Development of microsatellite markers and their utilization in genetic diversity analysis of cultivated and wild populations of the mud carp (Cirrhina molitorella)

Microsatellite markers have been increasingly used in genetic studies on fishery species because of their high applicability in selective breeding programs. Here we reported the development of microsatellite markers and their utilization in mud carp （Cirrhina molitorella）. An （CA）15 enriched library has been constructed for mud carp, using the magnetic beads enrichment procedure. Sequence analysis of 60 randomly picked positive colonies indicate that 56 （93.3%） of the colonies contain microsatellites. Microsatellite polymorphism was assessed using 10 mud carp individuals, and 12 microsatellite loci turned out to be polymorphic. We utilized these loci to study the genetic diversity of a wild population （WM） and a cultured population （CM） of the mud carp. A total of 109 alleles were detected with an average of 9.08 alleles per locus. The mean value of the observed heterozygosity of WM and CM was 0.6361 and 0.6417, respectively, and significant decrease of genetic diversity in CM was not observed. The genetic distance between the two populations was 0.1546 and the value of Gsr was 0.0473. This showed that there existed a slight genetic differentiation between WM and CM.

Assessment of Genetic Diversity of Drought Tolerant and Susceptible Rice Genotypes Using Microsatellite Markers

The introgression of wild chromosomal segments into popular rice varieties is one of the potential approaches for developing varieties for drought stress condition. Sixteen genotypes, including nine indica, two tropical japonica and five chromosome segments substitution lines (CSSLs) with different levels of tolerance/susceptibility to drought stress, were selected for diversity study. Sixty-three microsatellite markers were utilized for assessing genetic diversity. A total of 95 alleles were amplified, and out of them, 60 were polymorphic. Six unique alleles, amplified by the microsatellite loci RM276, RM472, RM488, RM537, RM541 and RM28089, were identified in six genotypes, namely FR13A, Brahamanakhi, RUF44, Swarna-sub1, Brahamanakhi and Satyabhama. The highest genetic similarity was found among CSSLs. Polymorphism information content (PIC) value varied from 0 to 1.00 with an average of 0.66 per locus. Twenty-eight microsatellites were found to be polymorphic, which could be used in marker-assisted selection programme. All the sixteen genotypes were grouped into two major clusters at genetic similarity of 0.64. In the cluster I, five CSSLs identified as diverse genotypes had wild ancestor segments responsible for drought tolerance, and hence they could be utilized as potential donors. The popular Indian varieties, Swarna-sub1 and IR64-sub1, could be used as recurrent parents in the future breeding program for developing varieties for abiotic stresses such as submergence and drought.

Genetic Diversity Estimates of <i>Santalum album</i>L. through Microsatellite Markers: Implications on Conservation

Sandalwood (Santalum album L.) is the second most expensive wood in the world. There are approximately 16 species of sandalwood (S. album, S. spicatum, S. austrocaledonicum, S. yasi, S. lanceolatum, S. ellipticum, S. macgregorii, S. insulare) occurring naturally throughout Australia, India, Indonesia, Papua New Guinea and the islands of the South Pacific. In India, S. album is found all over the country, with over 90% of the area in Karnataka, Tamil Nadu, Kerala, Andhra Pradesh and Telangana state. It is highly economic tropical tree species because of its scented heartwood and heartwood oil. Several causes have been attributed to the depletion of sandalwood population mainly amongst which theft is causing negative effect on the quality of species by constant removal of superior clones. The aim of this study was to determine the genetic diversity of S. album. For this, 177 genotypes of S. album from 14 populations of three states (Karnataka, Telangana state and Kerala) in southern India were selected. The genetic diversity and genetic structure were characterized through 25 SSR markers developed by cross amplification of different species of Sandalwood. Under this study, following genetic diversity parameters were estimated at individual level and population level;Number of alleles (Na) 9.107, Effective number of alleles (Ne) 7.56, Observed heterozygosity (Ho) 0.187, Expected heterozygosity (He) 0.861, Shannon information index (I) 2.03, F statistics 0.89, Polymorphic information content (PIC) 0.87 and Gene flow (Nm) 4.98. The estimates of gene flow among the populations of Kodada Telangana (Nm = 15.109);IWST Karnataka (Nm = 13.62) than across other geographical populations (Nm = 9.40). Analysis of molecular variance (AMOVA) revealed that 3% of the total variation was due to differences among populations and 97% due to differences within the populations. The genetic differentiation among populations (FST) 0.012 at p < 0.001 was significant. Structure clustering at Ks = 3 highlighted three distinct groups with the inferred clusters i. 0.369, ii. 0.304, iii. 0.327. Structure analysis revealed that genetic structure of Kerala and Karnataka and Telangana populations were admixtures and classified in three groups. In addition, all the accessions were clearly divided into three major clusters by UPGMA dendrogram which could be further divided into five sub groups. Principal component analysis (PCA) results showed the combined variation 82.2% of these markers. This study highlights the knowledge of genetic variation in sandalwood across the herd population of sandalwood in India. The highest range of polymorphism was detected with SSR markers developed from Osyris lanceolata compared to Santalum. austrocaledonicum, Santalum. insulare and Santalum. spicatum. This study would help in conservation of the Sandalwood populations with high profile of genetic diversity and selection of clones for genetic improvement program.

