Genetic Diversity Of Large-flowered Chrysanthemum

Chrysanthemum×morifolium Ramat.,which belongs to Chrysanthemum and Compositae,is much loved by Chinese people as a traditional flower with a history of more than one thousand and six hundred years..Since the Compositae is the most advanced group in angiosperm,the cultivars of C. morifolium were deemed to be situated on the peak of the evolution owing to long periods of cultivation, natural selection and artificial crossing.As a result of numerous cultivars,abundant morphological variation,powerful suitability,wide distribution and extremely complicated genetic background,the investigation,classification,identification and diversity analysis of the cultivars became to be very difficulty,which restricted the breeding and landscape application furtherly.On the basis of investigation and identification of the cultivars of large-flowered chrysanthemum in Beijing area,the genetic diversity of phenotypic character and genic differences were analyzed under the condition of controlled cultivation,the system of probability grading for quantitative characters was built and some characters with bigger variation width and greatest impact in classification were screened out in order to provide the basis for collection,preservation and reasonably application and reference for classification, identification,protection and breeding of the cultivars.The main results were as follows:1.The investigation of cultivars resource Through the author's survey and record in 6 year,we got 1001 cultivars of large-flowered Chrysanthemum in Beijing.The results of statistic analysis showed: the Flat-petaled Group(42%) and Quilled-petal Group(33%) took the most part of cultivars in the 5 groups,whereas the Anemone-petal group(2%) had even less cultivars.The Globular Types(205), Reflexed Types(97) and Mobile-petaled Types(86) had the most cultivars in 30 flower types,but the Tubular-globular Types and the Whole Anemone Types only had one rare cultivar.The white(226,23%) and the yellow cultivars(213,21%) were the two greatest teams in the 9 groups of flower colors, whereas the red(29),green(29) and orange(15) cultivars were much fewer.The colors distributed in different flower types were unever.Only the Reflexed Types,Mobile-petaled Types,Open bead Types and Tubular-pan Types had all nine colors;all of the other 26 flower types existed deficiency of flower color in various degrees.Additionally,a lot of mistake with homonym and synonym phenomenon still existed in the production..2.The probability grading for quantitative characters 400 large-flowered cultivars were chosed and their eighteen chief quantitative characters were tested and recorded according to the test method of morphological characters in the .The empirical distributions were determined by nonparametric test after the distribution range,mean value and variation coefficients of these characters were calculated and frequency diagrams were drawn.The results indicated that 13 quantitative characters(petiole length, leaf length,inflorescence diameter,peduncle diameter and so on) obeyed to the normal distribution, whereas the other 5 characters(floret width,internodes length,peduncle length,number of ray flowers and number of disc flowers) agreed with skewed distribution,in which the number of disc flowers was the most special character with extreme skewness.The grading criterials of the 13 quantitative characters obeyed to the normal distribution were determined with the method of probability grading, the grading criterials of another 5 characters were calculated on the basis of their actual test values. these criterials were moderately adjusted in less than 1/10 of standard deviation for practical application.3.The distribution of the qualitative characters The performance of the 39 chief qualitative characters were observed and recorded,according to the test method of morphological characters in the .The results of distribution proportion of each character in cultivars group showed that the distribution of 32 characters(number of ray flower rings,floret curliness,shape of leaf base,size of stipule and so on) were very asymmetrical with near or above 70%cultivars concentrated upon one or two performance, however,the distribution of the other 7 characters(floret type,surface color of outer floret,back color of outer floret,color of disc floret,claw in base of sinus between lateral lobes,stem erectness and stem color) in the cultivars group were relatively symmetrical. 4.The stability and variation of the characters The results of every character's variation coefficient indicated that they all had higher diversity,the variation coefficient of floral characters is higher than that of foliar.The characters evolved almost independently according to the R cluster analysis of 22 stable characters.The principal component analysis showed that the number of ray flowers, the floret length,height from point of attachment of involucral bracts to top of flower head,floret type and height should be the most important factors.The second principal component contained the surface and back color of outer floret,which followed by the disk flower part diameter and the length of corolla tube. The fourth principal component included some factors about the stipule.5.Research of ISSR molecular marker The Genetic Diversity of 150 cultivars with typical representation in large-flowered chrysanthemum were investigated using 10 primers with clear bands and steady repetitiveness chosen from 50 ISSR primers.A total number of 229 bands were amplified,of which 150 were polymorphic loci.The main index were:PPB=96.07%,He=0.3485,I=0.5154(at species level).The genetic variation in each floral types were quite high,in which the Flat-petaled group is highest(PPB=95.20%),whereas the Anemone-petal group(PPB=86.90%) and the Spoon-petaled group(PPB=%9.52%) were the lowest.UPGMA cluster analysis which according to genetic similarity among floral types indicated that 5 groups were clustered into two groups,the Anemone-petal group was one group solely;the other four groups grouped together,in which the Flat-petaled group and the Quilled-petal group clustered firstly,followed by the Spoon-petaled group and the Filiform-petal group.The results above showed:(1) The cultivars of large-flowered chrysanthemum are widely distributed in Beijing area with plentiful floral types and floral colors;(2) The cultivars with the rare types and colors are urgent for protection;(3) Most of the quantitative characters obeys to the normal distribution,some important traits agreed with skewed distribution.The probability grading can assist quantitative character in establishing new grading standards;(4) Most of qualitative characters is asymmetrical in cultivars,which might be caused by unbalanced differentiation of characters or linkages coming from emphasis characters selection;(5) The floral characters are relatively stable and have comparably large influence on classification,the characters of stipule also have a certain degree of stability and can act as an reasonable supplement for cultivars classification,but the foliar characters have worse stability and can only be recognized as lower level criterion.(6) The genetic relationship among the Flat-petaled group,the Quilled-petal group and the Spoon-petaled group are closest,which followed by the Filiform-petal group because of long-term selection pressure for the specialization of the petal tip loved by most people.The Anemone-petal group has further genetic relationship with these four groups.(7) ISSR molecular marker detection indicates that the proportion of polymorphic loci of lardge-flowered chrysanthemum is higher,in which the Flat-petaled group has the highest genetic diversity level.