Analysis of introgression of the Tulipa fosteriana genome into Tulipa gesneriana using GISH and FISH

Southern hybridization and genomic in situ hybridization (GISH) have demonstrated that ‘Purissima’ (2n = 2x = 24) is an interspecific hybrid comprised of one genome of Tulipa (T.) gesneriana and one genome of T. fosteriana. Backcrossing T. gesneriana with ‘Purissima’ was partially successful. Simultaneous GISH and fluorescence in situ hybridization (FISH) distinguished chromosomes from both parent genomes, as well as recombinant chromosomes, in interspecific hybrids and their progeny. Chromosome recombination was observed in all cultivars except ‘Purissima’ and ‘Kouki’ (2n = 3x = 36). ‘Kouki’ (2n = 3x = 36) had two genomes of the T. gesneriana and a single genome of the T. fosteriana. The number of nonrecombinant T. fosteriana chromosomes in ‘Judith Leyster’ (2n = 4x = 48) and ‘Purissima’ progeny varied from two in ‘Hatsuzakura’ to six in ‘Kikomachi’ and ‘Momotaro’. The number and type of recombinant chromosomes also differed among cultivars. The total number of translocations ranged from one in ‘Kikomachi’ to six in ‘Hatsuzakura’. Each was a combination of a single T. fosteriana fragment and a single T. gesneriana fragment, indicating that they resulted from a single crossover event. Sequential GISH and FISH analysis with rDNA probes yielded chromosome-specific markers that were used to identify most of the chromosomes in ‘Purissima’ progeny. This is the first report of introgression of T. fosteriana chromatin into the T. gesneriana genome.