Inbreeding and genetic diversity analysis in a hatchery release population and clones of Rhopilema esculentum based on microsatellite markers

Ten microsatellite markers were used to analyze the levels of genetic diversity and inbreeding in a hatchery release population of Rhopilema esculentum Kishinouye(Scyphozoa: Rhizostomatidae). A total of 85 alleles were detected in 600 individuals. Within-population levels of observed( H o) and expected( H e) heterozygosity ranged from 0.152 to 0.839(mean=0.464) and from 0.235 to 0.821(mean=0.618), respectively. The polymorphism information content(PIC) of each marker ranged from 0.207 to 0.795 with an average of 0.580, indicating that the hatchery population maintained a high level of genetic diversity. Inbreeding levels were estimated in the hatchery population and the inbreeding coefficient was 0.203. This result revealed that a certain level of inbreeding occurred within the population. Meanwhile, we also determined genetic diversity at the clone level. Several polyps from the same scyphistomae were genotyped at the ten microsatellite loci and there was virtually no difference in their genotypes. Furthermore, we calculated the probabilities of exclusion. When both parents were known, the average exclusion probability of ten loci was 99.99%. Our data suggest that the ten microsatellite markers can not only be used to analyze the identity of individuals but they can also be applied to parentage identification. Our research provides a theoretical basis and technical support for genetic diversity detection and reasonable selection of R. esculentum hatchery populations. These findings support the use of releasing studies and conservation of R. esculentum germplasm resources.

Discordant patterns of genetic variation between mitochondrial and microsatellite markers in Acanthogobius ommaturus across the coastal areas of China

Acanthogobius ommaturus, which belongs to the family Gobiidae, is a euryhaline and demersal fish that is widely distributed in the coastal areas, harbors, and estuaries of China, D. P. R. Korea and Japan. In this study, the genetic diversity and genetic structure of five geographical populations of A. ommaturus was assessed using the mitochondrial hypervariable region gene and microsatellite markers. The results of the two genetic markers indicated that the A. ommaturus populations had a high level of genetic diversity. The mitochondrial marker detected weak genetic differentiation among populations, and the Neighbor-Joining tree showed that there was no obvious pedigree branches and geographic structure as well. However, population of Zhoushan showed significant genetic differentiation with other populations by microsatellite markers. The population of A.ommaturus has not experienced bottleneck effect recently. We speculated that the Pleistocene climate change and juvenile fish dispersal played an important role in the population differentiation of A. ommaturus.

