Analysis of genetic diversity and population structure in sweetpotato using SSR markers

Sweetpotato, Ipomoea batatas(L.) Lam., is an important food crop worldwide. Large scale evaluation of sweetpotato germplasm for genetic diversity is necessary to determine the genetic relationships between them and effectively use them in the genetic improvement. In this study, the genetic diversity of 617 sweetpotato accessions, including 376landraces and 162 bred varieties from China and 79 introduced varieties from 11 other countries, was assessed using 30 simple sequence repeat(SSR) primer pairs with high polymorphism. Based on the population structure analysis,these sweetpotato accessions were divided into three groups, Group 1, Group 2 and Group 3, which included 228, 136and 253 accessions, respectively. Consistent results were obtained by phylogenic analysis and principal coordinate analysis(PCoA). Of the three groups, Group 2 showed the highest level of genetic diversity and its accessions were mainly distributed in low-latitude regions. The accessions from South China exhibited the highest level of genetic diversity, which supports the hypothesis that Fujian and Guangdong were the first regions where sweetpotato was introduced to China. Analysis of molecular variance(AMOVA) indicated significant genetic differentiations between the different groups, but low levels of genetic differentiation existed between the different origins and accession types.These results provide valuable information for the better utilization of these accessions in sweetpotato breeding.

Genotypic Diversity Affects Age Structure of Tiller and Rhizome of Leymus chinensis Population,But Not Age Structure of Bud

The effect of genotypic diversity on the age structure and bud bank of the Leymus chinensis population has not yet been demonstrated.This experiment was designed to study the age structure of the tiller,rhizome,and bud of L.chinensis at genotypic diversity levels of 1,2,4,8,and 12.A total of 64 communities were established in this experiment,following the principle of randomized block experimental design.The results indicated that genotypic diversity had a significant or obviously significant effect on the cumulative length of rhizomes of 2a and 4a,dry matter accumulation of rhizomes of 1a and 2a,tiller number of 1a,tiller productivity of 3a,but had no significant effect age structure of buds.As the levels of genotypic diversity increased,the proportion of the cumulative length of rhizomes with 4a decreased and then increased,and dry matter accumulation of rhizomes with 1a and 2a gradually increased while the number of tillers with 1a gradually decreased,when the gradient of genotypic diversity increased.At the 1,2,4,8,and 12 genotype diversity levels,the number of tillers,the cumulative length of rhizomes,and dry matter accumulation in rhizomes and buds were all age structures of expanding type.However,tiller productivity was an expanding or stable age structure at levels of 1,2,4,8 genotypic diversity,while it was a declining age structure at the 12 genotype diversity gradient.An appropriate genotypic diversity is conducive to maintaining the growth and stability of the age structure of L.chinensis population,but too high a gradient of genotypic diversity can have a negative impact on the population age structure.This study provided that an appropriate number of genotypic diversity contributes to the stability of the population.

Genetic Diversity,Population Structure,and Genome-Wide Association Study of Seven Agronomic Traits in 273 Diverse Upload Cotton Accessions

Upland cotton(Gossypium hirsutum)is the most important plant producing natural fibers for the textile industry.In this study,we first investigated the phenotypic variation of seven agronomic traits of 273 diverse cotton accessions in the years 2017 and 2018,which were from 18 geographical regions.We found large variations among the traits in different geographical regions and only half of the traits in either years 2017 or 2018 followed a normal distribution.We then genotyped the collection with 81,612 high quality SNPs.Phylogenetic tree and population structure revealed a diverse genetic structure of the core collection,and geographical diversification was an important factor,but account for part of the variances of genetic diversification.We then performed genome-wide association study for the seven traits in the years 2017 and 2018,and the average values of each trait in the two years,respectively.We identified a total of 19 significant marker-trait associations and found that Pollen Ole e 1 allergen/extension could be the candidate gene associated with the fall-off cotton bolls from the last three branches.In addition,large variations were observed for the heritability of traits in the years 2017 and 2018.These results provide new potential candidate genes for further functional validation,which could be useful for genetic improvement and breeding of new cotton cultivars with better agronomic performances.

