Studies On Genetic Relationships Of Taraxacum Kok-saghyz With 10 Congeneric Species

Plants of Taraxacum F.H.Wigg.are important plant resources with ornamental medicinal edible and industrial valus.They are mainly distributed in the central region of the Northern Hemisphere temperate and subtropical,and distributes around China except the Southeast and Southern provinces.Xinjiang is one of the most important distribution areas about Taraxacum in China.Taraxacum kok-saghyz is also named the Russian dandelion,and is a natural rubber plant T.kok-saghyz is compositae perennial plant and native to Kazakhstan and Xinjiang.Because the high content??20%?of natural rubber,and the excellent rubber quality,it is viewed as the best natural rubber plant resource besides Hevea brasiliensis,which has high economic value.The evolution of Taraxacum complex floristic geography special,plant ploidy breeding methods lead to complex,this genus is also more complex,multiple species often mixed in the same area,interspecific hybridization phenomenon,the genus showed abundant genetic diversity,classification problems brought difficult to identify T.kok-saghyz germplasm resources.In order to fully understand the plant resources of Taraxacum species in Xinjiang,the variation pattern of characters,variation and interspecific relationships were studied on T.kok-saghyz and its 10 relative species in Xinjiang,their morphological traits,pollen morphology and seed coat micromorphology were observed.The results would offered bases for the cultivation of high rubber content T.kok-saghyz cultivars and establishment of the core collection,and also provide the basis for genetic study,domestication and cultivation.The main results are as follows:?1?Variance analysis,factor analysis and cluster analysis were carried out on the phenotypic characters of Taraxacum kok-saghyz Rodin and its 10 Congeneric species,according to the research results of 59 characters:Taraxacum plant phenotypic diversity,the coefficient of variation was between7.5⁶7.44%,the average genetic diversity index was 1.136,the number of morphological traits diversity index is higher than the quality traits.A total of 7 principal components were extracted by factor analysis of59 characters,with a cumulative contribution rate of 84.767%.Factor analysis showed that the floral morphological characters variation was a major factor contributing to the phenotypic differentiation of Taraxacum.Phenotypic clustering results show that 13 collections were divided into 4 groups at a genetic distance 7.5,and the species collected from the same region tended to be clustered into the same groups,indicating close relationship,while the 3 collections of Taraxacum kok-saghyz Rodin were clustered into 2different groups showing distant relationships.?2?Studies on pollen micromorphology of Taraxacum,Taraxacum plant pollen exists in the form of single-grained,the hexagon in polar view and circular equatorial plane.Pollen nearly spherical or nearly flat spherical,polar axis size between 16.18³7.53?m,equatorial axis size between 16.88⁴1.4?m.P/E did not change significantly,of which P/E is the largest Mosowan populations of Taraxacum kok-saghyz is 0.96,P/E is the smallest Taraxacum erythrospermum is 0.85.The germination holes are hollow,with 3germination holes,and the holes are nearly flat,round or nearly round;There were no significant differences in the size of germination pores among different Taraxacum species.Among them,the pollen germination of Zhaosu Taraxacum kok-saghyz was the smallest.For the spiny exine sculpture,not a broad ridge,spinulate raised ridge density is different,the largest Taraxacum monochlamydeum(0.44±0.18?m^-2),the smallest for the Zhaosu Taraxacum kok-saghyz(0.18±0.03?m^-2).Based on the morphological characteristics of pollen,there are significant differences among species of Taraxacum.It has taxonomic significance and can be divided into 3 groups of 11 test materials.?3?The morphological observation of the testa of Taraxacum plants showed that the achenes were mostly cylindrical or inverted cone,achene grows in 2.47³.23 mm,wide between 0.56⁰.83 mm,among them,achene is the largest Taraxacum officinale?3.23×0.83 mm?,and other dandelion things are different significantly.Achenes are mostly light brown,followed by dark brown and reddish brown.The upper small fruit body evenly,and white spots small protrusions,smooth or lower spinulate,different between small size and density are different;cone suddenly collapsed or shrunk gradually,the surface with a small,cone length and achene length ratio?cone length/achene length without cone length?is a fixed value.The morphological characters of the testa of Taraxacum are stable.The species can be divided into 4 groups based on the micro morphological characteristics of achene and seed coat.The 13 species can be divided into two groups.