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1.
As introns are vulnerable to changes such as insertions and deletions when exposed to various evolutionary forces, they constitute a repository for developing genetic markers based on intron length polymorphisms (ILP). This study developed a set of genetic markers that use the potential intron length polymorphism in resistance gene analogs (RGAs) in Zea mays. By searching the genome of Zea mays B73 for the homologs of 73 R genes which have already been identified in plants, we found 861 RGAs, 632 of which have at least one intron that can serve as putative markers targeting the intron length polymorphism in RGAs (RGA-ILP). We developed 1972 candidate markers via electronic PCR (e-PCR) with primer pairs designed in each pair of exonic regions that flank an intron. Furthermore, the performance of RGA-ILP among four maize inbred lines (Huangzao4, B73, Mo17, and Dan340) was evaluated with 69 pairs of randomly selected primers. Of them, 46.4% showed bands that had discriminating length polymorphism, and between any two of the inbred lines the proportion of polymorphism ranged from 23.2 to 31.9%. To make it convenient to use these markers for those interested in molecular breeding of disease-resistant maize, we provide all related information in a web-based database named MaizeRGA, which is available at .  相似文献   

2.
DNA polymorphism of randomly selected genes in rice cultivars was analyzed by the polymerase chain reaction-restriction fragment-single strand conformation polymorphism (PCR-RF-SSCP) technique. Single DNA fragments were amplified from genomic DNA of the Nipponbare cultivar by 671 primer pairs among the 1000 primer pairs tested. PCR-RF-SSCP analysis using the 671 primer pairs detected polymorphism in 108 DNA fragments between 17 japonica paddy-rice cultivars. An average of 36.9 DNA fragments showed polymorphism between any pair of japonica paddy-rice cultivars. The nucleotide sequences of the polymorphic DNA fragments were determined for 50 alleles of 45 genes together with Nipponbare alleles. In these genes, 142 SNPs and 32 insertions/deletions were identified. Among these 174 sequence variations, 71 were in exons, 78 in introns, and 25 in unassigned regions. There were 28 alleles which had sequence variations in the exons. One allele had a 1-bp deletion in the exon causing a frame-shift mutation, 15 alleles had missense mutations, and the other 12 alleles had synonymous changes and/or sequence variations in 3' untranslated regions. The number of genes having sequence variations between the rice cultivars and the functional implications of the identified SNPs are herein discussed.  相似文献   

3.
32个柿主栽品种SSR图谱构建及遗传变异分析   总被引:5,自引:0,他引:5  
以32份柿主栽品种为试验材料,利用SSR标记技术构建其指纹图谱并进行遗传多样性分析。从78对候选引物中筛选出20对多态性高、稳定性好的引物作为核心引物,构建柿主栽品种SSR指纹图谱。结果显示:(1)20对引物在32份材料中共扩增出183条多态性条带,每对引物扩增出3~20条不等,平均每对引物扩增出9.15条,多态性比率为81.3%。各个位点的杂合度在0.410 3~0.914 3之间,平均为0.702 7。(2)8对引物在12个品种上具有特征带型,采用5对引物进行组合鉴定即可将32个柿品种完全区分开。(3)依据SSR带型特征,对每对引物生成的不同带型直接编号,简化柿SSR带型记录方法,并利用每个品种的带型编号,建立其DNA指纹图谱,结果表明,核心引物组合法比特征谱带法更适用于构建中国柿主栽品种DNA指纹图谱。(4)根据系统聚类分析将32个柿主栽品种分为两大类,品种间的亲缘关系与地理来源具有一定的相关性。  相似文献   

4.
目的:用于芜菁的简单序列重复(SSR)标记数量有限,初步探索多态性较好SSR的结构特性,开发更多的SSR引物,有助于芜菁的研究。方法:开发680对新的SSR引物,以2个芜菁品种为模板进行多态性扩增,筛选出多态性较好的引物。结果:565(83.1%)对引物在2种芜菁之间能够有效扩增,有多态性的引物有141对(20.7%);SSR的长度与其多态性水平之间没有直接的线性关系,但SSR基序碱基数与重复次数和多态性水平之间存在一定的联系,即3碱基为基序、7次重复的SSR多态性较好。结论:SSR的类型与引物的多态性之间有一定的联系。  相似文献   

