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1.
Genetic diversity of 54 accessions of Aegilops tauschii from five countries was assessed using sequence-tagged microsatellites (or simple sequence repeats, SSRs) and amplified fragment length polymorphisms (AFLPs). In the case of AFLP analysis, a total of 256 amplification products obtained, 234 of them were polymorphic across all the 54 accessions. A total of 224 fragments were obtained from the 24 SSR primers and 219 of fragments were polymorphic across all the genotypes screened. Based on both AFLP and SSR markers, the highest percentage of polymorphisms were obtained in Iranian and accessions of unknown origin. The highest polymorphic information content (PIC) value was observed for SSRs (0.82) while the highest marker index (MI) value was for AFLPs (8.5) reflecting the hyper-variability of the first and the distinctive nature of the second system. Principal co-ordinate analysis (PCO) revealed congruent patterns of genetic relationships for both data sets, but did not group accessions strictly according to their geographical origins. Poor correlation was found between AFLP and SSR marker loci. This low association may be due to low number of AFLP and SSR markers. These results show that molecular markers can help to organize the genetic variability and expose useful diversity for breeding purposes.  相似文献   

2.
In the last few years, the renewed interest for emmer wheat (Triticum dicoccon Schrank) in Italy has stimulated breeding programs for this crop releasing improved genotypes obtained not only by selection from landraces, but even by crosses with durum wheat (Triticum durum Desf.) varieties. The purpose of this work has been to uncover the genetic make-up of some emmer × durum derivatives, specifically by comparing the differences from their parents. Genetic diversity of advanced breeding lines and varieties derived from a durum × emmer cross has been evaluated on the basis of AFLP and SSR markers in comparison with the corresponding emmer and durum wheat parent for addressing the seminal question of how much ‘wild’ variation remains after selection for agronomic type.  相似文献   

3.
The development of EST-SSR in foxtail millet (Setaria italica) for polymorphism and transferability study was reported here. From 1213 EST sequences, 30 SSRs were obtained and primers were designed for 26 SSRs. Among them, four pairs of SSR primers amplified polymorphic products in 12 foxtail millet cultivars and one accession of Setaria viridis, a wild relative of foxtail millet, with 10 alleles detected for the four loci and 2.5 alleles per locus. In addition, ten SSR markers could be transferred to other nine Gramineae species. The putative functions of 11 ESTs containing polymorphic and transferable SSRs were also identified.  相似文献   

4.
Worldwide genetic diversity in 200 individuals comprising 41 castor bean accessions was assessed using amplified fragment polymorphisms (AFLPs) and simple sequence repeats (SSRs). We found that, despite surveying five continents and 35 countries, genetic diversity in castor bean germplasm is relatively low (overall H e = 0.126 for AFLPs and 0.188 for SSRs) compared to estimates of genetic diversity in other plant species. Our data also show no geographic structuring of genotypes across continents or countries within continents. An assessment of the congruence between AFLP and SSRs indicates a low correlation (R 2 = 0.19) between the two data sets, but each marker class nonetheless shows similar patterns of low-genetic diversity and a lack of geographic structure. Our data do suggest that SSRs yield a higher percentage of polymorphic loci, higher heterozyosity and a greater range of genetic distances, and are therefore more informative than are AFLPs on a locus-by-locus basis. Based on comparisons with numerous other plant species, we suggest that the lower genetic variation in this worldwide collection may be due to one or more factors including: sampling strategies that have not captured the full extent of genetic variation in the species; artifactual variation due to long-term germplasm storage and seed regeneration; or intense selection followed by domestic cultivation of a limited number of castor bean genotypes, which are widely propagated for their horticultural and agro-economic value.  相似文献   

5.
Genetic diversity among some important Syrian wheat cultivars was estimated using Amplified Fragment Length Polymorphism (AFLP) markers. Five Triticum aestivum L. and 10 Triticum turgidum ssp. durum were analyzed with 11 EcoRI–MseI primer pair combinations. Of the approximately 525 detected AFLP markers, only 46.67% were polymorphic. Cluster analysis with the entire AFLP data divided all cultivars into two major groups reflecting their origins. The first one contained T. aestivum L. cultivars, and the T. turgidum ssp. durum cultivars and landraces were grouped in the second. Narrow genetic diversity among all cultivars was detected with an average genetic similarity of 0.884. The lowest similarity index (0.9) was found between Cham5 and Hamary (durum wheat), whereas this value was 0.93 between Salamony and Bouhouth 4 (T. aestivum L.). The narrow genetic diversity level indicates that these genotypes could be originated from the same source. AFLP analysis provides crucial information for studying genetic variation among wheat cultivars and provides important information for plant improvement.  相似文献   

