Sexuality, apomixis and polyploidy; Potentilla argentea as a critical example

Sammanfattning: Finding a diploid facultative apomictic plant species would give a great opportunity to solve problems concerning the existence and persistence of sexuality and also, it would be a possible source to get a transferable apomictic gene from. The putative diploid facultative apomict Potentilla argentea from southern Sweden was investigated with RAPD, isozymes and flow cytometry. Its mode of reproduction in nature was found to be sexual, primarly by self-fertilization but outcrossing occured at a measurable rate. No traces of apomixis were found. All offspring from artificial crosses in greenhouse environments, both with diploid and hexaploid pollen donors, were sexually derived. Also in this experiments no traces of apomixis could be found. Two tetraploid hybrids were obtained in crosses between diploid and hexaploid P. argentea. Diploid and hexaploid Potentilla argentea L (s.l.) are found in extensive sympatry in southern Sweden. The hexaploid form is an allohexaploid. Due to similarities in morphology and isozymes we suggested the diploid form to be one of the parent species. We found any evidence of multipel origin of the hexaploid form. Instead the many clones found in the investigation area is suggested to be a result of apomictic reproduction intervined by occasional outcrossing. All offspring in artificial crosses in greenhouse, except one with 9x, were apomicticly reproduced.