Chromosome characterization and physical mapping of 18S rDNA in Lilium longiflorum originated interspecific hybrids using combined genomic and fluorescent in situ hybridization

This study was aimed to differentiate parental genomes, examining intergenomic composition, and mapping mitotic metaphase chromosomes by localizing parental and 18S rDNA probes in seven interspecific hybrid progenies that originated from Lilium longiflorum. Since single method of in situ hybridization has been widely used in interspecific lily breeding, while in this study, flow cytometry was used in conjunction with genomic and fluorescent in situ hybridization to determine the genomic contribution of each parent to the interspecific progenies. A significant variation was observed in the DNA content, chromosome length, and 18S loci in F₁ as compared to the female and male parents. L. longiflorum showed nearly two times higher DNA content than the male parents and L. longiflorum × Asiatic progenies, but eight times higher than L. longiflorum × L. hansonii. Genomic in situ hybridization results revealed that both female and male parents contributed an equal number of chromosomes to their interspecific F₁ offspring. Fluorescent in situ hybridization mapping revealed that 18S rDNA had 8, 6 and 7 loci in L. longiflorum parents, i.e., White heaven, Bright tower, and White tower, respectively, whereas each Asiatic cultivar and L. hansonii used as male showed 8 and 12 loci respectively. Interspecific progenies showed 8 and 7 loci in LA, and 10–11 in LM hybrids. These cytogenetic results implied equal genetic and chromosomal contribution from both parents to their intergenomic progenies. Therefore, this combined cytogenetic method has the potential to be genome specific and time-saving approach in lily breeding that could determine the status of hybrids and their genomic origin while achieving physical mapping and detecting genes in different genomes.