5.
To map the QTLsof Fusarium moniliforme ear rot resistance inZea mays L., a total of 230 F2 individuals, derived from a single cross between inbred maize lines R15 (resistant) and Ye478 (susceptible), were genotyped for genetic map construction using simple sequence repeat (SSR) markers and amplified fragment length polymorphism (AFLP) markers. We used 778 pairs of SSR primers and 63 combinations of AFLP primers to detect the polymorphisms between parents, R15 and Ye478. From the polymorphic 30 AFLP primer combinations and 159 SSR primers, we scored 260 loci in the F2 population, among which 8 SSR and 13 AFLP loci could not be assigned to any of the linkage groups. An integrated molecular genetic linkage map was constructed by the remaining 151 SSR and 88 AFLP markers, which distributed throughout the 10 linkage groups of maize and spanned the genome of about 3463.5 cM with an average of 14.5 cM between two markers. On 4 chromosomes, we detected 5 putative segregation distortion regions (SDRs), including 2 new ones (SDR2 and SDR7). The other 3 SDRs were located near the regions where gametophyte genes were mapped, indicating that segregation distortion could be partially caused by gametophytic factors.  相似文献   

6.
Stearoyl-acyl carrier protein desaturase (SAD, EC 1.14.99.6) produces oleic acid (18:1 9) by desaturating 18:0. SAD genes have been targets for breeding and engineering oilseed crops with increased stearic acid (18:0). Our aim was to clone, describe, and develop genetic markers for the SAD genes of sunflower (Helianthus annuus L.). Nineteen SAD cDNA clones were partially sequenced and found to belong to two groups. Full-length cDNAs from each group (SAD6 and SAD17) were completely sequenced. The amino acid identity of SAD6 and SAD17 was 89%. Both genes were strongly expressed in developing seeds, moderately expressed in leaves and flowers, and weakly expressed in cotyledons, roots, and stems. One intron was found in SAD6 and two introns were found in SAD17. The SAD introns from two inbred lines (HA370 and HA372) were sequenced and found to vary in length and nucleotide sequence. The length variants were caused by monomeric repeat length differences, insertions, and deletions. Three long poly-T repeats (T9 to T39) were found in one of the SAD17 introns. Three short adjacent CA repeats were found in the 5-untranslated region of SAD6. DNA fragment length polymorphism (DFLP), single-strand conformational polymorphism (SSCP), and simple sequence repeat (SSR) markers were developed for SAD6 and SAD17 by developing primers to flank introns or the CA repeats. Two of six DFLP, four of six SSCP, and one of two SSR markers were polymorphic among eight elite inbred lines. The polymorphic information contents for DFLP, SSCP, and SSR markers were 0.18, 0.37, and 0.30, respectively. Most of the polymorphisms were caused by intron fragment length polymorphisms. Introns may be an excellent source of hypervariable markers in sunflower and other crop plants.  相似文献   

7.
To detect DNA polymorphisms in the peanut, we screened 26 polymorphic primers using intron–exon splice junction (ISJ), universal rice primer (URP), and directed amplification of minisatellite region DNA (DAMD) techniques. Amplification of genomic DNA of 16 peanut accessions yielded 121 ISJ, 50 URP, and 25 DAMD fragments, of which 34, 25 and 16 were polymorphic, respectively. The range of polymorphism was 10.0–62.5%, averaging 27.7%, for ISJ; 20–80%, averaging 49.5%, for URP; and 28.6–50.0%, averaging 36.3%, for DAMD. In comparisons of multiplex ratio, average polymorphism information content, and marker index, the URP markers were relatively more efficient than ISJ and DAMD markers. Clustering results remained more or less the same with ISJ and URP markers. To the best of our knowledge, this is the first report on the study of the genetic diversity of the peanut using ISJ, URP, and DAMD markers.  相似文献   

