An Analysis Of The Ploidy Levels And The Karyotypes Of Tulipa Cultivars

Tulip is perennial bulb flowers belong to Tulipa genus of the Liliaceae family,which is the most significant cut flowers in the world.Compared with other popular flowers,Tulipa has more difficult problems for breeding.Investigation of ploidy levels and karyotypes would be useful to guide the breeding new tulip cultivar.This paper collected 10 tulipa cultivars,investigated their pollen germination rate,and used the technique of conventional chromosome preparation and fluorescence in situ hybridization with rDNA as probe to analyse their ploidy levels and karyotypes.The mainl results are as follows:1.Among the ten Tulipa cultivars,seven of them,‘Spring Green',‘Daydream',‘Ile de France',‘Candy Prince',‘White Prince',‘Flaming Flag',‘Rio Carnival',are diploid(2n=2x=24),three cultivars,‘Negrita',‘Queen of Orange',‘Red Impression',are triploid(2n=3x=36).Because wild species are generally diploid,triploid might be a major trend of Tulipa breeding work.2.Analysis of conventional karyotype illustrated the positions of chromosomes centromeres are submedian region(sm)and subterminal region(st).Six cultivars,‘Spring Green',‘Daydream',‘Ile de France',‘Candy Prince',‘White Prince',‘Negrita',were 3A type,three cultivars,‘Flaming Flag',‘Rio Carnival',‘Red Impression',were 3B,one cultivar,‘Queen of Orange',were 4A.3.FISH showed that 5S rDNA loci were located on every chromosomes and most were near the centromere;45S rDNA loci were all located at the end of the long arm of the chromosome and the their signals were much less than 5S rDNA is less.Horever,triploid Tulipa cultivars ‘Negrita' has no rDNA locus in second chromosome.It has little difference in the quantity of 45 S rDNA locus between diploid and triploid.Illustrate the quantity of 45 S rDNA in every genome become less among with the increasing ploidy levels.This phenomenon needs to be further studied.4.The pollen germination rate of Tulipa cultivars are as follows: for diploid cultivars,they ranged from 21.78 percent to 49.51 percent,while that of triploid is close to 0.These results illustrated the diploid cultivars are from intraspecific or closely related species hybridization.In a word,the present research preliminarily indicated that,most Tulipa cultivars are diploid,they are possibly from the different types of intraspecific or closely related species,while the triploid might be from sexual polyploidization or hybrid of diploid and tetraploid.It would be beneficial to cultivate the new Tulipa cultivars.