6.
Genetic diversity among 40 accessions (Coffea canephora) of robusta coffee genepool available in India was determined in comparison with 14 representative samples from a C. canephora core collection and three accessions of C. congensis, using amplified fragment length polymorphism (AFLP) and simple sequence repeats (SSR) markers. Both these molecular approaches were able to generate unique fingerprints for each of the accessions analysed. All the 12 SSR primers used in the present study were found polymorphic, with an average of six alleles per primer pair. Comparative analysis revealed the higher amount of diversity in representatives from a core collection than in the Indian genepool. Moreover, a total of 205 polymorphic AFLP bands were scored in all the 57 accessions analysed. The genetic relationship among 57 accessions was compared on the basis of SSR and AFLP polymorphisms. Genetic similarity dendrograms showed high correlation between the two marker systems. This study clearly established the high amount of diversity present in core samples, which is not represented in Indian genepool. Furthermore, the three accessions of C. congensis did not exhibit any significant diversity from other robusta accessions supporting the school of thought that C. congensis forms a biotype of C. canephora. The potential use of SSRs and AFLP markers in genetic diversity analysis for better ex situ management and also for exploitation of diversity in breeding programmes is discussed.  相似文献   

7.
Genetic diversity was examined in a collection of 263 Indian bread wheat (Triticum aestivum L.) cultivars using 90 SSR markers. These cultivars were classified into Group I (pre-green revolution cultivars) and Group II cultivars (post-green revolution cultivars). SSR markers were also classified into Set-I SSRs (42 random genomic SSRs) and Set-II SSRs (48 SSRs associated with QTLs for grain weight). The SSRs belonging to Set-II exhibited relatively low level of polymorphism, suggesting that the SSRs associated with QTL for grain weight in wheat were probably under selection pressure during wheat breeding. AMOVA indicated that proportion of the variation within each of the two groups of cultivars accounted for most (87.59%) of the molecular variance, while the variation between the two groups of cultivars accounted for only 12.41% of the variance. The estimates of the average number of alleles/locus and gene diversity due to each of the two sets of SSRs suggested increase in overall genetic diversity after green revolution in Indian bread wheat cultivars. Differences were also observed in genetic diversity among cultivars from each of the six wheat growing agro-climatic zones of India. However, decade-wise analysis of genetic diversity among the post-green revolution cultivars indicated a progressive decline in genetic diversity, thus suggesting a need for involving diverse exotic, synthetic and winter wheat germplasm in Indian wheat breeding programs.  相似文献   

8.
The genetic relationships were assessed for the first time in Turkish durum wheat cultivars using AFLP markers. In the analysis, 18 AFLP primer combinations resulted in a total of 189 polymorphic loci. All of the selective primers used are Eco and Mse primers with three nucleotide extentions on the 3 ends. The number of polymorphic markers per primer combination ranged from 4 to 24. The relationships, among nine winter and six spring type durum wheat cultivars, obtained with various algorithms are in accordance with the known pedigree information of the cultivars. Based on `Nei72' genetic distance analysis, the most distant two cultivars are `Berkmen-469' (winter type) and `Diyarbakìr-88' (spring type), and the closest two are `Selçuklu-97' and `Sofu', with the values of 0.793 and 0.115, respectively. The closest two winter type cultivars are `Akbasak-073-44' and `Kunduru-414-44' (0.128).  相似文献   

9.
Chloroplast microsatellites (SSRs) are conserved within wheat species, yet are sufficiently polymorphic between and within species to be useful for evolutionary studies. This study describes the relationships among a very large set of accessions of Triticum urartu Thum. ex Gandil., T. dicoccoides (Körn. ex Asch. et Graebn.) Schweinf., T. dicoccon Schrank, T. durum Desf., T. spelta L., and T. aestivum L. s. str. based on their cpSSR genotypes. By characterising the chloroplast diversity in each wheat species in the evolutionary series, the impact on diversity of major evolutionary events such as domestication and polyploidyisation was assessed. We detected bottlenecks associated with domestication, polyploidisation and selection, yet these constrictions were partially offset by mutations in the chloroplast SSR loci that generated new alleles. The discrete cpSSR alleles and haplotypes observed in T. urartu and Aegilops tauschii, combined with other species specific polymorphisms, provide very strong evidence that concur with current opinion that neither species was the maternal and thus cytoplasmic donor for polyploid wheats. Synthetic hexaploid wheats possessed the same chloroplast haplotypes as their tetraploid progenitors demonstrating how the novel synthetic wheat lines have captured chloroplast diversity from the maternal parents, the chloroplast is maternally inherited and novel alleles are not created by genomic rearrangements triggered by the polyploidisation event.  相似文献   