8.
In bread wheat, 21 anchored simple sequence repeat (SSR) primer pairs detecting SSR length polymorphism and 42 anchored SSR primers detecting microsatellite‐anchored fragment length polymorphisms (MFLPs) are reported. Eight bread wheat genotypes were used for detecting polymorphism. The number of alleles in SSR analysis ranged from two to six, with a mean of 2.9 alleles per SSR. The number of polymorphic bands in MFLP ranged from two to 40, with a mean of 12.74 polymorphic bands/primer combination, the SSRs with CT/GA motifs giving the highest level of polymorphism (a mean of 18.37 bands). The average value of polymorphic information content (PIC) was 0.473 for SSRs and 0.061 for MFLP.  相似文献   

9.
Cowpea [Vigna unguiculata L. (Walp)] is grown mainly for its protein-rich grains and is consumed in various forms in sub-Saharan Africa. Average grain yield in farmers’ fields is generally low due to a number of biotic and abiotic stresses. One hundred and six cowpea accessions from Ghana, which had previously been evaluated for seedling drought tolerance, were used for this study. This paper attempts to use three multi-locus PCR-based molecular markers; simple sequence repeats (SSR), inter-retrotransposon amplified polymorphism (IRAP) and retrotransposon-microsatellite amplified polymorphisms (REMAP), to analyse genetic diversity in the cowpea accessions. Analysis of the polymorphic bands data indicated that 101 alleles were amplified among 121 cowpea genotypes (83.4%) from 16 SSR primer pairs out of a total of 30 SSR primer pairs. Likewisely, a total of 66 (54.5%) polymorphic bands were obtained from IRAP and a total of 114 (94.2%) highly polymorphic bands obtained from REMAP analysis. The outcome indicated the highly polymorphic nature of the DNA markers, as small groups of these molecular markers were found to be able to identify each of the accessions used. Microsatellite markers (SSRs) and retrotransposon-based markers, like IRAP and REMAP, were found to be highly polymorphic and informative, suggesting that genomic fingerprinting has a major role in characterizing populations.  相似文献   

10.
Analysis of a sugarcane (Saccharum spp.) EST (expressed sequence tag) library of 8678 sequences revealed approximately 250 microsatellite or simple sequence repeats (SSRs) sequences. A diversity of dinucleotide and trinucleotide SSR repeat motifs were present although most were of the (CGG)n trinucleotide motif. Primer sets were designed for 35 sequences and tested on five sugarcane genotypes. Twenty-one primer pairs produced a PCR product and 17 pairs were polymorphic. Primer pairs that produced polymorphisms were mainly located in the coding sequence with only a single pair located within the 5′ untranslated region. No primer pairs producing a polymorphic product were found in the 3′ untranslated region. The level of polymorphism (PIC value) in cultivars detected by these SSRs was low in sugarcane (0.23). However, a subset of these markers showed a significantly higher level of polymorphism when applied to progenitor and related genera (Erianthus sp. and Sorghum sp.). By contrast, SSRs isolated from sugarcane genomic libraries amplify more readily, show high levels of polymorphism within sugarcane with a higher PIC value (0.72) but do not transfer to related species or genera well.  相似文献   

11.
The use of maize microsatellite markers as a potential cost-effective method for molecular analysis of sugarcane was evaluated. Of the 34 primer pairs obtained from maize genomic libraries, 14 showed repeatable amplifications in Saccharum species clones, commercial hybrids, and the related genera Erianthus, accounting for 41.17% cross transferability. Complex banding patterns were encountered in sugarcane with the number of amplified fragments ranging from 7 to 14 with an average of 10 per primer, indicating the high polyploidy and heterozygosity existing in sugarcane. Phenetic analysis of the SSR polymorphisms produced by nine primers could clearly differentiate the different species of Saccharum and Erianthus and revealed the relationships that existed between them. Genetic similarity co-efficient indicated low diversity existing among the S. officinarum clones (82%) and a relatively higher level of diversity in the S. spontaneum clones (69.7%). Higher level of divergence of Erianthus from Saccharum was also clearly estabilished. Five primers produced genus- and species-specific fragments for Erianthus, S. spontaneum, S. officinarum, and S. barberi. The polymorphic primers, when tested on a panel of 30 commercial sugarcane cultivars, revealed a broad range (32.4-83.3%) of pair-wise similarity values, indicating their ability to detect high levels of polymorphism. A combination of two primers could differentiate all the varieties, further emphasizing their potential in fingerprinting and varietal identification.  相似文献   

