Segregation in the pollen of F₂ rye (Secale cereale) plants for induction of homoeologous chromosome pairing in hybrids with wheat (Triticum aestivum)

Abstract

An attempt was made to determine the inheritance of the rye genes which induce high chiasma frequency in hybrids with wheat and to study if the ability of rye to induce partial amphiploidy in hybrids with wheat was heritable. Five to eight F₂ pollen plants were derived from seeds taken from each of three F₁ plants that had given high chiasma frequency in hybrids with 'Chinese Spring' wheat in earlier studies. Similarly, six to seven F₂ pollen plants were derived from each of three F₁ plants that had given partial amphiploids in hybrids with 'Chinese Spring' wheat in earlier studies. Chiasma frequency was studied in 127 hybrids with 'Chinese Spring' wheat. In the present study, significant differences in chiasma frequency were observed (i) among the 38 families represented by 127 plants, and (ii) between two groups of three sets each, one known for inducing high pairing and the other known for inducing partial amphiploidy associated with low pairing in wheat × F₁ rye plants. Significant variation was also observed between families within sets (each originated from one F₁ rye plant) suggesting that F₂ rye plants derived from the same F₁ plants also differed genetically for inducing heterogenetic (homoeologous) pairing in wheat × rye hybrids. One of the six sets particularly showed significantly higher pairing with a mean of 2.13 per cell (individual hybrids gave a chiasma frequency as high as a mean of 6.07 per cell) as against a range of 0.96 to 1.18 in the remaining five sets, suggesting accumulation of genes in F₂ rye plants for inducing pairing in wheat × rye hybrids. It is expected that by intermating the segregating rye plants, it should be possible to accumulate genes and eventually to isolate homozygous lines inducing high pairing in hybrids with wheat. Contrary to expectation, no partial amphiploids were obtained in a study of 127 wheat × F₂ rye hybrids, although three of the six F₁ rye plants had earlier given partial amphiploids in wheat × F₁ rye hybrids.