Intra-breed Genetic Variation of Fragrance Pigs Detected by Microsatellite Markers

[Objective] The genetic background of four types of fragrance pigs was studied using microsatellite molecular markers,in order to fully understand the genetic resources of miniature pigs in China.[Method] Using 27 pairs of microsatellite loci jointly recommended by Food and Agricultural Organization（FAO）and International Society for Animal Genetics（ISAG）,we detected the genotypes of 200 fragrance individuals belonging to four types（Jiuyang fragrance pig,Jianbai fragrance pig,Congjiang fragrance pig and Huanjiang fragrance pig）,and analyzed their Inter-and intra-breed genetic variations.[Result]The 23 loci detected in the test were high polymorphic;the mean heterozygosity（H） of Jiuyang fragrance pig,Jianbai fragrance pig,Congjiang fragrance pig and Huanjiang fragrance pig were 0.683 6,0.667 9,0.697 3 and 0.702 2,and their mean polymorphism information contents（PIC） were 0.6263,0.6063,0.6420 and 0.6415,respectively.[Conclusion]Four types of fragrance pigs detected in the test all had high intra-breed genetic variability.

Morphometric analysis and fluorescent microsatellite markers to evaluate the genetic diversity of five populations of Penaeus japonicus in China

To understand the current status of germplasm resources of Penaeus japonicus,in this study,genetic diversity was analyzed based on morphometric analysis and fluorescent microsatellite markers.For morphometric analysis,the cumulative ratios of the PC1 and PC2(85.90%)were greater than 75%,which can explain the morphological variation among populations.For microsatellite analysis,the allele number in 10 microsatellite loci ranged from 27 to 53,and the effective allele number ranged from 21 to 42.The observed heterozygosity ranged from 0.463 to 0.983,whereas expected heterozygosity ranged from 0.932 to 0.966,and the average polymorphism information content was 0.947,which indicated a high level of genetic diversity.The unbiased genetic distance among populations ranged from 0.230 to 0.431,and the genetic similarity coefficient ranged from 0.654 to 0.782.Analysis of molecular variance(AMOVA)showed that the genetic variation within individuals was the main source of variation,accounting for 88.55%,and only 1.49%of the genetic variation came from among populations.

Microsatellite Marker Based Assessment of Genetic Diversity among Cultivars, Landraces and Wild Relatives in Rice

India being the primary center of origin for rice had a very large treasure of local land races, most of which are out of cultivation today. The exact genetic potential and their differences from commercial varieties and

Genetic diversity in Chinese modern wheat varieties revealed by microsatellite markers

Genetic diversity of 1680 modern varieties in Chinese candidate core collections was analyzed at 78 SSR loci by fluorescence detection system. A total of 1336 alleles were detected, of which 1253 alleles could be annotated into 71 loci. For these 71 loci, the alleles ranged from 4 to 44 with an average of 17.6, and the PIC values changed from 0.19 to 0.89 with an average of 0.69. (1) In the three genomes of wheat, the average genetic richness was B＞A＞D, and the genetic diversity indexes were B＞D＞A. (2) Among the seven homoeologous groups, the average genetic richness was 2=7＞3＞4＞6＞5＞1, and the genetic diversity indexes were 7＞3＞2＞4＞6＞5＞1. As a whole, group 7 possessed the highest genetic diversity, while groups 1 and 5 were the lowest. (3) In the 21 wheat chromosomes, 7A, 3B and 2D possessed much higher genetic diversity, while 2A, 1B, 4D, 5D and 1D were the lowest. (4) The highest average genetic diversity index existed in varieties bred in the 1950s, and then it declined continually. However, the change tendency of genetic diversity among decades was not greatly sharp. This was further illustrated by changes of the average genetic distance between varieties. In the 1950s it was the largest (0.731). Since the 1960s, it has decreased gradually (0.711, 0.706, 0.696, 0.695). The genetic base of modern varieties is becoming narrower and narrower. This should be given enough attention by breeders and policy makers.

Evaluation of genetic diversity in Chinese indigenous chicken breeds using microsatellite markers