12.
Ascochyta blight (AB), caused by Ascochyta rabiei (Pass.) Labr. (anamorph), is the most damaging disease of chickpea (Cicer arietinum L.) and is a serious biotic stress constraint for chickpea production. To understand the molecular diversity in A. rabiei populations of India, a total of 64 isolates collected from AB-infected chickpea plants from different agroclimatic regions in the North Western Plain Zone (NWPZ) of India were analyzed with 11 AFLP (amplified fragment length polymorphism) and 20 SSR (simple sequence repeat) markers. A total of 9 polymorphic AFLP primer pairs provided a total of 317 fragments, of which 130 were polymorphic and showed an average PIC value 0.28. Of the SSR markers, 12 showed polymorphism and provided a total of 29 alleles with an average PIC value 0.35. To the best of our knowledge, this is the first report on a comparison of AFLP and SSR diversity estimates in A. rabiei populations. The dendrogram developed based on AFLP and SSR data separately, as well as on the combined marker dataset, grouped the majority of AB isolates as per geographic regions. Model based population structure analysis revealed four distinct populations with varying levels of ancestral admixtures among 64 isolates studied. Interestingly, several AFLP primer combinations and SSR markers showed the locus/allele specific to AB isolates of certain regions, e.g., Hisar, Sriganganagar, Gurdaspur, and Sundarnagar. Genetic variability present in AB isolates of the NWPZ of India suggests the continuous monitoring of changes in A. rabiei population to anticipate the breakdown of AB resistance in chickpea cultivars grown in India.  相似文献   

13.
Ricinus communis is a versatile industrial oil crop that is cultivated worldwide. Genetic improvement and marker-assisted breeding of castor bean have been slowed owing to the lack of abundant and efficient molecular markers. As co-dominant markers, simple sequence repeats (SSRs) are useful for genetic evaluation and molecular breeding. The recently released whole-genome sequence of castor bean provides useful genomic resources for developing markers on a genome-wide scale. In the present study, the distribution and frequency of microsatellites in the castor bean genome were characterised and numerous SSR markers were developed using genomic data mining. In total, 18,647 SSR loci at a density of one SSR per 18.89 Kb in the castor bean genome sequence (representing approximately 352.27 Mb) were identified. Dinucleotide repeats were the most frequently observed microsatellites, although the AAT repeat motif was also prevalent. Using six cultivars as screening samples, 670 polymorphic SSR markers from 1,435 primer pairs (46.7 %) were developed. Trinucleotide motif loci contained a higher proportion of polymorphisms (48.5 %) than dinucleotide motif loci (39.2 %). The polymorphism level in the SSR loci was positively correlated with the increasing number of repeat units in the microsatellites. The phylogenetic relationship among 32 varieties was evaluated using the developed SSR markers. Cultivars developed at the same institute clustered together, suggesting that these cultivars have a narrow genetic background. The large number of SSR markers developed in this study will be useful for genetic mapping and for breeding improved castor-oil plants. These markers will also facilitate genetic and genomic studies of Euphorbiaceae.  相似文献   