Genetic Diversity in Wild Populations of Poacynum hendersonii from Inland Arid Regions of Northwest China

[Objective] Study on the genetic diversity in wild populations of Poacynum hendersonii.[Method] Random amplified polymorphic DNA(RAPD)technique was employed to analyze the genetic diversity in five wild populations of P.hendersonii sampled from Xinjiang,Gansu and Qinghai provinces.[Result] Totally 165 clear and repeatable bands were generated in RAPD reaction by using 20 primers screened from 80 primers,of which 110 were polymorphic,accounting for 66.67%.At species level,Nei's gene diversity index(H),Shannon's information index(I)and genetic differentiation coefficient(Gst)were 0.220 5,0.304 7 and 0.908 2,respectively.P.hendersonii germplasm resources share a high level of genetic diversity,and genetic differentiation mainly exists among the populations.Results from genetic distances and cluster analysis showed that relationships among P.hendersonii populations were to some extent related with their geographical and climatic characters.[Conclusion] This study suggests that the conservation of P.hendersonii should focus on the protection of many populations,particularly the Qinghai population.

Population Genetic Diversity in Chinese Pomegranate (Punica granatum L.) Cultivars Revealed by Fluorescent-AFLP Markers

Eighty-five pomegranate （Punica granatum L.） cultivars from six geographical populations located at Shandong, Anhui, Shaanxi, Henan, Yunnan, and Xinjiang Provinces were studied for its population genetic diversity by means of fluorescent-AFLP markers. The results indicated that 135-185 polymorphic loci were amplified by eight pairs of primers at species level. An average of 158.25 polymorphic loci was amplified for each primer combination. The polymorphism percentage ranged from 62.5% to 86.11%, and the average polymorphism percentage was 73.26%. This indicated that there was plentiful genetic diversity in pomegranate cultivars. The genetic diversity at the species level was higher than that at the population level. The order of the genetic diversity was Henan population 〉 Xinjiang population 〉 Shaanxi population 〉 Anhui population 〉 Shandong population 〉 Yunnan population. Variance analysis showed that there was significant difference between populations in genetic diversity. The genetic differentiation coefficient between populations （Gsr） was 0.2018, which indicated that gene differentiation was mainly within the population, and between populations, it accounted for 20.18% of the total variation. Gene flow （Nm） between the populations measured was 1.9027 based on the genetic differentiation coefficient between populations, indicating that there was mild gene flow between populations. The UPGMA cluster analysis showed that most accessions from the same population were clustered together, but there was partly gene exchange. All genetic parameters indicated that there was plentiful genetic diversity in pomegranate cultivars in China, of which Henan population was significantly higher than the other populations, and it had wide application foreground in pomegranate breeding in China.

Population genetic structure and diversity of high value vulnerable medicinal plant Acorus calamus in India using RAPD and chloroplast microsatellite markers

Acorus calamus is a highly valued medicinal plant with global distribution used in several drugs of health care systems. We evaluated the genetic diversity and population structure of 50 populations of A. calamus from different geographical regions in India through RAPD and chloroplast microsatellite markers. From the total screened 82 RAPD primers and 18 cpSSR primers, 10 RAPD and nine cpSSRs were found polymorphic. The selected 10 RAPD primers produced a total of 96 reproducible bands, out of which 65 were polymorphic （67.70%）. Whereas, the selected nine cpSSR markers produced 26 alleles and all of them were polymorphic. The mean genetic diversity （H T ） among populations using RAPD （H T = 0.263） and cpSSR （H T = 0.530） markers was higher in comparison to the mean genetic diversity within populations. Mean coefficient of gene differentiation （G ST ） between the populations was also high for both RAPD （G ST = 0.830） and cpSSR markers （G ST = 0.735）, whereas the estimated gene flow was very low for RAPD （Nm = 0.102） and for cpSSR （Nm = 0.179）. AMOVA analysis revealed that more genetic variation resided among the populations than within populations. Significant differences （p 0.001） were observed between the populations and individuals within the populations. Cluster analysis of RAPD and cpSSR data using UPGMA algorithm based on Nei’s genetic similarity matrix placed the 50 populations into two main clusters. The implication of the results of this study in devising strategy for conservation of A. calamus is discussed.