10.
A total of 8117 suitable SSR-contaning ESTs were acquired by screening from a Malus EST database, among which dinudeotide SSRs were the most abundant repeat motif, within which, CT/TC followed by AG/GA were predominant. Based on the suitable sequences, we developed 147 SSR primer pairs, of which 94 pairs gave amplifications within the expected size range while 65 pairs were found to be polymorphic after a preliminary test. Eighteen primer pairs selected randomly were further used to assess genetic relationship among 20 Malus species or cultivars. As a result, these primers displayed high level of polymorphism with a mean of 6.94 alleles per locus and UPGMA cluster analysis grouped twenty Malus accessions into five groups at the similarity level of 0.6800 that were largely congruent to the traditional taxonomy. Subsequently, all of the 94 primer pairs were tested on four accessions of Pyrus to evaluate the transferability of the markers, and 40 of 72 functional SSRs produced polymorphic amplicons from which 8 SSR loci selected randomly were employed to analyze genetic diversity and relationship among a collection of Pyrus. The 8 primer pairs produced expected bands with the similar size in apples with an average of 7.375 alleles per locus. The observed heterozygosity of different loci ranged from 0.29 (MES96) to 0.83 (MES138), with a mean of 0.55 which is lower than 0.63 reported in genome-derived SSR marker analysis in Pyrus. The UPGMA dendrogram was similar to the previous results obtained by using RAPD and AFLP markers. Our results showed that these EST-SSR markers displayed reliable amplification and considerable polymorphism in both Malus and Pyrus, and will contribute to the knowledge of genetic study of Malus and genetically closed genera.  相似文献   

11.
Eighty-two genotypes of Rubus available in germplasm collections, nurseries and home gardens were collected and evaluated using a set of 16 simple sequence repeat (SSR) markers to estimate the level of genetic diversity and relatedness of the germplasm and for testing them on trueness-to-type. Each of the 16 SSRs was successful in amplifying alleles from most genotypes. Fifteen of the markers produced polymorphic bands, whereas marker RhM023 was monomorphic. The polymorphic information content among genotypes varied from 0.056 to 0.83 with an average of 0.348. A neighbor-joining analysis allocated the genotypes to four major clusters containing 11, 24, 39 and eight genotypes, respectively. Cluster I consists of floricane-fruiting cultivars originating from the Scottish and/or British breeding programs or cultivars which have those cultivars in their pedigree. Cluster II included cultivars that have ‘Autumn Bliss’ or ‘Tulameen’ in their pedigree. Cluster III consists of summer-bearing raspberry cultivars, some primocane-fruiting cultivars, and a few intermediate summer-fall-bearing types. Cluster IV consists of the blackberry ‘Navaho’ (R. fruticosus L.), the interspecific hybrid ‘Dorman Red’ and a few other raspberry varieties. A number of yellow fruited varieties was dispersed on three different clusters suggesting a convergent evolution of this trait. The pedigree of several genotypes could be confirmed using a Pedimap based approach, whereas other cultivars were found to be genetically identical. The results disclose the alarming narrow genetic base of Rubus resources in Germany. Broadening of this base is urgently needed.  相似文献   

12.
The aim of this study was to identify the group of highly polymorphic microsatellite markers for the identification of six pear cultivars (P. communis) and two individuals of wild pear (P. pyraster). From among 40 tested SSR markers, 19 were selected to profile genetic diversity in pear genotypes due to high polymorphisms. These markers showed high heterozygosity levels (0.5–1) and, on average, 6.4 alleles per marker were found. The set of microsatellite markers employed in this study demonstrated usefulness of microsatellite markers for the identification of pear genotypes. The examined wild forms were represented in this study by only two individuals of P. pyraster. It can be assumed that these forms were distinctly different from the cultivated pear cultivars.  相似文献   