14.
Simple sequence repeats (SSRs) have been widely used in maize genetics and breeding, because they are co-dominant, easy to score, and highly abundant. In this study, we used whole-genome sequences from 16 maize inbreds and 1 wild relative to determine SSR abundance and to develop a set of high-density polymorphic SSR markers. A total of 264 658 SSRs were identified across the 17 genomes, with an average of 135 693 SSRs per genome. Marker density was one SSR every of 15.48 kb. (C/G)n, (AT)n, (CAG/CTG)n, and (AAAT/ATTT)n were the most frequent motifs for mono, di-, tri-, and tetra-nucleotide SSRs, respectively. SSRs were most abundant in intergenic region and least frequent in untranslated regions, as revealed by comparing SSR distributions of three representative resequenced genomes. Comparing SSR sequences and e-polymerase chain reaction analysis among the 17 tested genomes created a new database, including 111 887 SSRs, that could be develop as polymorphic markers in silico. Among these markers, 58.00, 26.09, 7.20, 3.00, 3.93, and 1.78% of them had mono, di-, tri-, tetra-, penta-, and hexa-nucleotide motifs, respectively. Polymorphic information content for 35 573 polymorphic SSRs out of 111 887 loci varied from 0.05 to 0.83, with an average of 0.31 in the 17 tested genomes. Experimental validation of polymorphic SSR markers showed that over 70% of the primer pairs could generate the target bands with length polymorphism, and these markers would be very powerful when they are used for genetic populations derived from various types of maize germplasms that were sampled for this study.  相似文献   

15.
In this study, genetic diversity among 177 oat (Avena sativa L.) accessions including both white and red oat landraces and 36 commercial cultivars was studied for simple sequence repeat (SSR) loci. Thirty-one genomic and expressed sequence tags (EST)-derived primer pairs were selected according to high polymorphism from an initial 66 SSR batch. Markers revealed a high level of polymorphism, detecting a total of 454 alleles. The average gene diversity for the whole sample was 0.29. Genetic similarity, calculated using the Dice coefficient, was used for cluster analysis, and principal component analysis was also applied. In addition, population structure using a Bayesian clustering approach identified discrete subpopulation based on allele frequency and showed similar clustering of oat genotypes in four groups. Accessions could be classified into four main clusters that clearly separated the commercial cultivars, the red oat landraces and two clusters of white oat landraces. Cultivars showed less diversity than the landraces indicating a reduction of genetic diversity during breeding, whereas white oat landraces showed higher diversity than red ones. The average polymorphic information content of 0.80 for the SSR loci indicated the usefulness of many of the SSR for genotype identification. In particular, two markers, MAMA5 and AM04, with a total of 50 alleles and a high discrimination power (>0.90), were sufficient to discriminate among all commercial cultivars studied highlighting their potential use for variety identification.  相似文献   

16.
Chrysanthemum plants are popular worldwide as cut flowers, potted, and in gardens. Several hundred cultivars have been commercialized, indicating that there is substantial genetic variations that can be manipulated under cultivations to produce a wide array of phenotypic variation. To study the genetic diversity of chrysanthemum cultivars in Korea, we first identified simple sequence repeats from chrysanthemum expressed sequence tags generated by FLX 454 sequencing. A total of 1109 ESTs out of 18,226 chrysanthemum ESTs were identified to carry SSRs. A total of 16 out of 46 primer pairs exhibited several polymorphisms among 50 chrysanthemum cultivars. The number of alleles per locus varied from 1 to 15, with an average of 6.25 alleles. The expected heterozygosity ranged from 0 to 0.8958, whereas polymorphism information content ranged from 0 to 0.8872. Based on polymorphisms using 16 SSR markers, a phylogenetic tree was generated revealing four groups within the 50 cultivars showing various levels of genetic diversity. The 16 polymorphic chrysanthemum SSR markers generated in this study would be useful for studies of the genetic conservation, diversity, and population structure of commercial chrysanthemum cultivars as well as closely related species.  相似文献   

17.
对海岛棉产量和早熟性状进行QTL初步定位,为分子标记辅助育种提供依据。利用5200多对SSR引物筛选海岛棉品种新海3号和Giza82间的多态性引物,获得107对。以多态性引物检测新海3号×Giza82的190个F2:3家系,获得120个多态性位点。利用JoinMap3.0分析软件构建了一个包含22个连锁群,74个标记,标记间平均距离12.06 cM,全长893 cM,覆盖海岛棉基因组20.12%的分子标记遗传连锁图谱。采用复合区间作图法检测到21个与海岛棉产量性状和早熟性状有关的QTL,其中早熟性状检测到12个QTL,分别位于1、3、5、6、11、17、22共7个连锁群上;产量性状检测到9个QTL,分别位于1、4、5、6、7、16、22共7个连锁群上。研究结果为海岛棉产量性状和早熟性状的分子设计育种提供了有用的信息。  相似文献   

