Elucidation of intergenomic recombination and chromosome translocation: meiotic evidence from interspecific hybrids of Lilium through GISH analysis

Intergenomic exchange has been found to be a normal phenomenon in sexual polyploids. In order to distinguish whether such exchanges are derived from intergenomic recombination or translocation, 13 genotypes of an interspecific hybrid, which were previously used as parents to generate sexual polyploids, were selected for a detailed meiosis analysis. In all genotypes under study, variable numbers of bivalents (0–12) resulting from homoeologous pairing were observed. But in two genotypes (006001-6 and 006001-13), a multivalent which was either a quadri- or a trivalent, as well as a bivalent involving two Asiatic chromosomes, was observed. Two Asiatic chromosomes in 006001-6 which were non-homologous were always found to be associated together, and formed trivalent or quadrivalent with chromosomes from homoeologous genome. This indicated that there was a duplication between these two Asiatic chromosomes. Such a duplication might have resulted from the segregation of a chromosomal translocation between two non-homologous chromosomes in the Asiatic parent ‘Connecticut King’ which was transmitted to the progeny (006001-6). With the exception of two genotypes, in 11 genotypes that formed variable frequencies of bivalents, the homoeologous chromosome pairing and chiasma formation were similar to that between homologous chromosomes. After from the analysis of anaphase I stages it was evident that the expected types of chiasma formation involving non-sister chromatids gave rise to two strand single, two strand double, three strand double, four strand double and multiple exchanges. Whereas these events resulted from locus specific homoeologous exchanges, the translocations resulted from an aberrant form of non-homologous chromosomal exchange of segments. Elucidation of such differences is only possible through the analysis of meiosis using GISH