Physical mapping of 45S rDNA loci in Lilium OT hybrids and interspecific hybrids with Lilium regale

Crossing between Lilium OT (Oriental x Trumpet) cultivars and L regale could provide an accessible way to develop lily cultivars with both horticultural traits and stress resistance. Physical mapping of 45S ribosomal DNA (rDNA) loci by fluorescence in situ hybridization (FISH) can help understand genetic relationships and chromosome inheritance in lily breeding. In this study, hybrid progeny were obtained from the combinations of 'Conca d'Or' x L. regale and 'Saltarello' x L. regale, confirming the fertility of OT cultivars as female parents in crosses with L. regale. 'Saltarello' x L. regale had the highest embryo rate (8.96), indicating cross-compatibility between 'Saltarello' and L. regale. Based on the results of crossing and FISH, the genetic relationship between OT cultivars and L. regale was further investigated. 'Saltarello' possessed twelve 45S rDNA signal loci, of which eight were similar to those of L. regale, on chromosomes 1, 2 and 5, confirming the closest genetic relationship with L. regale, 'Conca d'Or' with five similar sigals second and 'Manissa' with three similar sigals farthest. The 45S rDNA loci in hybrids of 'Saltarello' x L. regale were located on chromosomes 1 through 6 and varied in number from 7 to 13. These hybrids included both euploids and aneuploids, demonstrating that allotriploid Lilium OT hybrids can produce viable gametes with euploid and aneuploid chromosome numbers. Thus, it should be possible to select new cultivars from interspecific hybrids of OT hybrids x L regale.