Genetic diversity and genetic differentiation of natural populations of Pinus kesiya var. langbinanensis

Genetic diversity and genetic differentiation of natural populations of Pinus kesiya var. langbinanensis were examined by means of electrophoresis technique. Analysis of 9 enzyme systems including 16 loci showed that all the three natural popu-lations of the pine were high in genetic diversity but low in inter-population genetic differentiation. The proportion of polymorphic loci is 0.667, with each locus holding 2.13 alleles, averagely. The average expected and observed heterozygosity was 0.288 and 0.197, respectively. The gene differentiation among populations was 0.052, but the mean genetic distance was only 0.015.

Allozyme Diversity and Population Genetic Structure of Three Medicinal Epimedium Species from Hubei

Three Epimedium species, E. pubescens Maxim., E. sagittatum （Sieb. ＆ Zucc.） Maxim., and E. wushanense T. S. Ying, which are sympatrically distributed in the western Hubei Province, have been used in traditional Chinese medicine （TCM） for about 2,000 years. Genetic variability and population genetic structure of 11 natural populations of these Epimedium species were investigated using isoelectric focusing in thin-layer polyacrylamide slab gels. Of the 22 enzyme systems prescreened, six coding for 13 loci and 45 alleles were resolved, which were used for analyzing genetic diversity and population structure at both intraspecific and interspecific levels. The results showed that： l） high levels of genetic diversity were observed in all three species （A = 2.6-3.2, P = 69.2%-84.6%, Ho= 0.274-0.377, HE= 0.282-0.369）, which were higher than that of other herbaceous and aulmal-pollinated species with similar life-history characteristics; 2） there was significant deviation from Hardy-Weinberg Equilibrium, with one half of the loci showing heterozygote excess and the other homozygote excess, in all populations, suggesting the complicated breeding system of Epimedium species; 3） the low level of intraspecific and interspecific genetic differentiation （GST= 0.0246-0.0409 and 0.0495-0.1213, respectively） indicated a high level of gene flow among populations and close genetic relationship among the three species; and 4） UPGMA cluster analysis further showed that E. pubescens was more closely related to E. sagittatum than to E. wushanense, which was in good agreement with the morphological characters and the recent phylogenetic analysis of these species. On the basis of these results, it was concluded that the mixed breeding system, long-lived perennial life form, ancient evolutionary history, and seed dispersal by ants in Epimedium are responsible for the genetic variation and population structure of these species.

Balancing selection shapes population differentiation of major histocompatibility complex genes in wild golden snub-nosed monkeys

Small and isolated populations face several intrinsic risks,such as genetic drift,inbreeding depression,and reduced gene fow.Thus,patterns of genetic diversity and differentiation have become an important focus of conservation genetics research.The golden snub-nosed monkey Rhinopithecus roxellana,an endangered species endemic to China,has experienced rapid reduction in population size and severe population fragmentation over the past few decades.We measured the patterns of genetic diversity and population differentiation using both neutral microsatellites and adaptive major histocompatibility complex(MHC)genes in 2 R.roxellana populations(DPY and GNG)distributed on the northern and southern slopes of the Qinling Mountains,respectively.Eight MHC-linked haplotypes formed by 5 DQA1 alleles,5 DQB1 alleles,5 DRB1 alleles,and 4 DRB2 alleles were detected in the 2 populations.The larger GNG population showed higher genetic variation for both MHC and microsatellites than the smaller DPY population,suggesting an effect of genetic drift on genetic variation.Genetic differentiation index(FST)outlier analyses,principal coordinate analysis(PCoA),and inferred population genetic structure showed lower genetic differentiation in the MHC variations than microsatellites,suggesting that pathogen-mediated balancing selection,rather than local adaptation,homogenized the MHC genes of both populations.This study indicates that both balancing selection and genetic drift may shape genetic variation and differentiation in small and fragmented populations.

