我国陆地棉基础种质遗传多样性的SSR分子标记分析

利用398对BNL、JESPR、TMB等SSR引物,对不同亲本来源、不同选育时期、不同种植生态区的43份陆地棉基础种质进行了遗传多样性的SSR分子标记分析。扩增产物用8％的非变性聚丙烯酰胺凝胶检测,银染观察并照相。遗传多样性带型分析按位点多态信息量（PIC）,Shannon-weaver多样性指数（H^＋）等方法,利用NTSYSpc2．1软件计算品种间的遗传相似系数（Jaccard系数）,并用类平均法（UPGMA）进行聚类。结果表明所选择多态性引物分布在棉花基因组的第3、4、5、8、9、10、16、18、20、23号等染色体上,36对多态性引物在基础种质中扩增等位基因130个,其中多态性等位基因占80％,每个引物扩增等位基因2～8个,平均3．6个,PIC为0．278～0．865,平均0．62,基因型多样性（H^＋）为0．451～2．039,平均1．102,基础种质问SSR遗传相似系数平均为0．610,变幅为0．409～0．865,这说明所选基础种质基因组水平的多样性较丰富,变化范围大、代表性强。按品种不同选育时期来讲,第一、二、三期基础种质的SSR分子标记平均遗传相似系数分别是0．587、0．630、0．630,说明现代基础种质比早期基础种质在基因组水平的差异呈下降的趋势,可能是由于育种者偏重于使用优质高产性状的亲本品种,致使我国棉花的育种基础逐渐变窄。不同棉区基础种质SSR标记性状差异大,北部特早熟棉区基础种质间的SSR标记的多样性大于黄河、长江棉区,主要原因是长江、黄河棉区的育种过分强调高产、优质品种选育,品种间的差异变小;基础种质中的国内品种SSR相似系数（0．624）比引进品种（0.85）高,说明国内品种在遗传多样性上目前还没有超越国外品种。总之,我国棉花现代基础种质比早期基础种质的遗传多样性呈下降的趋势,黄河、长江主产棉区基础种质的遗传多样性还没有超过国外基础种质,品种间的遗传背景较为狭窄,还必须采用多种途径丰富我国棉花种质资源的遗传多样性。     

Characterization and development of EST-SSR markers to study the genetic diversity and populations analysis of Jerusalem artichoke (<Emphasis Type="Italic">Helianthus tuberosus</Emphasis> L.)

In recent years, Jerusalem artichoke has received widespread attention as a novel source of sugar, biofuel, and animal feed. Currently, only few gDNA-SSRs derived from sunflower were verified in the Jerusalem artichoke; therefore, it is particularly important to develop SSR primer markers that belonged to Jerusalem artichoke resources. Using EST data to develop EST-SSR markers is simple and effective. In order to understand the general characteristics of SSR markers in Jerusalem artichoke EST sequences and accelerate the use of SSR markers in Jerusalem artichoke research. This study used 40,370 sequenced unigene fragments and MISA software to identify SSR loci. The 48 pairs of EST-SSR primers assessed for the identification of 45 varieties of Jerusalem artichoke. Cluster, genetic diversity parameters and AMOVA analysis was conducted using the genetic similarity coefficient, revealing genetic differences between 48 genetic material. A total of 1204 SSR loci were identified with 13 different types of repeats, distributed among 1020 EST sequences, of which trinucleotide repeats were the most common, accounting for 38.21% of the total SSR loci. Among the 44 repeat motifs, AG/CT, AAG/CTT, and ATC/ATG motifs had the highest frequencies, accounting for 22.45, 14.71, and 7.84% of all motifs, respectively. From these sequences, 48 pairs of EST-SSR primers were designed, and 22 primer pairs for loci with high polymorphism were selected to analyze the genetic diversity of 45 Jerusalem artichoke germplasm sources. The results indicated that the variation range of the effective number of alleles for 22 primers ranged between 1.7502 and 4.5660. The Shannon’s information index ranged between 0.6200 and 1.6423. The variation range of PIC ranged between 0.3121 and 0.6662 with an average of 0.5184. Cluster analysis was conducted using the genetic similarity coefficient, revealing significant genetic differences between Asian and European genetic material. Cluster analysis revealed a relationship between the genotypes and geographic origins of the Jerusalem artichoke. The results of AMOVA as well as the genetic identity and genetic distance in the Jerusalem artichoke population showed that there presented certain genetic heterogeneity in Jerusalem artichoke genetic structure of 45 samples from seven different geographic populations. The Jerusalem artichoke EST-SSR marker system established in this study provides an effective molecular marker system for future research focused on Jerusalem artichoke genetic diversity and the breeding of new varieties.     