China is rich in chicken genetic resources, and many indigenous breeds can be found throughout the country. Due to poor productive ability, some of them are threatened by the commercial varieties from domestic and foreign breeding companies. In a large-scale investigation into the current status of Chinese poultry genetic resources, 78 indigenous chicken breeds were surveyed and their blood samples collected. The genomes of these chickens were screened using microsatellite analysis. A total of 2740 individuals were genotyped for 27 microsatellite markers on 13 chromosomes. The number of alleles of the 27 markers ranged from 6 to 51 per locus with a mean of 18.74. Heterozy-gosity (H) values of the 78 chicken breeds were all more than 0.5. The average H value (0.622) and polymorphism information content (PIC, 0.573) of these breeds suggested that the Chinese indige-nous chickens possessed more genetic diversity than that reported in many other countries. The fixa-tion coefficients of subpopulations within the total population (FST) for the 27 loci varied from 0.065 (LEI0166) to 0.209 (MCW0078), with a mean of 0.106. For all detected microsatellite loci, only one (LEI0194) deviated from Hardy-Weinberg equilibrium (HWE) across all the populations. As genetic drift or non-random mating can occur in small populations, breeds kept on conservation farms such as Langshan chicken generally had lower H values, while those kept on large populations within con-servation regions possessed higher polymorphisms. The high genetic diversity in Chinese indigenous breeds is in agreement with great phenotypic variation of these breeds. Using Nei’s genetic distance and the Neighbor-Joining method, the indigenous Chinese chickens were classified into six categories that were generally consistent with their geographic distributions. The molecular information of genetic diversity will play an important role in conservation, supervision, and utilization of the chicken re-sources.

Study on Genetic Diversity of Some Cattle Breeds

Four microsatellites IDG VA-11, IDG VA-27, IDG VA-44 and IDG VA-46 were used to analyze genetic diversity of five cattle breeds. The average gene diversity of the four loci was 0.57, of which IDG VA-11 was 0.66. Genetic diversity of five cattle breeds was 0. 57, Nanyang was the highest 0. 66, Yanbian and Korea cattle were 0.51 and 0. 53, respectively. The fact that the observed diversity was lower than expected in Simmental and Piemontese crossbred showed existing selection and inbreeding impacts. The gene flow between Yanbian and Korea cattle, and that between Simmental and Piemontese crossbred were as high as 23. 79 and 7.15 for each pairs of them, which showed their closer origins.

Genetic diversity and a population structure analysis of accessions in the Chinese cowpea [Vigna unguiculata(L.)Walp.]germplasm collection

Cowpea(Vigna imguicuiata) is an important legume crop with diverse uses. The species is presently a minor crop, and evaluation of its genetic diversity has been very limited. In this study, a total of 200 genic and 100 genomic simple sequence repeat(SSR) markers were developed from cowpea unigene and genome sequences, respectively. Among them, 27 genic and 27 genomic SSR markers were polymorphic and were used for assessment of genetic diversity and population structure in 105 selected cowpea accessions. A total of 155 alleles and 2.9 alleles per marker were identified, and the average polymorphic information content(PIC) value was 0.3615. The average PIC of genomic SSRs(0.3996) was higher than that of genic SSRs(0.3235), and most of the polymorphic genomic SSRs were composed of di-and trinucleotide repeats(51.9% and 37.0% of all loci, respectively). The low level of detected genetic diversity may be attributed to a severe genetic bottleneck that occurred during the cowpea domestication process. The accessions were classified by structure and cluster analysis into four subgroups that correlated well with their geographic origins or collection sites. The classification results were also consistent with the results from principal coordinate analysis and can be used as a guide during future germplasm collection and selection of accessions as breeding materials for cultivar improvement. The newly developed genic and genomic SSR markers described in this study will be valuable genomic resources for the assessment of genetic diversity, population structure, evaluation of germplasm accessions, construction of genetic maps, identification of genes of interest,and application of marker-assisted selection in cowpea breeding programs.

Genetic Structure and Diversity of Parental Cultivars Involved in China Mainland Sugarcane Breeding Programs as Inferred from DNA Microsatellites

To understand genetic structure and diversity of parental cultivars involved in China Mainland sugarcane breeding programs, 92 elite parents and 4 wild relatives were genotyped with 18 microsatellite DNA markers. The genetic similarity （GS） values among the cultivars ranged from 0.346 to 0.960 with an average of 0.533. Among the introduced cultivars, India accessions had the closest genetic distance to China Mainland accessions （0.447）, while Australia accessions have the furthest distance （0.503）. A comparison of allelic diversity among geographical origins showed that there were 22 China Mainland specific alleles, of which 28% were derived from native S. spontaneaum germplasm in China. Model-based genetic structure, clustering, and principal components analyses consistently revealed there were five groups within the 96 accessions. Groups 1, 2, 4, and 5 consisted of all cultivars and group 3 only contained wild germplasm. Group 2 was characterized as the Introduction group with 46 cultivars predominantly introduced from Australia, Taiwan of China, India, and USA. Groups 1, 4, and 5 consisted of cultivars mostly originated from China Mainland, defined as the Complex group, Yacheng lines group, and F134/CP72-1210 group, respectively, upon their pedigree. By understanding the genetic relationships among the parental cultivars, breeders can gain a rational basis for expanding the gene pool and select the best parental accessions for crossing.

