 different combinations ( P. nepalensis Hook, × P. montenegrina Pant., P. astrisanguinea Lodd. × P. ambigens Greene, P. recta L. × P. cf. hirta L. and P. grandiflora L. × P. crantzii (Crantz) Beck.). The position of the crossing barrier in the unsuccessful crosses varied. Sometimes the pollen failed to germinate but in other cases well‐developed pollen tubes were observed. No definite correlation was found between the morphological similarity of species and their crossing ability. Meiotic studies on the hybrids indicated some chromosomal homologies between the genomes of P. recta and P. cf. hirta and between P. grandiflora and P. crantzii , but not between P. nepalensis and P. montenegrina .