Cytogenetical Studies on Two Species of Morus

抄録

The mitotic number of several local varieties of M. indica is confirmed as 2n=28 and that of M. laevigata (2n=56) is reported as a tetraploid.
No meiotic difference was observable between the several varieties of M. indica. The following points were noted:-
1) There is extreme difference in size between 12 pairs called autosomes and 2 pairs called allosomes.
2) The four large chromosomes may join variously to form a) one quadrivalent, b) one trivalent and one univalent, or c) two bivalents.
3) The quadrivalent may separate equally or unequally at anaphase.
4) The allosomes show heteropycnosity to this extent that they may be visible, adhering to the nucleolus, at early prophase, when the other chromosomes are yet unstained.
5) It is contended from present observations that a simple “XY” me-chanism cannot exist in Morus as there are four large chromosomes in the complement.
6) Out of the remaining 24 chromosomes there may occasionally be formed one trivalent and a corresponding univalent.
7) Secondary grouping in both first and second metaphase adheres usually to the number seven.