title: Effect of a rye B chromosome and its segments on homoeologous pairing in hybrids between common wheat and Aegilops variabilis.
abstract: Rye B chromosomes, which are supernumerary chromosomes dispensable for the host but increase in number by non-disjunction after meiosis, have been reported to affect meiotic homoeologous pairing in wheat-rye hybrids. The effect of a rye B chromosome (B) and its segments (B-9 and B-10) on homoeologous pairing was studied in hybrids between common wheat (2n=42) and Aegilops variabilis (2n=28), with reference to the Ph1 gene located on wheat chromosome 5B. The B-9 and B-10 chromosomes are derived from reciprocal translocations between a wheat and the B chromosomes, and the former had the B pericentromeric segment and the latter had the B distal segment. Both the B and B-9 chromosomes suppressed homoeologous pairing when chromosome 5B was absent. On the other hand, the B-9 and B-10 chromosomes promoted homoeologous pairing when 5B was present. On pairing suppression, B-9 had a greater effect in one dose than in two doses, and B-9 had a greater effect than B-10 had in one dose. These results suggested that the effect of the B chromosomes on homoeologous pairing was not confined to a specific region and that the intensity of the effect varied depending on the presence or absence of 5B and also on the segment and dose of the B chromosome. The mean chiasma frequency (10.23) in a hybrid (2n=36) possessing 5B and one B-9 was considerably higher than that (2.78) of a hybrid (2n=35) possessing 5B alone, and was comparable with that (14.09) of a hybrid (2n=34) lacking 5B. This fact suggested that the B chromosome or its segment can be used in introducing alien genes into wheat by inducing homoeologous pairing between wheat and alien chromosome.
authors.affiliation: Laboratory of Plant Genetics, Graduate School of Agriculture, Kyoto University, Kyoto, Japan.
authors.forename: Ryota
authors.initials: R
authors.lastname: Kousaka
authors.forename: Takashi R
authors.initials: TR
authors.lastname: Endo
mesh_terms: D002678:Chimera / Q000235:genetics*; D023902:Chromosome Pairing; D032461:Chromosomes, Plant / Q000235:genetics*; D017343:Genes, Plant; D008540:Meiosis; D008677:Metaphase; D011003:Ploidies; D006109:Poaceae / Q000235:genetics; D011995:Recombination, Genetic; D012434:Secale / Q000235:genetics*; D014908:Triticum / Q000166:cytology / Q000235:genetics*