Comparison of homoeologous recombination frequency between mitotic and meiotic polyploidization in BC₁ progeny of interspecific lily hybrids

Wide interspecific hybrids of lily generally show F₁-sterility. For overcoming this crossing barrier mitotic polyploidization (artificial chromosome doubling) or meiotic polyploidization through unreduced gametes can be applied. For introgression of the desirable characters from a donor into the recipient, homoeologous recombination is essential. 2x-gametes and 2n-gametes were compared with respect to the frequency of homoeologous recombination between parental chromosomes, in the F₁-hybrids as well as in BC ₁ progenies. GISH (genomic in situ hybridization) revealed that the LR and LA hybrids (2n=2x=24) composted of each genome set of parental chromosomes. These two types of F₁-hybrids (LR and LA) were used as a male parent to L. longiflorum and Asiatic hybrids. Since the LR-hybrid was absolute sterile, the chromosome number of this hybrid was doubled artificially, which recovered its fertility. GISH results revealed that the BC₁ individuals (2n=3x=36), LLR and ALA, differed on homoeologous recombination frequency. Recombinant chromosomes were not be demonstrated in the mitotic chromosome complements of the LLR-hybrids. This lack of exchange between homoeologous chromosomes caused by complete preferential pairing of the L-L and R-R chromosomes during the meiosis of F₁-hybrid (LLRR). On the contrary, ALA-hybrids derived from functioning of 2n-gamete of LA hybrids showed a range of homoeologous recombinations between L and A chromosomes. Homoeologous recombinations were obtained by homoeologous pairing between L and A chromosomes during meiosis. As a conclusion, 2n-gametes producing F ₁ interspecific hybrids have a high potential to introgress certain characteristics selectively.