海南金鲳人工养殖群体遗传多样性与遗传结构的微卫星分析

为评估海南省金鲳(Trachinotus blochii)人工养殖群体的种质资源背景及群体遗传结构,研究利用16对微卫星标记对采集自海南东方基地(晨海群体, CH)、陵水基地(青利群体, QL)、三亚基地(蓝粮群体, LL)共3家繁育公司的210尾金鲳进行了群体遗传学分析。结果显示, 16个微卫星标记在3个群体中共检测到251个等位基因(N_(a)),平均观测杂合度(H_(o))、平均期望杂合度(He)及平均多态信息含量(PIC)分别为0.630、0.714及0.679,各位点的基因流(N_(m))平均为5.217。其中QL群体具有较高的遗传多态性。群体间的Nei’s遗传分化系数(F_(st))介于0.017—0.038, AMOVA结果显示个体间的遗传变异占总变异的87%。STRUCTURE遗传聚类分析将3个群体分为两个亚群(K=2), QL与LL构成遗传亚群I,而CH构成遗传亚群II。UPGMA聚类分析结果与STRUCTURE基本一致,并进一步揭示了CH群体与QL、LL群体之间在遗传结构上的差异。综上, 3个不同来源的海南省金鲳养殖群体尚保持较高的遗传多样性,且存在一定的遗传结构差异。研究结果可为金鲳种质资源的评价与利用提供一定的数据支撑。

基于九个微卫星标记的核桃举肢蛾地理种群的遗传多样性分析

【目的】核桃举肢蛾Atrijuglans hetaohei是核桃Juglans regia上的一种重要蛀果性害虫,在我国北京、山东、山西、陕西、四川等核桃种植产业区普遍发生,严重影响核桃的产量和商品价值,造成严重的经济损失。本研究旨在明确核桃举肢蛾地理种群遗传分化和地理分布特点,阐明其不同地理种群间的遗传结构,了解其种群扩散规律,为核桃举肢蛾的防控提供理论指导。【方法】基于核桃举肢蛾转录组测序结果,使用聚丙烯酰胺凝胶电泳和毛细管电泳分型方法,利用筛选的多态性微卫星位点对我国8个省/市(北京、河北、河南、山东、山西、陕西、甘肃和四川)的16个地理种群共319头核桃举肢蛾样本进行种群遗传多样性分析,使用STRUCTURE和BAPS软件分析其种群遗传结构,并对影响其地理分布的因素进行探讨。【结果】核桃举肢蛾9个SSR位点具有较高的多态性,且多数位点未偏离哈迪-温伯格平衡。核桃举肢蛾各地理种群遗传多样性中等偏低(有效等位基因数Ne为1.334~1.824,期望杂合度He为0.203~0.342),种群间遗传分化较小(遗传分化系数F_(ST)<0.142),种群间基因流差异较大(Nm为1.518~23.800)。核桃举肢蛾地理种群间遗传分化程度与地理距离间有显著相关性(R^(2)=0.226)。16个核桃举肢蛾地理种群可分为两支,即东部和西部种群。AMOVA分析表明,核桃举肢蛾种群间遗传变异较小,且种群变异主要来源于种群内;种群内的遗传分化系数FCT值在0.03941~0.06449之间,表明地理阻隔和气候差异不是影响核桃举肢种群遗传结构和地理分布格局的主要因素。【结论】核桃举肢蛾地理种群遗传多样性中等偏低,不同地理种群间存在较低水平的遗传分化和差异较大的基因流。鉴于核桃举肢蛾特殊的生活史和独特的生物学特性,结合种群遗传结构分析结果,我们推测河流对核桃举肢蛾地理种群基因流的阻碍作用强于山川,而作为主要经济果树害虫,人类活动可能是干扰核桃举肢蛾种群地理分布的最主要因素。