18.
Nachman MW  Crowell SL 《Genetics》2000,155(4):1855-1864
The Duchenne muscular dystrophy (Dmd) locus lies in a region of the X chromosome that experiences a high rate of recombination and is thus expected to be relatively unaffected by the effects of selection on nearby genes. To provide a picture of nucleotide variability at a high-recombination locus in humans, we sequenced 5. 4 kb from two introns of Dmd in a worldwide sample of 41 alleles from Africa, Asia, Europe, and the Americas. These same regions were also sequenced in one common chimpanzee and one orangutan. Dramatically different patterns of genetic variation were observed at these two introns, which are separated by >500 kb of DNA. Nucleotide diversity at intron 44 pi = 0.141% was more than four times higher than nucleotide diversity at intron 7 pi = 0.034% despite similar levels of divergence for these two regions. Intron 7 exhibited significant linkage disequilibrium extending over 10 kb and also showed a significant excess of rare polymorphisms. In contrast, intron 44 exhibited little linkage disequilibrium and no skew in the frequency distribution of segregating sites. Intron 7 was much more variable in Africa than in other continents, while intron 44 displayed similar levels of variability in different geographic regions. Comparison of intraspecific polymorphism to interspecific divergence using the HKA test revealed a significant reduction in variability at intron 7 relative to intron 44, and this effect was most pronounced in the non-African samples. These results are best explained by positive directional selection acting at or near intron 7 and demonstrate that even genes in regions of high recombination may be influenced by selection at linked sites.  相似文献   

19.
DNA polymorphism between two major japonica rice cultivars, Nipponbare and Koshihikari, was identified by AFLP. Eighty-four polymorphic AFLP markers were obtained by analysis with 360 combinations of primer pairs. Nucleotide sequences of 73 markers, 29 from Nipponbare and 44 from Koshihikari, were determined, and 46 AFLP markers could be assigned to rice chromosomes based on sequence homology to the rice genome sequence. Specific primers were designed for amplification of the regions covering the AFLP markers and the flanking sequences. Out of the 46 primer pairs, 44 amplified single DNA fragments, six of which showed different sizes between Nipponbare and Koshihikari, yielding codominant SCAR markers. Eight primer pairs amplified only Nipponbare sequences, providing dominant SCAR markers. DNA fragments amplified by 13 primer pairs showed polymorphism by CAPS, and polymorphism of those amplified by 13 other primer pairs were detected by PCR-RF-SSCP (PRS). Nucleotide sequences of the other four DNA fragments were determined in Koshihikari, but no difference was found between Koshihikari and Nipponbare. In total, 40 sequence-specific markers for the combination of Nipponbare and Koshihikari were produced. All the SNPs identified by AFLP were detectable by CAPS and PRS. The same method was applicable to a combination of Kokoromachi and Tohoku 168, and 23 polymorphic markers were identified using these two rice cultivars. The procedure of conversion of AFLP-markers to the sequence-specific markers used in this study enables efficient sequence-specific marker production for closely related cultivars.  相似文献   

20.
基于差减cDNA文库EST信息的月季花香突变体SSR标记的开发   总被引:2,自引:0,他引:2  
在前期月季花香突变体差减文库EST序列信息的工作基础上, 文章开发出新的与花香相关的SSR标记。从正反向差减文库391条EST中检索到10条含有10个SSR的序列, SSR的检出率为2.6%, EST-SSR的重复基元共搜索到10种。利用部分EST-SSRs序列设计了6对SSR引物, 以花香突变体‘往日情怀’及其野生型‘金银岛’DNA为模板, 对引物进行筛选, 5对引物有扩增条带, 其中3对引物有特异性扩增条带。同时利用这些可扩增的引物对典型芳香和无香两组月季栽培品种进行多态性检测, 发现这5对引物均显示多态性。表明所建立的SSR标记是一种可行而有效的方法。  相似文献   

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