Molecular cytogenetics in Lilium breeding

In horticulture, interspecific hybridization is one of the most important tools to achieve genetic variation; this is especially true when it comes to ornamental crops, where it is always necessary to introduce new traits, such as flower colour, petal shapes, stem size and strength, longevity, disease resistances and more. However, to maintain such traits in the progeny is necessary to introgress the genes of the alien species into the gene pool of the receptor species. To accomplish this, first sterility must be overcome, because, as a general rule, interspecific hybrids tend to be sterile. Mitotic polyploidization is a useful technique to come to such end, but the use of unreduced gametes is preferred because recombination occurs between the parental genomes and introgression might be achieved. Here it is described i) the production of interspecific, intersectional lily hybrids, obtained through the use special pollination techniques combined with ovary- and embryo-rescue techniques, in crosses of distantly related lily hybrids, cultivars and species from different taxonomical sections (L. longiflorum × Asiatic hybrids (LA), L. longiflorum × Oriental hybrids (LO), L. longiflorum × L. rubellum (LR), L. longiflorum × L. henryi (LH), L. henryi × L. candidum (HC), L. auratum × L. henryi (AuH), L. martagon × Asiatic hybrids (MA), Oriental hybrids × Asiatic hybrids (OA), Oriental hybrids × Trumpet hybrids (OT) and Oriental hybrids × L. pardalinum (OP)); ii) the use of molecular Genomic in situ Hybridization (GISH) to depict the mechanisms of 2n gamete formation and their use for the production of sexual polyploids; iii) the utilization of allotriploid BC1 progenies in introgression breeding and iv) the application of N₂O to induce the formation of unreduced gametes in sterile lily hybrids.