Investigation On Ploidy Levels Of Tulip Cultivars And Analysis Of Their Interspeceies Crosses

The genus Tulipa of the Liliaceae family is the most important bulbous ornamental flowers, which is one of the most famous cut flowers in the world.Tulipa cultivars are mostly diploid, few are polyploid.But polyploid cultivars have higher ornamental value and strong resistance to disease and viruses.Therefore,the most important work of tulip breeding is to cultivate polyploid varieties. Currently more than10,000kinds of tulips cultivars have been hybridized, which provide a rich breeding material for tulipa crossing.In our experiments, the ploidy, pollen germination, pollen morphology and stomata of15tulip cultivars were measured, on which10tulip cultivars were detected by fluorescence in situ hybridization. This experiment also analysed the hybridization of ’2x×2x/4x’ and ’3x×2x/4x’.The results were summarized as follows:1.Among the15tulip cultivars which are imported from the Netherlands,six of them (’Dow Jones’、’Cheers’、’Leen var der Mark’、’Merry Christmas’’Negrita’、’Unknown’) are diploid(2n=2x=24),eight of them (’Apeldoorn’’Barcelona’、’Red Impression’、’World’s Favourite’、’Lefeber’s Memory’’Kingsblood’、’World Fire’、’Oxford’) are triploid(2n=3x=36),one of them (4Red Power’) are tetraploid(2n=4x=48).2.The pollen morphology of15tulip cultivars can be divided into two categories: one is normal stainable elliptical pollen,the other is abnormal unstainable wrinkled pollen. For pollen morphology, tetraploid’Red Power can reach70.3%,which is much higher than others; the normal rate of pollen morphology of diploid varieties ranges from31.4%to68.7%; the normal rate of pollen morphology triploid varieties ranges from2%to37.3%.3.The pollen germination experiments showed that tetraploid’Red Power’has40.1%pollen germination rate, which is higher than diploid and triploid cultivars.The rate of pollen germination of six diploid ranges from17.3%to27.2%, The rate of pollen germination of eight triploid is less than2%. By comparison we can find that pollen morphology rate is significantly higher than normal pollen germination rate, which is mainly due to the pollen morphology indicates that the potential pollen germination, and pollen germination indicates that the actual germination capacity of pollen. 4. All tulip cultivars have stomata in upper and lower epidermis, the upper epidermis stomata are mostly spherical, the lower stomata epidermis are mostly oval. Among them, the density of upper and lower epidermis stomata of Unknown’、’Barcelona’、’World’s Favourite’ is similar。The upper epidermis stomatal density of ’Cheers’、’Leen var der Mark’、’Merry Christmas’、’Apeldoorn’、’Red Impression’、’Lefeber’s Memory’、’Kingsblood’is less than the lower epidermis stomatal density.The upper epidermis stomatal density of ’Negrita’、’World’s Fire’、’Oxford’is greater than the lower epidermis stomatal density. Different ploidy tulip varieties vary widely between stomatal density, diploid, the maximum number of upper and lower epidermis stomatal times back triploid, tetraploid at least.5.45SrDNA was mapped on the chromosome of10tulip cultivars using fluorescence in situ hybridization (FISH). The results showed that,45SrDNA sites are all located in the long arm of chromosome ends and only one45SrDNA sites are located on each chromosome, different varieties of45SrDNA number of sites and locations are also different.6. The fruits of both2x×2x and2x×4x crosses develop well.By embryo rescue,1722hybrid seedlings were obtained from19fruits of2x×2x;455hybrid seedlings were obtained from18fruits of2x×4x. Relatively silent, the2x×2x times of less than2x×4x hybridization barriers between ploidy hybridization barriers.2x×2x and2x×4x the reciprocal cross experiments also demonstrated significant or not parental genotypes of hybrid success.7. The hybridization success rate of3x×2x/4x is low, which means crossing barrier of3x×2x/4x is relatively large. By embryo rescue,335hybrid seedlings were obtained from24fruits of3x×2x;35hybrid seedlings were obtained from14fruits of2x×4x. The success of3x×2x/4x shows that tulip cultivars have tetrasporic Fritillaria-type embryo sac. So male-sterile tulip cultivars could be used as seed parents to cross with appropriate males.