Genetic Diversity of Source Germplasm of Upland Cotton in China as Determined by SSR Marker Analysis

The genetic diversity of 43 sources of Upland cotton germplasm with different parental origins, breeding periods, and ecological growing areas in China were studied on the basis of simple sequence repeat (SSR) markers. A total of 130 gene alleles with 80% polymorphism were detected from 36 SSR primers. The number of alleles per primer ranged from two to eight with an average of 3.6. The polymorphism information content (PIC) range was 0.278-0.865, with an average of 0.62. The average genotype diversity index (H') was 1.102, the highest was 2.039 and the lowest was 0.451. The average coefficient of the genetic similarity of SSR markers among source germplasm was 0.610, ranging from 0.409 to 0.865. These indicated that the genetic diversity at the genomic level of the selected source germplasm was rich, and was representative of the diversity of the germplasms, in general. The diversity at the genome level of the base germplasm from the second and third breeding periods was decreased compared to that of the first period, indicating that the cotton genetic background in China became narrow gradually. The diversity of SSR markers among the base germplasm from early maturity cotton growing areas in the north was higher than those from the Huanghe and Yangtze growing areas. The molecular marker genetic similarity index of the domestic varieties was higher than that in the introduced varieties, which indicates that the genetic diversity in domestic cultivars was lower than that in the introduced varieties. This study gives an overview of the genetic diversity of the cotton germplasm base in China, and provides a guide for breeders to develop new cultivars efficiently.     

黑龙江省近年审定水稻品种基于SSR标记的遗传多样性分析

为评估黑龙江省水稻品种的遗传基础,利用24个用于水稻DNA指纹图谱构建的SSR标记以及其他均匀分布于水稻12条染色体的38个SSR标记,对黑龙江省近年审定的73个水稻常规稻品种进行遗传多样性分析。结果表明,在62个SSR标记位点中,共检测到142个等位基因,平均每个标记2.3个,多态性比率平均为71.0%,多态性频率变幅为0~0.775,平均值为0.246。供试品种间两两遗传相似系数的平均值为0.759,变幅为0.622~0.966,且96.4%的品种间遗传相似系数在0.66~0.86之间,表明供试的73个品种亲缘关系较近。通过SSR标记基因型聚类分析将这些品种划分为6个类群,与系谱分析趋势一致,类群间的差异主要表现在生育期和米质方面。综上所述,黑龙江省近年审定的水稻品种遗传基础狭窄,在育种中需要导入新的种质资源,加强种质资源创新,以期丰富水稻品种的遗传多样性,进一步提高水稻产量和抗性。     

Microsatellite analysis reveals a progressive widening of the genetic basis in the elite durum wheat germplasm

