Research On The Influence Of Electroplating Process On Studies On Population Genetics And Domestication Of Panicum Miliaceum

Broomcorn millet(Panicum miliaceum L.),one of the earliest domesticated cereals in the world,is widely cultivated in Eurasia,North America,and Australia.Weed broomcorn millet(Panicum miliaceumsubsp.ruderale),the associated weed of broomcorn millet,is also widely distributed in various cultivated areas of broomcorn millet.The studies on itswild ancestors,domestication area(s)in China,and spread routes have been the focuses of research onthe origin of broomcorn millet.Based on the chloroplast DNA(cpDNA)non-coding sequence,this study analyzed the genetic diversity of boormcorn millet and the phylogenetic relationships in Panicum and discussed the relationship between broomcorn millet and its weed form.Besides,the population genetics of weed and cultivated broomcorn millet were compared based on simple sequence repeat SSR(SSR)markers,and the genetic relationship between them was revealed.Meanwhile,the domestication area(s)and the spread routes of cultivated broomcorn millet were further explored.The main results of this study are as follows:1.Study on genetic diversity and domestication of broomcorn millet based on cpDNA sequenceAnalysis of intraspecific genetic diversity among 6 broomcorn millet accessions was conducted using 8 cpDNA noncoding sequences and the phylogenetic relationship in Panicum was explored using one of those regions,trnH-psbA.The results show thatthe cpDNA noncoding sequences are relatively conserved in broomcorn millet,while polymorphisms in those regions are foundin Panicum.The results of this study show that Panicum milliaceum clustered together with their possible ancestors,Panicum capillare,but relatively distant from another possible ancestor,Panicum repens in the tree of Panicum.2.Study on population genetics and domestication of broomcorn millet based on SSR markersPopulation geneticsanalys is of weed and cultivated broomcorn millet distributed in various regions were carried outusing 200 accessions based on 23 SSR markers.The results show that:(1)The genetic diversity of the weed broomcorn millet populations was generally higher than that of cultivated broomcorn populations,while did not differ significantly the genetic diversity of Chinese and foreign cultivated broomcorn millet.(2)The genetic variation resided within population,rather than among populations,between Chinese and foreign cultivated broomcorn millet,or between weed and cultivated broomcorn millet.Frequent genetic flow was found among populations.(3)Structure analysis results show that: Forthe cultivated broomcorn millet,the southern part of Eurasia is dominated by the red gene pool,while the red and green gene pools account for a certain percentage in the northern part of Eurasia.However,the samples of blue gene pool arevery rare which is only found in Poland,Central Europe.Forthe weed broomcorn millet,the red gene pool is mainly distributed in the Loess Plateau,the green gene pool is found onlyin Northeast China,and the blue gene pool is widely distributed as the main typeof the weed broomcorn millet.(4)Principal component analysis(PCA)based on the gene poolsdivided by Structure indicated that the red,green,and blue gene pools were well separated,and some weed and cultivated accessions belonging to the same gene pool from the same region showed very close genetic distance.(5)Cluster analysis of different gene pool groups in differentareas showed that the red,green,and blue gene pool groups were clustered into three branches separately.On both red and green gene pool branches,the weed and cultivated groupsfrom the same and adjacent areas were found clustered together,and the Chinese and foreign cultivated groups separated from each other.(6)The results of bottleneck analysis show that recent bottleneck effect has not been found in weed,Chinese cultivated,and foreign cultivated broomcorn millet.In summary,we concluded that:(1)The cpDNA noncoding sequences have limitations in the studies of the population genetics,the domestication and the spreadof cultivated broomcorn millet,but it is more suitable for the studies of the origin of this cereal and the relationships between the cereal andtheir wild relatives.The possible ancestor of broomcorn millet,Panicum capillare,probablyhas maternal kinship with it;while the other probable ancestor,Panicum repens,may be far from it in maternal kinship.(2)Weed broomcorn millet may be the direct wild ancestor of cultivated broomcorn millet.(3)There may be at least two independent domestication areas in China for the cultivated broomcorn millet.The red gene pool of broomcorn millet was domesticated in the Loess Plateau,and the green gene pool of broomcorn millet was domesticated in the Northeast China.(4)After being domesticated in the Loess Plateau of China,the red gene pool was spread westward to Xinjiang,Central Asia,West Asia,and reached Central Europe eventually,The green gene pool began in Northeastern China,and spread to Eastern Europe via Mongolia,Russia and Ukraine.Those two westward routes of broomcorn milletcoincide exactly with the prehistoric Oasis Silk Road and the Grassland Silk Road respectively.In this study,several issues such as the wild ancestor,the domestication areas,and the spread routes of broomcorn millet were deeply explored.Significant genetic information,clues,and stagedresults were obtained.These results will provide important evidence for the researches on the population genetics,the domestication,and the germplasm conservation of this cereal.