Analysis of Oriental × Trumpet (OT) Lilium hybrids by genomic in situ hybridization based on ploidy level

Genomic in situ hybridization (GISH) analysis was carried out to find out the chromosomal genomic composition in OT (Oriental × Trumpet) interspecific hybrids. In interspecific hybrids, most OT hybrids are triploid and developed by backcrossing with one of the parents, comprising a genome composition of OOT. To verify this statement, after cytoflow and chromosomal analysis, nine triploid (2n=3x=36), two tetraploid (2n=4x=48) and two diploid (2x=24) OT hybrids were screened out to analyze by GISH. GISH results depicted that tetraploid OT hybrid 'Stentor' showed 36 Oriental and 12 Trumpet lily chromosomes with two genomic recombinations. In spite of that, tetraploid 'Dolce and Gabanna' expressed equal parental genomic distribution, i.e., 24 maternal (Oriental) and 24 paternal (Trumpet) lily chromosomes. Therefore, two hybrids containing the same ploidy level showed variation in their genome composition. In the case of diploid hybrids, similar results were obtained with 12 chromosomes of each parental species. Furthermore, GISH analysis revealed extensive intergenomic recombination in the triploid hybrids. Triploid interspecific hybrid 'Empoli' genomic constituents showed 12 Trumpets and 24 Oriental lily chromosomes with two recombinant chromosomes. Similar results regarding chromosomal recombination were obtained in the 'Salamis' OT hybrid. GISH results indicated that there were more Oriental lily chromosomes than Trumpet lily chromosomes in OT hybrids. Therefore, it can be concluded that OT hybrids are developed by backcrossing of the Oriental parent, and in triploid hybrids, recombinant chromosomes can easily be screened out compared with diploid or tetraploid hybrids. Also, the GISH technique proved to be a key tool to verify the chromosomal arrangement in interspecific hybrids.