中国虎纹蛙多碱基重复微卫星位点的多态性

[目的]筛选出中国虎纹蛙高质量多态性的微卫星标记,用于该物种的鉴定以及遗传多样性、种群结构、遗传连锁图谱分析。[方法]利用新一代测序技术,从中国虎纹蛙部分基因组中筛选出33个三核苷酸重复、42个四核苷酸重复和1个五核苷酸重复微卫星位点,共76个多碱基重复微卫星位点。所有位点对浙江丽水学院两栖爬行动物实验室人工饲养的种群(n=30)进行了扩增和基因型分析。[结果]每个位点观察到的等位基因数和多态信息含量(PIC)的平均值分别为4个(2~7个)和0.514(0.164~0.822),观测杂合度(H_(O))和期望杂合度(H_(E))分别为0.00~0.97和0.18~0.82。有2个位点(THC141和THC377)显著偏离哈迪温伯格平衡,在11个位点中发现了显著的连锁不平衡。[结论]这些新筛选的多态性微卫星标记有助于进一步研究中国虎纹蛙的遗传多样性和开展遗传育种,为制定有效的保护策略和开展分子辅助选择提供依据。

基于简化基因组测序宽鳍鱲的微卫星分子标记及遗传多样性分析

【目的】建立基于简化基因组测序(2b-RAD)宽鳍鱲(Zacco platypus)的微卫星分子标记,并进行遗传多样性分析,为有效开展宽鳍鱲品种间遗传多样性分析和分子育种,挖掘和利用宽鳍鱲种质资源提供参考。【方法】利用限制性内切酶EcoRⅠ打断基因组DNA,每个样本分别进行物理打碎,选取300~700 bp插入片段文库,利用Illumina HiSeq PE150测序平台进行双末端(Paired-End)测序获得海量遗传多态性标签序列。【结果】2b-RAD筛选宽鳍鱲的微卫星位点得到两端各留100 bp作为引物的SSR数量为41018个,带有引物片段的SSR数量为1522个,片段引物的设计率为37.1%,构建的文库质量较高,测序深度达高准确度下的分型标准。在筛选的64个微卫星位点中,有14个位点(21.88%)具有多态性,由于存在无效等位基因,有3个位点(Zpla08、Zpla09和Zpla10)显著偏离Hardy-Weinberg平衡(P<0.05),因此选用其中的11个微卫星位点分析宽鳍鱲群体遗传多样性。基于11个微卫星DNA位点的分析表明,宽鳍鱲7个群体的平均等位基因数(N_(A))为3.66,平均Shannon;s信息指数(I)为0.689,平均观测杂合度(H_(O))为0.315,平均期望杂合度(H_(E))为0.354,平均多态信息含量(PIC)为0.409。【结论】基于简化基因组测序(2b-RAD)开发宽鳍鱲的微卫星分子标记可用于评估野生宽鳍鱲种群的遗传多样性、遗传结构和物种鉴定。宽鳍鱲基因组DNA 14个微卫星位点中有11个微卫星位点具有中高多态性,3个位点(Zpla08、Zpla09、Zpla10)偏离Hardy-Weinberg平衡,在群体遗传研究中应慎用。

Morphological characteristics and genetic differentiation of Lutraria maxima in coast waters off southeast China