Microsatellite analysis of genetic diversity and population structure of Chinese mitten crab (Eriocheir sinensis)

Chinese mitten crab （Eriocheir sinensis） has higher commercial value as food source than any other species of Eriocheir in China. To evaluate the germplasm resources and characterize the genetic diversity and population structure of the crabs in different water systems, two stocks and two farming populations were assessed with 25 polymorphic microsallite loci available in public GenBank. Basic statistics showed that the average observed heterozygosity （Ho） amongst populations ranged from 0.5789 to 0.6824. However, a remarkable presence of inbreeding and heterozygote deficiencies were observed. To analyze population structure, pairwise FST coefficients explained only -10.3% variability from the subdivision of mitten crab populations, the remaining variability stems from the subdivision within subpopulations. Although the four populations had slight differentiation, different allelic frequencies resulted in distinct population structures. Two stocks and one farming population were clustered together to the phylogenetic branch of Yangtze crab, with an approximate membership of 95%. Whereas, another farming population was clustered singly to the phylogenetic branch of the Liaohe crab, with a membership of 97.1%. The tests for individual admixture showed that Yangtze crab had probably been contaminated with individuals from other water systems. Genetic relationships between populations also supported the conclusion that Yangtze crab and Liaohe crab had different gene pools in spite of the origins of the same species.

AFLP analysis revealed differences in genetic diversity of four natural populations of Manila clam (Ruditapes philippinarum) in China

The amplified fragment length polymorphism （AFLP） technology was used to analyze the genetic diversities in four natural populations of Manila clam （ Ruditapes philippinarum）, distributed in four sea areas of China, i.e. , the Bohai Sea, the Huanghai Sea, the East China Sea and the South China Sea. Two hundred and sixty-four AFLP loci were analysed in 195 individuals and revealed high levels of genetic diversity. The percentage of polymorphic loci ranged from 92.13% to 96.06% and the Shannon＇ s information index was from 0.256 8 to 0. 275 6. By analyzing molecular variance （ AMOVA）, it was found that there were high levels of genetic differentiation between populations of Qingdao and the other three sea areas. Cluster analysis by Nei＇ s pairwise distances grouped specimens by geographical origin, except the population of Qingdao. A conclusion can be drawn that there are high genetic diversities in the four natural populations of Manila clam in China and some distinct differences existed among and between the four populations. The results also indicated that human cultivation activities will have great influence on the genetic structure of the population of Qingdao.

Analysis of genetic diversity and population structure of Chinese yak breeds (Bos grunniens) using microsatellite markers

Nine Chinese yak breeds （Maiwa, Tianzhu White, Qinghai Plateau, Sibu, Zhongdian, Pali, Tibetan High Mountain, Jiulong, and Xinjiang） and Gayal were analyzed by means of 16 microsatellite markers to determine the level of genetic variation within populations, genetic relationship between populations, and population structure for each breed. A total of 206 microsatellite alleles were observed. Mean F-statistics （0.056） for 9 yak breeds indicated that 94.4% of the genetic variation was observed within yak breeds and 5.6% of the genetic variation existed amongst breeds. The Neighbor-Joining phylogenetic tree was constructed based on Nei＇s standard genetic distances and two clusters were obtained. The Gayal separated from the yaks far away and formed one cluster and 9 yak breeds were grouped together. The analysis of population structure for 9 yak breeds and the Gayal showed that they resulted in four clusters; one cluster includes yaks from Tibet Autonomous Region and Qinghai Province, one cluster combines Zhongdian, Maiwa, and Tianzhu White, and Jiulong and Xinjiang come into the third cluster. Pali was mainly in the first cluster （90%）, Jiulong was mainly in the second cluster （87.1%）, Zhongdian was primarily in the third cluster （83%）, and the other yak breeds were distributed in two to three clusters. The Gayal was positively left in the fourth cluster （99.3%）.

