Genetic Diversity Of Medicago L. Germplasm Resources In Xinjiang

Genetic variations are greatly accumulated when Medicago L.make adjustment to the changeable geographic environment and ecologic conditions.Desirable traits such as good resistance to drought,cold and barren make them important genetic resources for alfalfa breeding and quality improvement.In this study,genetic diversity of 36 wild populations are collected from Xinjiang area to be ananlysed at morphological,cytological and SSR molecular levels.Main results as follows:?Nineteen morphological traits analyzed show significant variance among the populations studied and pods dehiscent showed significant variances with the coefficients of variation to be 48.79 percent,no significant variance occur in the node number.Results of principal component analysis revealed that several traits,such as stem length,lateral root number,dehiscent,stem color,one thousand seeds' weight and seed number for each pod were the main factors for morphological diversity.Based on the morphological data,36 accessions were clustered into seven groups.The results of clustering showed some rules in the geographical distribution.The three species(subspecies)can not be distinguished clearly by these morphological traits.Because the number of seeds are too less to proceed the next chromosomal and SSR molecular marker analysis,6 accessions have to drop out.?Thirty populations are divided into two ploidy levels,and the basic number of chromosome was x=8.Three populations of M.falcata show 2n=16 and the others show 2n=32.Populations belonging to both M.sativa and M.varia show 2n=32,and there are no aneuploidy exists.Three chromosomes types(m,sm,and st)are included among thirty populations,with two pairs of st chromosomes are observed in M.sativa and M.varia,respectively.B-chromosomes existed in the MZS-H population,and their number vary from 3~4 in a single cell.According to the standard of symmetry for chromosomes,thirty populations were divided into four types(1A,2A,1B and 2B).The degree of karyotype evolution is M.falcata >M.sativa>M.varia.?In this study,10 SSR markers for 30 wild Medicago populations showed a relatively high level of genetic diversity(PIC=0.725).Genetic differentiation among populations of M.falcata and M.varia was higher.AMOVA analysis of molecular variance indicated that the genetic variation mainly existed within populations.Four clusters were detected from UPGMA clusters,and the three populations of M.varia tend to be grouped together with populations of M.falcata.As the similar results of morphological cluster,populations collected from similar region grouped together.