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Meiotic behavior of B chromosomes of rye after transfer
to hexaploid wheat A. MUNTZING, H. JAWORSKA, and C. CARLIBOM Institute of Genetics, Lund, Sweden In the LINDSTROM strain of hexaploid wheat with B chromosomes from rye (Secale cereale), the B chromosomes are retained without difficulty in spite of the fact that much meiotic elimination occurs and that the strain is spontaneously self-fertilizing. A striking feature of the LINDSTROM strain is that the B chromosomes frequently undergo structural changes resulting in new types of B chromosomes : some of them are isochromosomes produced by mis-division of the centromere ; others must be products of deletions. The large iso-B chromosome has exactly the same appearance and tendency to undergo interarm pairing in the LINDSTROM Strain as in rye. In certain plants with one large iso-B chromosome and one standard B chromosome heterobivalents were formed between these chromosomes. Meiosis was studied in plants with 1, 2, 3, 4, and 6 B chromosomes of the standard type. Though a certain number of B bivalents are formed in the plants with two to six B chromosomes, meiotic pairing is on an average poor and the frequency of univalents is much higher than in the corresponding strain of rye. The reason for this difference must be an influence of the wheat chromosomes or the wheat cytoplasm on the rye chromosomes. Poor bivalent formation among the rye chromosomes, resulting from such an influence, does not only occur in the LINDSTROM strain but also in alien addition types with 42 wheat chromosomes and an additional pair of rye chromosomes as well as in strains of Triticale containing two complete genomes of rye. (Received Jan. 16, 1968) |