It has been argued that the level of genetic diversity in the modern durum wheat (Triticum turgidum L. var. durum) elite germplasm may have declined due to the high selection pressure applied in breeding programs. In this study, 58 accessions covering a wide spectrum of genetic diversity of the cultivated durum wheat gene pool were characterized with 70 microsatellite loci (or simple sequence repeats, SSRs). On average, SSRs detected 5.6 different allelic variants per locus, with a mean diversity index (DI) equal to 0.56, thus revealing a diversity content comparable to those previously observed with SSRs in other small-grain cereal gene pools. The mean genetic similarity value was equal to 0.44. A highly diagnostic SSR set has been identified. A high variation in allele size was detected among SSR loci, suggesting a different suitability of these loci for estimating genetic diversity. The B genome was characterized by an overall polymorphism significantly higher than that of the A genome. Genetic diversity is organised in well-distinct sub-groups identified by the corresponding foundation-genotypes. A large portion (92.7%) of the molecular variation detected within the group of 45 modern cvs was accounted for by SSR alleles tracing back to ten foundation-genotypes; among those, the most recent CIMMYT-derived founders were genetically distant from the old Mediterranean ones. On the other hand, rare alleles were abundant, suggesting that a large number of genetic introgressions contributed to the foundation of the well-diversified germplasm herein considered. The profiles of recently released varieties indicate that the level of genetic diversity present in the modern durum wheat germplasm has actually increased over time.Communicated by F. Salamini     

Identification of unique alleles and assessment of genetic diversity of rabi sorghum accessions using simple sequence repeat markers

Genetic diversity among 42 sorghum accessions representing landraces (19), advanced breeding lines (16), local cultivars (2) and release varieties (5) with 30 simple sequence repeat (SSR) markers revealed 7.6 mean number of alleles per locus showing 93.3% polymorphism and an average polymorphism information content of 0.78 which range from 0.22 (Xtxp12) and 0.91(Xtxp321). The average heterozygosity and effective number of alleles per locus were 0.8 and 6.65 respectively. Cluster analysis based on microsatellite allelic diversity clearly demarcated the accessions into ten clusters. A total of 24 unique alleles were obtained from seven SSR loci in 23 accessions in a size range of 110–380 bp; these unique alleles may serve as diagnostic tools for particular region of the genome of respective genotypes. Selected SSR markers from different linkage groups provided an accurate way of determining genetic diversity at the molecular level.     

Diversification of indigenous gene- pool by using exotic germplasm in lentil (Lens culinaris Medikus subsp. culinaris)

Genetic diversity was studied among 21 accessions of lentil using SSR markers and morphological traits in order to assess the diversification of Indian gene-pool of lentil through introgression of exotic genes and introduction of germplasm. Among these , 16 genotypes either had ‘Precoz’ gene, an Argentine line in their pedigree or genes from introduced lines from ICARDA. Sixty five SSR markers and eight phenotypic traits were used to analyse the level of genetic diversity in these genotypes. Forty three SSR markers (66 %) were polymorphic and generated a total of 177 alleles with an average of 4.1 alleles per SSR marker. Alleles per marker ranged from 2 to 6. The polymorphic information content ranged 0.33 to 0.80 with an average of 0.57, suggesting that SSR markers are highly polymorphic among the studied genotypes. Genetic dissimilarity based a dendrogram grouped these accessions into two main clusters (cluster I and cluster II) and it ranged 33 % to 71 %, suggesting high level of genetic diversity among the genotypes. First three components of PCA based morphological traits explained higher variance (95.6 %) compared to PCA components based on SSR markers (42.7 %) of total genetic variance. Thus, more diversity was observed for morphological traits and genotypes in each cluster and sub-cluster showed a range of variability for seed size, earliness, pods/plant and plant height. Molecular and phenotypic diversity analysis thus suggested that use of germplasm of exotic lines have diversified the genetic base of lentil germplasm in India. This diversified gene-pool will be very useful in the development of improved varieties of lentil in order to address the effect of climate change, to adapt in new cropping systems niches such as mixed cropping, relay cropping, etc. and to meet consumers’ preference.     