To explore genetic diversity and estimate the genetic differences among populations of Lutraria maxima in the coastal waters off south to southeast China,the morphology of the species of five different geographical populations(Beihai,Weizhou Island,Zhanjiang,Xiamen,and Fuzhou)in Guangxi,Guangdong,and Fujian provinces was studied statistically in combination with the microsatellite markers.As revealed by morphological principal component analysis(PCA),the cumulative contribution rate of the first three principal components was 72.596%.The discrimination accuracy ranged from 47.5%to 80.0%,and the scatter plots of principal component and discriminant analysis were consistent in overall,showing that the Xiamen and Fuzhou populations were overlapped obviously.For microsatellite markers,10 pairs of polymorphic primers were obtained by high-throughput transcriptome sequencing,and used for genetic diversity analysis.It was showed that the average number of alleles and eff ective alleles observed in each population ranged from 8.100 to 10.900,and from 3.497 to 4.228,respectively.The average observed heterozygosity(H_(o))and expected heterozygosity(H_(e))in the five populations ranged from 0.541 to 0.615,and from 0.642 to 0.733,respectively.The genetic distance(DA)ranged from 0.078 to 0.523,and the population genetic differentiation index(F_(ST))ranged from 0.027 to 0.139.The unweighted pair-population method with arithmetic means(UPGMA)and structure analysis showed that the five populations could be divided into two main clusters,the Beibu Gulf group(Beihai and Weizhou Island)and the Southeast China Sea group(Zhanjiang,Xiamen,and Fuzhou),suggesting that L.maxima has been separated geographically by the barrier of the Leizhou Peninsula into two groups in evolution,which provided us with a scientific clue to better protect the bioresource and establish an appropriate fishery management stocks for L.maxima populations in south China.

长牡蛎(Crassostrea gigas)野生与选育群体的微卫星遗传多样性分析

为了评估长牡蛎(Crassostrea gigas)2个壳长性状(掌心形)快速生长选育群体(LY2-K4、LY2-K7)、1个壳高性状(速生型)快速生长选育群体(LY2-K11)和6个野生群体(QHD、LS、HD、ZH、WD、KTD)的遗传多样性和遗传结构,用21对多态性丰富的微卫星引物对9个长牡蛎群体的269个个体进行了遗传分析。结果显示:21个微卫星位点共检测出了460个等位基因(Na),平均等位基因数为21.905;21个微卫星位点的多态信息含量(PIC)均大于0.5,具有高度遗传多态性;选育群体LY2-K11的遗传多样性最低(Na=13,I=2.128,He=0.831,PIC=0.825),野生群体KTD的遗传多样性最高(Na=29,I=3.112,He=0.941,PIC=0.938);189个群体位点组合有66%偏离哈代-温伯格平衡,表明这些群体存在一定程度的杂合子缺失;9个群体间的遗传分化指数(F_(st))为0.012~0.064,处于较低的遗传分化水平;AMOVA分析显示遗传变异主要来自于个体内;PCoA分析结果与UPGMA聚类树一致,LY2-K11群体单独聚为一类,QHD和HD群体聚为一类,其他6个群体聚为一类。综上所述,长牡蛎3个选育群体和6个野生群体遗传多样性均较高,遗传分化水平较低;选育群体LY2-K11多样性略有下降,选育过程中应保证亲本的数量及质量,防止因近交衰退造成遗传多样性降低,苗种抗逆性变差。该结果将为长牡蛎新品种的选育和野生种质资源的保护提供科学指导。

Fine-scale analysis reveals a potential influence of forest management on the spatial genetic structure of Eremanthus erythropappus

Forest management may have significant effects on forest connectivity and natural population sizes.Harvesting old-growth single trees may also change natural patterns of genetic variation and spatial genetic structure.This study evaluated the impacts of forest management using a silvicultural system of seed trees on the genetic diversity and spatial genetic structure of Eremanthus erythropappus(DC.)MacLeish.A complete survey of 275 trees on four plots was undertaken out to compare the genetic variation of a managed stand with an unmanaged stand.We genotyped all adult and juvenile individuals 60 months after the management and compared the genetic diversity and the spatial genetic structure parameters.Genetic diversity was considered high because of an efficient gene flow between stands.There were no genetic differences between stands and no evidence of inbreeding.Genetic clustering identified a single population(K=1),indicating no genetic differentiation between managed and unmanaged stands.Adult and juvenile individuals of the unmanaged stand were more geographically structured than individuals from the managed one.There was a tendency of coancestry among juveniles at the first class of distance of the managed stand,suggesting a drift of genetic structure possibly caused by management.Understanding early responses to management on genetic diversity and stand structure is a first step to ensuring the effectiveness of conservation practices of tree species.The sustainability of forest management of E.erythropappus on genetic diversity,and more accurately,on spatial genetic structure needs evaluation over time to promote effective conservation of the population size and genetic variability.