The Studies On Taxonomy Of Subgenus Yulania Based On Morphology,Palynology And SSR Markers

Subgenus Yulania is a branch of Magnolia L.in Magnoliaceae.As one of the traditional flowers in China and also an important source of landscape trees and herbs,Subgenus Yulania,which has a long history of cultivation,it is of great value to researching the phylogenetic evolution of Magnoliaceae.However,interspecific hybridization and overlapping of species in Magnoliaceae may lead to many disputes over the classification of genera.Important germplasm of subgenus Yulania was collected from Beijing,Hangzhou,Guangzhou,Xi'an and other places in China.Phenotypic markers,pollen markers and SSR markers were used to analyze diversity and phylogenetic relationships of 14 subgenus Yulania.DNA fingerprints and comprehensive exploration of the classification of subgenus Yulania grouping problem would provide the basis for solving the magnoliaceous classification system.The main research conclusions are as follows:(1)33 indexes of morphological markers were selected.After R cluster and principal component analysis,the indexes were determined.The number of stamens,the thickness of branches and the leaf shape index were all above 0.731,and the contribution rate of principal components was larger,which was the important index of classification.A dendrogram of genetic relationship of some subgenus Yulania germplasms was constructed by Q cluster.Section Buergeria,sect.Yulania,and sect.Tulipastrum were divided at the genetic distance,which were in accordance with the views of Dandy(1964)and Liu Yuhu(1984),indicating that the selection and determination of the characters were reasonable.(2)The dendrogram of the genetic relationship of the subgenus Yulania was constructed.When the genetic distance at 6.13,the classification grouping result consistent with the result by phenotypic markers.The evolution sequence of the germplasm of the subgenus Magnolia was obtained by pollen surface decoration:Magnolia denudata,Magnolia praecocissima,Magnolia×soulangeana,and Magnolia denudata 'Fei huang' were relatively primitive,and Magnolia biondii,Magnolia sprengeri and Magnolia liliflora were relatively evolved,and the degree of evolution of Magnolia amoena,Magnolia wufengensis and Magnolia cylindrica is higher.(3)18 pairs of polymorphic primers were screened out for genetic diversity and phylogenetic relationships among 14 subgenus Yulania,4 subgenus Magnolia and 5 Michelia.STR detection showed that 23 materials could be well amplified.A total of 251 alleles were obtained from 18 pairs of primers,with a polymorphic ratio of 100%.The content of PIC varied from 0.7508 to 0.9482,with an average of 0.8794.The Nei's gene diversity index is 0.4998,the smallest is 0.0430,and the Shannon information index is 0.1057?0.6929 and the average value is 0.2135.There was a certain genetic difference in the tested materials,and had high genetic diversity level.(4)Using the polymorphism information content of 18 pairs of primers and the index of Shannon,23 fingerprints of the subgenus Yulania and its related species were constructed,which can distinguish 23 materials and discriminant ploidy information,and enrich the fingerprint database of the subgenus Yulania.According to the fingerprint,the Michelia and subgenus Magnolia are diploid species,and the boundary is clear.(5)The clustering results of SSR markers showed that the distinct groups were in Michelia,subgenus Magnolia and subgenus Yulania.Each group had a common point of higher morphological similarity,similar flowering time and ploidy.The subgenus Yulania is closely related to Michelia and is far from the subgenus Magnolia,but the boundary is obvious.It is not recommended to combine Michelia and subgenus Yulania.The relationship of Magnolia amoena and Magnolia cylindrica is close.So do Magnolia liliflora and sect.Buergeria.Magnolia acuminata 'Yellow Bird' from America is far away from all kinds of Magnolia in China.(6)Based on the comparative analysis of morphology,palynology and SSR markers,subgenus Yulania can be roughly divided into 4 subgroups.On the basis of the section Buergeria,sect.Yulania and sect.Tulipastrum,it is suggested to increase the sect.Soulangeana and Magnolia wufengensis was classified as subgenus Yulania.It is not recommended that combine the sect.liliflora and sect.Buergeria.