河北省大豆推广品种遗传多样性分析

利用主要农艺性状以及SSR和AFLP2种分子标记,对河北省41个大豆推广品种进行遗传多样性分析,以便为种质资源利用和创新提供依据。农艺性状聚类结果将41个材料划分为3个类群和2个特殊品种,聚类结果与材料系谱来源相差悬殊,不能反映材料间亲缘关系。SSR和AFLP数据聚类结果将41个材料划分为4个SAG（SSR and AFLP—basedgroups）分子类群。30对SSR引物共检测出135个等位变异,平均每个位点上有4．47个等位变异,SSR的遗传多样性指数（Simpson）分布范围为0．0928～0．7800,平均值为0、6442。10对AFLP引物共扩增出93个多态性标记,平均每对引物9．3个多态性标记。品种间的遗传相似系数（GS）变化范围为0．5877～0．9868,平均值变化范围为0．6732～0．7653,总体平均值为0.7237,遗传相似系数较高,说明材料间遗传变异较小。     

Evaluation of SSR Markers for the Assessment of Genetic Diversity and Fingerprinting of Gossypium hirsutum Accessions

A total 177 simple sequence repeat (SSR) markers were screened using a set of 47 Upland cotton genotypes comprising 14 commercial varieties, 14 germplasm accessions and 19 advanced breeding lines to identify informative markers for genetic diversity assessment and fingerprinting in G. hirsutum. Only 21% (381177) of SSR markers tested showed polymorphism with a mean of 2.18 alleles per locus and with average polymorphism information content (PIC) of 0.32. The SSR markers revealed a Jaccard’ similarity coefficient ranging between 0.43 and 0.89, with an average of 0.67 among accessions. Cluster analysis using unweighted pair group method with arithmetic averages (UPGMA) and principal component analysis (PCA) indicated that majority of the genotypes were very closely related. All the 47 genotypes showed heterorygosity for at least one of the SSR loci. We discovered 19 rare and 6 unique alleles among the tested genotypes of cotton. Fingerprint based on all the 38 loci revealed a probability of identical match by chance of 3.98x10. A set of ten SSR markers was identified which could distinguish all the 47 genotypes with a moderate probability of identical match by chance (X?_D ⁿ = 0.01).     

Genetic analysis of Indian aromatic and quality rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) germplasm using panels of fluorescently-labeled microsatellite markers

Genetic relationships among Indian aromatic and quality rice (Oryza sativa) germplasm were assessed using 30 fluorescently labeled rice microsatellite markers. The 69 rice genotypes used in this study included 52 Basmati and other scented/quality rice varieties from different parts of India and 17 indica and japonica varieties that served as controls. A total of 235 alleles were detected at the 30 simple sequence repeat (SSR) loci, 62 (26.4%) of which were present only in Basmati and other scented/quality rice germplasm accessions. The number of alleles per locus ranged from 3 to 22, with an average of 7.8, polymorphism information content (PIC) values ranged from 0.2 to 0.9, with an average of 0.6, and the size range between the smallest and the largest allele for a given microsatellite locus varied between 3 bp and 68 bp. Of the 30 SSR markers, 20 could distinguish traditional Basmati rice varieties, and a single panel of eight markers could be used to differentiate the premium traditional Basmati, cross-bred Basmati, and non-Basmati rice varieties having different commercial value in the marketplace. When estimates of inferred ancestry or similarity coefficients were used to cluster varieties, the high-quality Indian aromatic and quality rice genotypes could be distinguished from both indica and japonica cultivars, and crossbred varieties could be distinguished from traditional Basmati rices. The results indicate that Indian aromatic and quality germplasm is genetically distinct from other groups within O. sativa and is the product of a long, independent pattern of evolution. The data also suggest that there is scope for exploiting the genetic diversity of aromatic/quality rice germplasm available in India for national Basmati rice breeding programs.Electronic Supplementary Material Supplementary material is available for this article at .     

