Meiotic pairing in wheat–rye addition and substitution lines

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Abstract
Chromosome pairing was examined in wheat-rye addition and substitution lines using the C-banding technique. Both rye and wheat chromosomes affect each other''s homologous pairing. The strongest diminution of wheat pairing (measured as bound arms per cell) was produced by chromosome 5R of rye (7.5 and 7.2% in ''Chinese Spring''-''Imperial'' and ''Holdfast''-''King II'' addition lines, respectively). The weakest diminution of wheat pairing was produced by chromosome 3R in the ''Chinese Spring''-''Imperial'' addition line (1.1%). The diminution of rye chromosome pairing produced by wheat chromosomes ranges from 6.9 to 48.4% (''Chinese Spring''-''Imperial'' and ''Holdfast''-''King II'' addition lines, respectively). When put into a wheat background, the rye chromosomes suffer a worse fate than the wheat chromosomes. For example, chromsome 6R reduces the wheat complement pairing in the ''Holdfast''-''King II'' addition line by 3.8% but its own pairing is reduced by 41.4%. The decrease in pairing of both wheat and rye homologous chromosomes in addition and substitution lines is a complex process in which factors such as genes controlling meiotic pairing, constitutive heterochromatin, and cryptic wheat-rye interactions can play important roles.