The Genetic Structure And Relation Among Maize Populations Based On SSR

In china,the narrow genetic base is one of the major limitative factors for the germplasm development in maize breeding.Germplasm enhancement, improvement and innovation is the only way to solve this problem.To study the genetic structure and diversity of different populations,even and genetic relation between populations is significantly for the improvement,innovation and rational utilization of germplasm.In our study,we used two maize populations Golden Queen and Yu Syn5 as basic materials,established a logical analytic method of SSR through compare the different DNA sampling and estimating method of SSR which used in the research of genetic diversity and genetic distance.At the same time,we analysed the genetic structure of two populations.Then,we researched the genetic diversity and genetic relation of 12 improved populations,which represented main heterosis groups of maize germplasm and different sources,and compartmentalized different heterosis populations by the clustering analysis.We also studied genetic variation characters of different generations of Golden Queen using the Golden Queen population which improved by recurrent selection for material.The main results as follows:1.In present study,the genetic diversity between two populations were compared and analyzed by 50 pairs of SSR primers,and using 60 individuals DNA samples of Golden Queen and YuSyn5 maize populations with 6 treatments(the individual DNA samples,the mixed DNA samples with 5 individuals,10 individuals,15 individuals, 20 individuals,and 30 individuals,respectively).The results indicate that the frequencies of alleles which detected by using the individual DNA samples was very low,and detected that allele number decreased gradually and the frequency of missing alleles increased along with the increaseing of mixed individuals in the treatment.The mixed DNA samples with 10 individuals is the best sampling strategy in the 6 ways of individual DNA sampling.2.The results of the genetic distance between two populations calculated by three models suggested that the genetic distances GD,GD_(J)and GD_(N)showed a gradually increasing trend along with the increasing of the mixed individual number,but the increasing extent of GD_(J)and_(N)was wider.There was an obvious deviation between GD_(J),GD_(N)from mixed samples and the GD from 60 individual DNA samples based on allele frequency.We based on the results and the comparison of the genetic distances based on different calculation methods.When the genetic diversity and polymorphism in maize populations are studied by SSR,the Nei's genetic distance GD_(N)and Jaccord's genetic distance GD_(J)are calculated according to 0,1 data,(GD_(N)+GD_(J))/2 will be calculated close to the genetic distance by allele frequency of individuals.3.The comparation of polymorphic loci,mean heterozygosity,genetic distances, and the category and frequence of genotype of the two populations by SSR molecular marker,showed that the two populations had abundant genetic diversity,and the YuSyn5' was more abundant.4.202 alleles of 12 populations were detected by using 56 pairs of SSR primers.2 to9 alleles were detected per locus and the mean value is 3.61.The results indicated that the genetic variation of 12 populations is abundant.The number of alleles over the 12 populations ranged from 112 to 143,and from 2 to 2.25 per locus.The variation of Huangjin populations was the most abundant,and Liaolu Syn was the least.Basing on the genetic distance,we clustered the 12 populations into 6 heterosis populations:Golden Queen,Reid,Tangsipingtou,Lvdahonggu,Tuxpeno tropic and subtropic germplasm.The first category is Siyi population,137 population,Goden Queen and Huangjin population.The second is YuSyn5.The third is Zsyn5.The fourth is LiaoluZyn.The fifth is Pob21.The sixth is Pob501,Pob26 Huangmo49 and ZiT36.The result of compartmentalizing is as the same of the fact.5.Basd on the allelic strap and allelic combined strap of 16 pairs of SSR primers, 12 populations were completely identified from each other.We could use one maker to differentiate Golden Queen,Pob21,Siyi population,Zsyn5,YuSyn5,137population, Liaolvzong from each other,use two makers to differentiate Huangjin population and Huangmo49,and use three makers to differentiate ZiT36.6.56 pairs of selected primers,we detected 135 allelic loci in 5 generations of golden queen of recurrent selection improvement population.The mean number of allelic loci was 2.41.Different recurrent improvement populations had definite diversity.The results suggested that improved population still had abundant genetic diversity,which could support the further improving and breeding of maize.