Assessing genetic diversity of wild populations of Japanese flounderusing AFLP markers

Amplified fragment length polymorphism （AFLP） analysis was used to evaluate the genetic diversity of four wild geographical populations of Japanese flounder （Paralichthys olivaceus）. A total of 775 loci （58.32% of which was polymorphic） in the range between 100 and 1 300 base pairs were detected from 110 individuals using seven primer combinations. The percentage of polymorphic loci detected by single primer combination for each population was calculated, ranging from 19.59% to 53.33%. Genetic similarities within and among the populations were calculated from the binary matrices of presence - absence. Phylogenetic tree of four populations was constructed by using the UPGMA method using PHYLIP Version 3.5. According to intrapopulation genetic similarities, CW population displayed the highest genetic diversity value and KY population had the lowest genetic diversity value. The distance between CW and CF populations was the farthest, which was possibly resulted from the farthest distance of Weihai of Shandong and Fujian of China compared with the geographical distance between other locations of populations. The subpopulation differentiation value （G.,） is 0. 356 5, showing a certain extent of differentiation among the four geographical populations. AFLP technology was confirmed to be an effective tool to assess within- and among-population genetic diversity of Japanese flounder. The present survey provided significant insights for research in the Japanese flounder breeding program.

Plant diversity, population structure, and regeneration status in disturbed tropical forests in Assam, northeast India

We investigated the plant population structure and the phy- tosociological and regeneration status in two disturbed tropical forests in Assam Province, the Hojai Reserve Forest and Kumorakata Reserve Forest. A total of 166 species （80 trees, 20 shrubs and 66 herbs） of 136 genera and 63 families were recorded in both study sites. The disturbance index at the two sites, Kumorakata Reserve Forest and Hojai Reserve Forest, were recorded at 11.4% and 3.70% respectively. Reverse J-shaped population curve and exploitation of tree species in higher girth classes were recorded at both study sites. In the girth classes （10-30 cm, 30-60 cm, 60-90 cm and 90-120 cm in size） the percentage of cut stump density was higher than the percentage of individual living trees. The 18% （Kumorakata Reserve Forest） and 7% （Hojai Reserve Forest） spe- cies were recorded as not regenerating. Illegal felling and over-exploitation of forest resources may lead to species-specific changes in the population structure and can alter the future structure and composi- tion of the forests.

ISSR Analysis on Genetic Diversity of the 34 Populations of Oryza meyeriana Distributing in Yunnan Province,China

The genetic diversity of the 34 populations of wild rice Oryza meyeriana Baill. distributed in Yunnan Province, China was analyzed using 13 inter-simple sequence repeat （ISSR） markers. A total of 168 bands were amplified, of which 135 polymorphic bands were discovered and the percentage of polymorphic bands （PPB） was 80.36%. A genetic diversity was revealed as Nei＇s gene diversity （H） = 0.2666 and Shannon information index （I） = 0.4028 at population level. The 34 populations were divided into different groups based on administrative regions, latitude and longitudes, river areas, altitudes of their origins, and their indexes such as Na （number of alleles）, Ne （effective number of alleles）, H, I and PPB were calculated. Richer genetic diversity was found in the wild rice populations distributed in Simao Prefecture than that in Lingcang Prefecture or Xishuangbanna Prefecture whereas the least genetic diversity was in Baoshan Prefecture or Dehong Prefecture. Rich genetic diversity was also discovered in the wild rice populations originated from higher than 710 m altitude around the middle and lower reaches of the Lancang River belonging to the Pacific Ocean drainage system. The 34 populations could be classified into two groups, one group covered the wild rice distributing in Simao Prefecture only while the other group covered ones in Lingcang, Xishuangbanna and Dehong Prefectures. The issue on how to effectively conserve the wild rice germplasm was discussed.