13.
One hundred and thirty SSR markers from wheat, maize and sorghum were screened for the transferability to Paspalum. The transfer rate was 67.5, 49.0 and 66.8% respectively. This would be a very efficient approach for DNA marker development for species which are not well studied molecularly. The polymorphism level for transferred SSR markers was 51.5% within species (Paspalum vaginatum) and 87.1% among Paspalum species. The high level of polymorphism is directly related to the high degree of heterozygosity maintained by its way of reproduction, i.e. self-incompatibility. Forty transferred polymorphic SSR markers were selected and used for characterization and evaluation of seventy-three Paspalum accessions. In total, 209 polymorphic bands were detected from these 40 SSR markers, with an average of five polymorphic bands per marker. The Paspalum accessions clustered into three major groups. Two very similar dendrograms can be generated from either 109 or 209 polymorphic bands. This led us to determine that 18 of the transferred SSR markers were sufficient for genetically differentiating the investigated germplasm accessions. The number of SSR markers required for germplasm characterization and evaluation is discussed. This is the first report of the transfer of SSR markers from major field crops to newly emerged environmental turfgrasses.  相似文献   

14.
Twenty-five Pyrus communis L. cultivars including eight traditional Portuguese pears, and four commercial Pyrus pyrifolia (Burm.) Nak. (Japanese pear or `nashi') cultivars were analysed by RAPD and AFLP techniques focusing on their molecular discrimination and the assessment of their genetic relatedness. Twenty-five primers generated 324 RAPD markers, among which 271 (84%) were polymorphic. The AFLP technique, using seven primer combinations, revealed a similar level of molecular polymorphisms (87%), representing 418 polymorphic bands among a total of 478 scored in autoradiographs. The high reproducibility of RAPD and AFLP techniques was confirmed comparing DNA samples from different extractions and different digestions of DNA from the same plant. Three genetic similarity matrices and respective dendrograms were elaborated on using RAPD, AFLP or joint RAPD and AFLP data. Both molecular marker techniques proved their reliability to assess genetic relationships among pear cultivars. P. pyrifolia cultivars exhibit a closer genetic relatedness, clustering apart from P. communis cultivars. Within P. communis, `William's', as well as `Doyenne du Comice', cluster close to their hybrids. Most of the Portuguese cultivars tend to cluster together, indicating to constitute a relatively independent genetic pool, which can be of interest in pear breeding programs.  相似文献   

15.
A total of 561 amplified fragment length polymorphism (AFLP) loci were generated and used to study the genetic diversity of wild and cultivated genotypes of pigeonpea. Out of 561 marker loci, 558 were polymorphic with an average of 76.12 bands. Analysis of molecular variation (AMOVA) revealed significant strong population structure when genotypes were structured according to continent of origin (FST = 0.22) also when structured into cultivated and wild genotypes (FST = 0.16). Maximum polymorphic loci were observed in cultivated species C. cajan (352) which is due to more number of genotypes used while, a minimum number of 45 polymorphic bands were obtained in C. acutifolius. Highest (0.291) average gene diversity was recorded in species C. mollis and lowest (0.079) average gene diversity was recorded in C. acutifolius. The 33 genotypes grouped into 14 clusters at 26% Jaccard’s similarity coefficients. Clustering analysis revealed most cultivated genotypes grouped into one major cluster while, the wild genotypes grouped into many clusters at 26% Jaccard’s similarity revealing greater diversity within wild species as compared to cultivated genotypes. From among the various cultivated genotypes studied, four genotypes BRG 3, ICP 7035, TTB 7 and ICP 8863 were molecularly and morphologically diverse and were used as parental genotypes to study nature of inheritance and to identify markers linked to sterility mosaic disease.  相似文献   

