2014 Volume 79 Issue 3 Pages 371-377
In this study, we confirmed the chromosome forms for M. montis-koyae (2n=18) and M. urticifolia (2n=18 and 2n=27). The chromosome count of 2n=27 is a new count for this species. These two counts reveal the basic chromosome number of x=9, which then becomes 2n=18. Thus, 2n=18 M. urticifolia is a diploid plant, and 2n=27 M. urticifolia is a triploid plant. The somatic chromosome complement was formulated as 2n=18=7m+9sm+2st. As such, the second longest chromosome pair is heteromorphic with long arms of different lengths. Notably, meiotic chromosomes at metaphase I showed nine bivalent chromosomes with terminal associations. In addition, pollen fertilities showed a range of 65.4–97.0%, while the karyotype was formulated as 2n=27=13m+14sm. Meiotic chromosomes at diakinesis and metaphase I had univalent, bivalent and trivalent chromosomes, and pollen fertilities showed a range of 2.3–29.0%. Thus, the triploid species is a segmental allotriploid plant. Both polyploid forms of M. urticifolia occurred widely in Japan.