Genetic Diversity of Natural Myrica rubra Sieb.et Zucc Populations in Guangxi Revealed by ISSR Markers

The present study was conducted to assess the molecular characterization and genetic diversity amongst natural populations of Myrica rubra in Guangxi Zhuang Autonomous Region, China, thus to provide scientific evidence for germplasm conservation and exploitation. Using ISSR （inter-simple sequence repeats） markers, the level of genetic variation and the molecular characterization of 10 natural populations of M. rubra, originated from Guangxi Zhuang Autonomous Region in China, were performed. Based on 11 primers, 123 clear and reproducible DNA fragments were generated, of which 95 （77.24%） were polymorphic. The average value of Nei＇s gene diversity （He） was 0.268. The coefficient of genetic differentiation （Gst） was 0.341, revealing that 34.1% of the total molecular variance existed among populations. The Mantel statistical testing showed that the genetic distance was correlated to the geographic distance, but the correlation was not significant. Ten populations were divided into two big clusters according to unweighted pair group method with arithmetic mean （UPGMA） analysis. One consisted of populations of Rongxian （RX）, Hepu （HP）, Liangqing （LQ）, Marshan （MS）, Lingshan （LS） and Shansi （SS）, which originated from the southern Guangxi, while the other was composed of Guanyang （GY） and Lingui （LG） populations of northern Guangxi, Huanjiang （HJ） populations of northwestern Guangxi and Shanglin （SL） populations of southern Guangxi. The level of genetic variation in wild M. rubra population distributed in Guangxi is high. Gene drift within the population was responsible for genetic variation in wild M. rubra in Guangxi, and the effect of the genetic flow among inter-populations was not significant. Classification of wild M. rubra populations was correlated to climate and environment. The molecular characterization and diversity assessment of M. rubra is of immense value for planning conservation of its genetic resources and their exploitation for further studies.

Genetic diversity and structure of Rhododendron meddianum,a plant species with extremely small populations

Rhododendron meddianum is a critically endangered species with important ornamental value and is also a plant species with extremely small populations.In this study,we used double digest restriction-siteassociated DNA sequencing(ddRAD)technology to assess the genetic diversity,genetic structure and demographic history of the three extant populations of R.meddianum.Analysis of SNPs indicated that R.meddianum populations have a high genetic diversity(p?0.0772±0.0024,HE?0.0742±0.002).Both FST values(0.1582e0.2388)and AMOVA showed a moderate genetic differentiation among the R.meddianum populations.Meanwhile,STRUCTURE,PCoA and NJ trees indicated that the R.meddianum samples were clustered into three distinct genetic groups.Using the stairway plot,we found that R.meddianum underwent a population bottleneck about 70,000 years ago.Furthermore,demographic models of R.meddianum and its relative,Rhododendron cyanocarpum,revealed that these species diverged about 3.05(2.21e5.03)million years ago.This divergence may have been caused by environmental changes that occurred after the late Pliocene,e.g.,the Asian winter monsoon intensified,leading to a drier climate.Based on these findings,we recommend that R.meddianum be conserved through in situ,ex situ approaches and that its seeds be collected for germplasm.

Analysis of Genetic Diversity and Population Structure of Maize Landraces from the South Maize Region of China

Understanding genetic diversity and population structure of landraces is important in utilization of these germplasm in breeding programs. In the present study, a total of 143 core maize landraces from the South Maize Region （SR） of China, which can represent the general profile of the genetic diversity in the landraces germplasm of SR, were genotyped by 54 DNA microsatellite markers. Totally, 517 alleles （ranging from 4 to 22） were detected among these landraces, with an average of 9.57 alleles per locus. The total gene diversity of these core landraces was 0.61, suggesting a rather higher level of genetic diversity. Analysis of population structure based on Bayesian method obtained the samilar result as the phylogeny neighbor-joining （N J） method. The results indicated that the whole set of 143 core landraces could be clustered into two distinct groups. All landraces from Guangdong, Hainan, and 15 landraces from Jiangxi were clustered into group 1, while those from the other regions of SR formed the group 2. The results from the analysis of genetic diversity showed that both of groups possessed a similar gene diversity, but group 1 possessed relatively lower mean alleles per locus （6.63） and distinct alleles （91） than group 2 （7.94 and 110, respectively）. The relatively high richness of total alleles and distinct alleles preserved in the core landraces from SR suggested that all these germplasm could be useful resources in germplasm enhancement and maize breeding in China.

