Chromosome Karyotype Studies on Different Populations of Xanthopappus sub-acaulis(Asteraceae),an Endemic Species from the Qinghai-Xizang Plateau
In order to investigate the evolutionary trends and phylogenetic relationships among six different natu-ral populations of Xanthopappus subacaulis,we analyzed karyotype characteristics by chromosome conventional slicing technology.The result showed that:(1)The chromosome ploidy of 6 X.subacaulis natural populations was diploid,with the basic number of chromosomes being nine and no extra chromosomes.(2)The centro-meric type was consistently identified as the centromeric subtype(m)and the karyotype formula was 2n=2X=18=18m for all X.subacaulis populations.With the exception of P002 and P004,lack of the short(S)type,the remaining four populations included long(L),medium-long(M1),medium-short(M2),and short(S)chro-mosome types.(3)Among 6 populations of X.subacaulis,all of the karyotype type was 1A,the average arm ratio ranged from 1.13 to 1.39,the length ratio was between 1.61 and 1.78,and the nuclear asymmetry coeffi-cient followed by 54.76% to 55.69% .In these populations,P004 exhibited the largest average arm ratio and nuclear asymmetry coefficient,suggesting that it should have the higher evolutionary position.(4)When the genetic distance was 4,P001 and P002 clustered into a single branch.Similarly,when the genetic distance was 1,P003 and P004,as well as P006 and PH52,formed into two branches,respectively.Within same branch,each population had the closer relationships.This study firstly discussed the chromosomal karyotype characteristics,as well as the evolutionary trends and phylogenetic relationships among 6 populations of X.subacaulis,which provides cytological data for the study of karyotypes and systematic evolution of Xanthopappus and even the Asteraceae family,also serves as basic data for sequencing and assembling the genome of X.subacaulis and dis-covering the key metabolic pathway genes involved in flavonoid synthesis.
万方数据
维普