16.
Amplified fragments length polymorphism (AFLP) was used to distinguish 20 cultivars of sesame (Sesamum indicum L.) and to elucidate the genetic relationship among these genotypes. The data were also used to estimate the usefulness of parameters currently used to assess the informativeness of molecular markers. A total of 339 markers were obtained using 8 primer combinations. Of the bands, 91% were polymorphic. Five primer combinations were able to distinguish all 20 cultivars used. None of the remaining three primer combinations could distinguish all accessions if used alone, but using all three combinations reduced the probability of a random match to 5 × 10−5. Polymorphic information content (PIC), resolving power (Rp) and marker index (MI) of each primer combination failed to correlate significantly with the number of genotypes resolved. Jaccard’s similarity coefficients ranged from 0.31 to 0.78. Fifteen cultivars were grouped by four UPGMA-clusters supported by bootstrapping values larger than 0.70. The grouping pattern was similar to the grouping generated by principal coordinate analysis. The results demonstrated that AFLP-based fingerprints can be used to identify unequivocally sesame genotypes, which is needed for cultivar identification and for the assessment of the genetic variability of breeding stocks. We recommend to use the number of cultivars identified by a primer combination instead of PIC, Rp and MI; and to calculate the maximal, instead of average probability of identical match by chance in the assessment of the informativeness of a marker for cultivar identification.  相似文献   

17.
Genetic variation present in wild and cultivated barley populations was investigated using two sources of microsatellite also known as simple sequence repeat (SSR) markers. EST-SSRs are derived from expressed sequences and genomic SSRs are isolated from genomic DNA. Genomic SSR markers detected a higher level of polymorphism than those derived from ESTs. Polymorphism information content was higher in genomic SSRs than EST-derived SSRs. This study showed that the EST-SSR markers developed in cultivated barley are polymorphic in wild and cultivated varieties and produced high quality markers. Ten of these functional markers were polymorphic across the accessions studied. EST markers indicated clearer separation between wild and cultivated barley than genomic SSRs. The EST-SSRs are a valuable source of new polymorphic markers and should be highly applicable to barley genetic resources, providing a direct estimate of functional biodiversity.  相似文献   

18.
Lolium and Festuca are two important genera of cool-season forage and turf grasses worldwide. Lolium temulentum L. (darnel ryegrass) has been proposed as a model species for genomics studies of cool-season forage and turf grasses. A study with 41 darnel ryegrass, three tall fescue (Festuca arundinacea Schreb.), two tetraploid fescue (F. glaucescens), and two meadow fescue (F. pratensis) genotypes was initiated to (i) identify a set of microsatellite (simple sequence repeats) markers useful for L. temulentum L., and (ii) to utilize such markers for assessing the genetic variability of L. temulentum accessions collected from different geographical regions of the world. A total of 40 tall fescue (TF) EST-SSRs and 60 Festuca–Lolium (F × L) genomic SSRs were screened on a subset of eight genotypes. The selected 30 tall fescue EST-SSRs and 32 F × L genomic SSRs were used for further analysis of genotypes. The TF-EST- and the F × L genomic-SSRs identified 10.3 and 9.3 alleles per marker, respectively with an average polymorphic information content (PIC) value of 0.66. The phenogram based on 319 EST-SSR and 296 genomic SSR fragments, grouped L. temulentum accessions into three major clusters except for accession ABY-BA 8892.78. Lolium temulentum accession ABY-BA 8892.78 did not cluster with any other accession. The Festuca clusters were distantly related with darnel ryegrass clusters with a similarity coefficient of 0.26. The selected set of tall fescue EST- and F × L genomic SSRs were useful in assessing L. temulentum genetic diversity and could benefit the genetic improvement of members of the Festuca–Lolium complex.  相似文献   

19.
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20.
The waxy character is achieved in durum wheat (Triticum turgidum L. var. durum) when the granule‐bound starch synthase activity is eliminated. The result is a crop that produces kernels with no amylose in the starch. The presence of two Waxy loci in tetraploid wheat permits the production of two partial waxy wheat genotypes. Advanced full and partial waxy durum wheat genotypes were used to study the effect of waxy null alleles on pasta quality. Semolina from full and partial waxy durum wheats was processed into spaghetti with a semicommercial‐scale extruder, and pasta quality was evaluated. Cooked waxy pasta was softer and exhibited more cooking loss than pasta made from traditional durum cultivars. These features were attributed to lower setback of waxy starch as measured with the Rapid Visco Analyser. High cooking loss may be due to the lack of amylose‐protein interaction, preventing the formation of a strong protein network and permitting exudates to escape. Waxy pasta cooked faster but was less resistant to overcooking than normal pasta. Partial waxy pasta properties were similar to results obtained from wild‐type pasta. This indicates that the presence of a single pair of functional waxy genes in durum wheat was sufficient to generate durum grain with normal properties for pasta production. Waxy durum wheat is not suitable for pasta production because of its softening effect. However, this property may offer an advantage in other applications.  相似文献   

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