Evaluation of the genetic diversity and population structure of sesame (Sesamum indicum L.) using microsatellite markers

Sixteen polymorphic microsatellite (SSR) markers, developed from an SSR-enriched genomic DNA library of sesame (Sesamum indicum L.), were used to assess genetic diversity, phylogenetic relationships, and population structure among 150 sesame accessions collected from 22 countries. A total of 121 alleles were detected among the sesame accessions. The number of detected alleles varied from 2 to 18, with an average of 7.6 alleles per locus. Polymorphism information content values ranged from 0.03 to 0.79, with an average of 0.42. These values indicated an excess of heterozygous individuals at 16 loci and an excess of homozygous individuals at three loci. Of these, 32 genotype-specific alleles were identified at 11 of 16 polymorphic SSR markers. Cluster analyses were performed by accession and population, revealing a complex accession distribution pattern with mean genetic similarity coefficient of 0.45 by accession and 0.52 by population. The wide variation in genetic similarity among the accessions revealed by SSRs reflected a high level of polymorphism at the DNA level. Model-based structure analysis revealed the presence of three groups that were basically consistent with the clustering results based on genetic distance. These findings may be used to augment the sesame germplasm and to increase the effectiveness of sesame breeding.     

棉花耐盐相关种质资源遗传多样性分析

为了解我国棉花耐盐相关种质资源的遗传变异,利用88对SSR引物对23份棉花耐盐材料和24份盐敏感材料进行遗传多样性分析。88个SSR位点在47份材料中共检测出338个等位基因变异,平均每个位点有3.841个;其中耐盐材料中检测出333个,盐敏感材料中检测出312个。耐盐材料的位点多态信息含量(PIC)、每个位点的有效等位基因数(Ne)、基因型多样性(H′)分别为0.613、2.929和1.083,盐敏感材料的PIC、Ne、H′分别为0.605、2.883和1.071。耐盐材料和盐敏感材料的Jaccard相似性系数分别在0.530–0.979和0.525–0.878之间,遗传相似性系数总体平均值接近,但耐盐材料的变化幅度更大。用类平均法(UPGMA)聚类将47份材料分成3个类群。总体而言,大多数材料之间的遗传相似性系数较高,表明我国陆地棉耐盐相关种质资源遗传基础狭窄。本结果为棉花耐盐育种中亲本的选配和优势组合的预测以及耐盐资源的合理利用等提供了基础资料。     

Genetic diversity in basmati rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) germplasm as revealed by microsatellite (SSR) markers

Genetic diversity among rice genotypes, including 15 indica basmati advance lines and 5 basmati improved varieties were investigated by 28 SSR markers including one indel marker. The SSRs covered all the 12 chromosomes that distributed across the rice genomes. The mean number of alleles per locus was 3.60, showing average number of polymorphism information content was 0.48. A total of 101 alleles were also identified from the microsatellite marker loci. A number of SSR markers were also identified that could be utilized to differentiate between rice genotypes. Pair wise Nei’s genetic distance between rice genotypes ranged from 0.07 to 0.95. The dendrogram based on cluster analysis by using SSR polymorphism that grouped the 20 genotypes of rice in to five clusters based on their genetic similarity. The result could be useful for the identification and selection of the diverse genotypes for the future cross breeding program and development of new rice varieties.     

Molecular Identification and Genetic Diversity Analysis of Chinese Sugarcane (<Emphasis Type="Italic">Saccharum</Emphasis> spp. Hybrids) Varieties using SSR Markers

Sugarcane (Saccharum spp. hybrids) is an important sugar and renewable bio-energy crop with a high aneu-polyploidy and complex genome. The complex characteristics of sugarcane genome enhance the difficulty of selecting elite varieties in sugarcane breeding program. The objectives of this study were to establish the molecular identities (ID) of 91 nationally or provincially released Chinese sugarcane varieties and to evaluate the extent of genetic diversity among these varieties using SSR DNA markers and two fingerprinting systems, i.e., capillary electrophoresis (CE) and polyacrylamide gel electrophoresis (PAGE). A total of 151 SSR alleles together with 20 new alleles were detected by CE and 117 SSR alleles were detected by PAGE. Primer pairs SMC336BS, SMC31CUQ, and SMC597CS amplified more than eight alleles detectable by either CE or PAGE. Polymorphism information content (PIC) values of the SSR markers varied from 0.71-0.98 with an average of 0.90 for CE, or from 0.55-0.95 with an average of 0.84 for PAGE. UPGMA method classified the 91 varieties based on the CE data into four major groups with pair-wise similarity coefficients ranging from 58% to 95%. The genetic similarity estimates within and between the four groups varied from 0.31 to 0.87, with a mean of 0.49. Our results illustrated that the 21 SSR primer pairs in combination with CE or PAGE detection system could be a very useful working tool for molecular identification of sugarcane varieties, genetic diversity assessment, and parental selection in sugarcane breeding.     