Genetic diversity and phylogenetic relationships between and within wild Pistacia species populations and implications for its conservation

Although cultivation and utilization of Pistacia are fully exploited, the evolutionary history of the Pistacia genus and the relationships among the species and accessions is still not well understood. The aim of this study was to analyze random amplified polymorphic DNA（RAPD） in a total of 50 accessions of wild pistachio species, which included five populations Pistacia vera, Pistacia khinjuk,Pistacia atlantica, Pistacia mutica, and Pistacia eurycarpa.High levels of genetic diversity were detected within wild pistachio accessions, as revealed by using the unweighted pair-group method with arithmetic averaging and supported via analysis of molecular variance. The objectives of this investigation were to estimate marker indices, polymorphic information contents（PICs）, and genetic similarities（GS）for RAPD markers; assess the genetic diversity of Pistacia species, using GS estimated from RAPD fingerprints and molecular characterization; and facilitate the use of markers in inter-specific introgression and cultivar improvement.Out of the 149 polymerase chain reaction fragments that were scored, 146（97.98 %） were polymorphic. Genetic similarities ranged from 0.3 to 0.86 %, marker indices ranged from 2.98 to 17.74 %, and PICs ranged from 0.80 to0.99 %. Our results provided great molecular identification of all assayed genotypes, which have shown that there is large quantity of genetic diversity among the pistachio accessions. This finding might render striking information in breeding management strategies for genetic conservation and cultivar development.

Genetic diversity and population structure of 288 potato(Solanum tuberosum L.) germplasms revealed by SSR and AFLP markers

Potato （Solanum tuberosum L.） is an important staple food and economic crop in many countries. China has led world potato production in recent years. To understand the genetic diversity of potato germplasms and to enrich the current gene pool for potato improvement, we made a global collection consisted of 288 potato germplasms from eight countries and the International Potato Center （CIP）. Using SSR and AFLP techniques, we evaluated the genetic diversity and population structure of these 288 potato accessions. A total of 190 alleles on 20 SSR loci were detected and all of the SSR alleles were polymorphic among these potato germplasms with an average of 9.5 alleles per SSR locus ranging from 2 to 23. The effective number of alleles per locus （Ne＊）, Nei＇s genetic diversity （H＊）, and Shannon＇s information index （I＊） was from （0.1709＋0.3698） to （1.6166＋0.3414）, （0.076＋0.1388） to （0.3812＋0.1886）, and （0.1324＋0.1970） to （0.5347＋0.1440）, respec- tively, and the mean polymorphic information content （PIC） value was 0.7312. A total of 988 AFLP alleles were detected by 10 AFLP primer combinations with 983 polymorphic alleles, and 99.49% alleles was polymorphic with an average of 98.3 polymorphic alleles per primer combination ranging from 91 to 116. The values of Ne＊, H＊ and/＊ were from （1.5162＋0.311 ） to （1.6423＋0.3278）, （0.3114＋0.145） to （0.3675＋0.1121）, and （0.4761＋0.1792） to （0.547＋0.1322）, respectively, and the average PIC value was 0.9871. Bayesian analysis discriminated the accessions into seven subgroup and an admix group. The majority of accessions from CIP and China were assigned into SG1, SG5, SG6, SG7 and admix group. Accessions in SG3 were mainly from CIP and two small groups SG2 and SG4 were mainly from northeastern China. In general, the results obtained from Bayesian statistical analysis, cluster analysis and principal coordinate analysis consistently revealed the lack of geographical differentiation among country-wide collections, indicating germplasm introduction was common for the countries out of potato origin center. The poiymorphic markers and the differentiate genetic lineages found in this study provide useful information for potato improvement and conservation programs.