The Variations of the DNA Content in the Cell and Chromosome of Polyploid Forms of Mulberry (Morus L.)

We aimed at tracing the variations of the DNA content in mulberry polyploid forms with different chromosome sets. Both the extreme forms of 28 and 308 chromosomes and triploid and tetraploid forms which are intermediate in the chromosome number were chosen as the object of investigations. The local kind Dzhir-tut (2n=28) presented a diploid, naturally obtained Hanlar-tut (2n=42) and Tadzhanskaya- bessemyannaya (2n=42) were taken as triploids, naturally obtained Tegeran-tut (2n = 56) and experimentally obtained AzT-58-4 (2n = 56), AzT-58-10 (2n=56) were used as tetraploids. Har-tut (2n = 308) served as a hyperploid. The method consists in the spectrophotometric estimation of DNA content per unit of dry weight of leaves, calculation of cell number in standart sample of leaves by means of conting camera and recalculation of DNA content per one cell per haploid set of chromosome. In the cells of triploid and tetraploid forms of mulberry a normal I. 5-or 2-fold increase of the DNA content per cell is observed. In cells of Hyperploid forms with 308 chromosomes (2n = 308) the chromosome number increases 11 times as much as in diploid (2n = 28). Meanwhile the DNA content per cell increases only 4-fold so that its content per haploid set of chromosomes reduced three times.