Abstract
Hypo-pentaploid Triticale with four B chromosomes (2n=33+4B′s) derived from (Triticum durum×Secale cereale with 2B's) ×T. durum was cytologically studied, particularly on the normal chromosome component and on the behaviour of B chromosomes.
As a result of Giemsa staining for meiotic metaphase in pollen mother cells it was made clear that the normal chromosome component in the present Triticale consisted of 27 chromosomes of T. durum and 6 ones of S. cereale. The present Triticale showed a highly disturbed meiotic pattern. At MI the modal configuration of chromosomes was found in 12II+9I+2BII. At AI the unequal distribution in number and the many lagging chromosomes were observed, but the micronuclei at tetrad were a small number.
The number of B chromosomes in the present Triticale, BF1 plant, was twice as many as F1 parent. This indicates that in Triticale the nondisjunction of B chromosomes also takes place as well as in the original rye plant. The degree of multivalent formation between the B chromosomes was much lower in the present Triticale than in the original rye plants with 4B's. This indicates that the meiotic pairing of B chromosomes is disturbed by the change of genetic environment.
