Neo-octaploids of Asplenium prolongatum Hook. (Aspleniaceae) occurred in Korea

Abstract

Asplenium L. is a sub-cosmopolitan genus of ferns comprising approximately 700 species. It includes various ploidy-leveled taxa, and, in particular, polyploid species occupy a higher proportion than diploid species within the genus. In addition, it is regarded as an essential process to confirm the cytotype of taxa because the ploidy level is sometimes used to identify a particular taxon in Asplenium. In the case of A. prolongatum, two cytotypes, tetraploid and hexaploid, have been reported in Japanese and Chinese populations. However, to date, there have been no attempts to confirm the ploidy of the Korean species. In the present study, we investigated the cytotype of Korean A. prolongatum using chromosome counting and genome size measurements, and we found that two cytotypes, hexaploid (2n = 6x = 216) and octaploid (2n = 8x = 288), were distributed in Jeju Island, Korea. To the best of our knowledge, this is the first report of a neo-cytotype of A. prolongatum. The hexaploids mostly had empty, shrunken sporangia, which is one of the traits observed in sterile hybrid ferns. From these results, it was concluded that A. prolongatum has three cytotypes: tetraploid, hexaploid, and octaploid.

Keywords

• Asplenium prolongatum
• Hexaploid
• Neocytotype
• Octaploid
• Spore fertility