香稻资源遗传多样性的比较

利用60个水稻SSR标记, 对来自国内外的370份香稻材料的遗传多样性进行了比较分析。结果共检测到361个等位基因, 每个位点的等位基因变幅为2~10个, 平均Nei基因多样性指数(He)为0.663, 变幅为0.104(RM308)~0.885(RM2634)。籼粳亚种间的遗传多样性具有明显差异, 籼稻的等位基因数和Nei基因多样性指数均高于粳稻。地方品种的遗传多样性高于选育品种, 选育品种等位基因数仅为地方品种的86.5%。分子方差分析表明, 香稻材料中总变异的43.08%是由于亚种间的遗传差异引起的。不同稻区的遗传分化程度总体介于1.69%~14.40%之间。其中, 华南与西南、华中与西南地方品种间遗传差异的分化程度达显著水平。聚类分析将参试材料明显分为籼粳两大类, 同时地域相同(稻区)、相邻省份的香稻材料基本归为同一类群。     

Genetic diversity,population structure and association analysis in linseed (<Emphasis Type="Italic">Linum usitatissimum</Emphasis> L.)

The present investigation aimed to explore the level of genetic diversity, determine the population structure in a larger set of germplasm of linseed using microsatellite marker and identify linked markers through association mapping. A total of 168 accessions of linseed were evaluated for major agro-economic traits and SSRs markers deployed for diversity assessment. A total of 337 alleles were amplified by 50 SSRs ranging from 2 to 13 with an average of 6.74 ± 2.8 alleles per loci. The neighbor joining based clustering grouped all the accessions into three major clusters that were also confirmed by scatter plot of PCoA. While model based clustering determined four sub-populations (K = 4). Further, analysis of molecular variance analysis considering three population showed that maximum variation (79%) was within the population. We identified one putative SSR marker (Lu_3043) linked with days to 50% flowering through both GLM and MLM analysis of association mapping. The results of this preliminary study revealed genetic diversity, population structure in linseed and linked marker which could be utilized in future breeding program.     

A genetic linkage map of microsatellite,gene-specific and morphological markers in diploid <Emphasis Type="Italic">Fragaria</Emphasis>

Knowledge of the genetic diversity of a species is important for the choice of crossing parents in line and hybrid breeding. Our objective was to investigate European winter triticale using simple sequence repeat (SSR) markers and the coancestry coefficient (f) with regard to genetic diversity and grouping of germplasm. Three to five primer pairs for each of the 42 chromosomes were selected to analyse 128 European winter triticale varieties and breeding lines. SSR analysis resulted in the identification of 657 alleles with an average of 6.8 alleles per primer pair. The average polymorphism information content (PIC) for polymorphic markers was 0.54. Correlation between f and genetic similarity (GS) estimates based on Rogers Distance was low (r_f×GS(ABDR)=0.33). The analysis of molecular variance (AMOVA) revealed that 84.7% of the total variation was found within breeding companies, and 15.3% among them. In conclusion, SSR markers from wheat and rye provide a powerful tool for assessing genetic diversity in triticale. Even though no distinct groups within the European winter triticale pool could be detected by principal co-ordinate analysis, this study provides basic information about the genetic relationships for breeding purposes.Electronic Supplementary Material Supplementary material is available in the online version of this article at Communicated by H.C. Becker     

Allelic reduction and genetic shift in the Canadian hard red spring wheat germplasm released from 1845 to 2004

