Shozo Noda

Chromosomes of diploid and triploid forms found in the natural populations of tiger lily in Tsushima

The diploids (2n-24) ofLilium lancifolium were found together with triploids (2n=36) in the Tsushima islands, Nagasaki Pref., Japan. Four kinds of nucleolar chromosomes are common to nucleolar systems in mitoses of both forms. The gross morphology of the diploid form with numerous stem-bulbils closely resembles that of the triploid form.

Cytogenetics of the Scilla scilloides complex

There are two cytogenetically well differentiated genomes, A (x=8) and B (x=9), in the Scilla scilloides complex. The principal cytogenetic types form an aneuploidal series of chromosome numbers, i.e., AA (2n=16), BB (2n=18), ABB (2n=26), BBB (2n=27), AABB (2n=34), ABBB (2n=35), BBBB (2n=36), and AABBB (2n=43). These types are widespread in the Japanese islands, excepting AA which is confined to Korea. On the contrary diploid BB is not known from Korea. However, polyploids AABB and AABBB are known from both Japan and Korea.Plants of the complex do not grow in wild lands or montane regions, but in close relation to mans activities, e.g., in agricultural lands, on river banks, along roadways and railway lines, and in graveyards. Natural populations are, as a rule, a mixture of many different cytogenetic types.

Chiasma studies in structural hybrids IX. Crossing-over in pericentric inversion ofScilla scilloides

InScilla scilloides (Lindle) Druce, the heterozygotes for a pericentric inversion were found to be predominant in a small natural population consisting of cytogenetic type BB (2n=18). Pericentric inversion may include about half the length of the original subtelocentric chromosome, changing it to submetacentric. The 9II were always formed in these heterozygotes as well as in normal plants at MI in PMCs. A single chiasma was formed in the shorter one of two inverted segments divided by the kinetochore at MI, while one or two inversion chiasmata were observed in the longer segment. The AI separation was always regular. Since both arms of a normal chromosome and those of an inverted one were clearly distinguishable from one another at AI and AII, two kinds of crossover chromatids could be identified. Both sides of the single inversion chiasma always opened out reductionally. The frequency of bivalent without inversion chiasma agreed statistically with that of half-bivalent at AI or chromatid structure at AII, which resulted from non crossing-over within the inverted segment. Likewise, no statistical difference was found between the frequency of a single chiasma and that of a single crossing-over product in a longer inverted segment. These findings have clearly proved that the chiasma is a consequence of genetic crossing-over. The average proportion of good pollen grains in the inversion heterozygotes, 53.6%, amounted to about half that of normal plants, 97.7%.