CHROMOSOME NUMBER OF SACCHARUM SPONTANEUM L. COLLECTED FROM JAPAN

摘要

The authors proposed a method of improving glass slide preparation used in chromosome counts that calls for a hotplate treatment. Using this newly developed preparation, we surveyed the chromosome number of Saccharum spontaneum L. collected from different locations of the Southwest Islands, Japan. Fresh root tips were collected, pretreated in cold water for 24 hours, then fixed and stored. After enzyme digestion, chromosomes were spread over a slide in 2:1 v/v ethanol: acetic acid fixative, and then quickly dried on a hotplate at 45℃. After drying, slides were dipped in ethanol and fixative solutions. Cold water treatment effectively accumulated metaphase and pro-metaphase stages. Most countable chromosome spreads were round or oval shaped, with an average of 36 μm diameter. Ethanol and fixative treatment prevent chromosome loss during downstream preparation. Compared with the conventional air-dried treatment, high-quality chromosome spreads were obtained irrespective of environmental conditions. Mild heating by hotplate enhanced spreading due to a constant evaporation of the fixative. Treatment with ethanol and fixative solution enhanced chromosome attachment to the glass slide and removed cytoplasmic debris. Chromosome numbers of S. spontaneum were 2n = 96-112, with aneuploidy, and varied within some of the islands. Geographic distribution, chromosome number and evolution of S. spontaneum are discussed.