Analysis of genetic diversity changes in existing gene pools of cultivated crops is important for understanding the impact of plant breeding on crop genetic diversity and developing effective indicators for genetic diversity of cultivated plants. The objective of this study was to assess genetic diversity changes in 75 Canadian hard red wheat (Triticum aestivum L.) cultivars released from 1845 to 2004 using 31 simple sequence repeats (SSRs) markers. A total of 267 SSR alleles were detected, and their allelic frequencies ranged from 0.01 to 0.97, with an average of 0.14. Significant allelic reduction was observed at only four SSR loci for the cultivars released from 1970 onwards. However, 51 alleles (about 19%) present in pre-1910 cultivars were undetected in cultivars released after 1990 and were spread over 27 SSR loci. The proportion of SSR variation accounted for by six breeding periods was 12.5%, by four ancestral families, 16.5%, and by eight breeding programs, 8.4%. The average genetic diversity measured by three different band-sharing methods did not change significantly among cultivars released from different breeding periods, breeding programs, and ancestral families. However, genetic shift was obvious in the cultivars released over the six breeding periods, reflecting well the various breeding efforts over years. These results clearly show the allelic reduction and genetic shift in the Canadian hard red spring wheat germplasm released over time. Consequently, more effort needs to be made to broaden the wheat breeding base and conserve wheat germplasm.     

Patterns of subspecies genetic diversity among oilseed <Emphasis Type="Italic">Brassica rapa</Emphasis> as revealed by agro-morphological traits and SSR markers

Brassica rapa (2n = 20, AA genome) is an important oil yielding species of the family Brassicaceae and characterized by wide range of genetic and morphological subtypes suitable for cultivation under diverse agro-climatic regions of India. In this study, genetic diversity among three subspecies of B. rapa including yellow sarson, toria and outlier brown sarson was estimated using various agro-morphological traits and simple sequence repeat (SSR) markers. Maximum variability was recorded for siliqua angle (Coefficient of variation = 30.9%), followed by seeds/siliqua (CV = 18.8%), leaf length (CV = 10%) and plant height (CV = 16.8%). Principal component analysis explained more than 50% of the total observed morphological variability for first two components. Of the 107 SSR markers tested, 80 generated reproducible, clear and distinct amplicons of which, 65 (81.25%) were found polymorphic. The number of alleles at each locus ranged from 2 to 7, with an average of 3.03 alleles per marker. A total of 197 alleles were detected at 65 SSR loci with average PIC value of 0.457 and a mean resolving power of 3.04. Neighbor-Joining cluster analysis based on morphological traits and SSR markers separately classified all the 28 genotypes into five major groups. The population structure analysis resulted into three sub-populations with certain extent of admixture among the earlier established taxonomic sub-groups. Twenty-three unique alleles were detected in thirteen B. rapa varieties. The clustering analysis and principal coordinate analysis outlined the genetic relationships among different varieties belonging to the three subspecies of B. rapa. Genetically diverse genotypes as illustrated by score plots and from the clustering patterns brought out the wide range of diversity present among B. rapa genotypes and the underlying options available for selecting parental genotypes for hybridization and developing high yielding cultivars suitable for Indian conditions.     

宁夏60份粳稻种质资源遗传多样性分析

试验用SSR分子标记对60份宁夏粳稻种质资源进行遗传多样性分析。103对SSR引物表现多态性的有58对,共扩增出212条多态性条带,等位变异范围为2～9,平均每对引物3.7个;多态性信息含量(PIC)变幅为0.032～0.788,平均为0.403;高多态性位点主要发生在3号、6号和11号染色体上,而无多态性或低多态性位点主要发生在1号和10号染色体上;成对供试材料的遗传相似系数GS值变幅为0.642～0.958,平均为0.790,单个供试材料的平均GS值变幅为0.710～0.816,平均为0.781,亲缘关系较近;UPGMA聚类表明,在遗传相似系数约0.785处,供试材料可被分为11类,大部分材料被聚在一类中。