INDUCTION OF HOMOEOLOGOUS PAIRING IN WHEAT BY GENES OF RYE SUPPRESSING CHROMOSOME 5B EFFECT

To test the effect of single rye chromosomes on the pairing of homoeologous wheat chromosomes, the seven wheat-rye addition lines of "Chinese Spring" and "Imperial" were crossed with Secale cereale L. and S. montanum L. In haploid triticale with 28 chromosomes (ABD R) no homoeologous pairing was induced. In the 29-chromosome hybrids, the two homologous rye chromosomes tended to form a rod bivalent indicating a suppressor effect of the wheat genome on chiasma formation between homologous rye chromosomes. Unequivocal evidence for homoeologous pairing of wheat chromosomes was found in several F1 plants. It is suggested that in the rye species Secale cereale and S. montanum the system which suppresses the activity of the Ph locus consists of more than two alleles which may act additively. They may be located on different chromosomes and may differ in number in the same genotype. Alleles effecting homoeologous pairing in wheat seem to be more frequent in S. montanum than in S. cereale. It is possible that in rye exceptionally strong alleles exist for homoeologous pairing.