Isolation and characterization of sequence‐tagged microsatellite sites markers in chickpea (Cicer arietinum L.)

In this study we report the isolation of microsatellite sequences and their conversion to sequence‐tagged microsatellite sites (STMS) markers in chickpea (Cicer arietinum L.). Thirteen putative recombinants isolated from a chickpea genomic library were sequenced, and used to design 10 STMS primer pairs. These were utilized to analyse the genetic polymorphism in 15 C. arietinum varieties and two wild varieties, C. echinospermum and C. reticulatum. All the primer pairs amplified polymorphic loci ranging from four to seven alleles per locus. The observed heterozygosity ranged from 0 to 0.6667. Most of the STMS markers also amplified corresponding loci in the wild relatives suggesting conservation of these markers in the genus. Hence, these polymorphic markers will be useful for the evaluation of genetic diversity and molecular mapping in chickpea.     

A first set of gene-derived polymorphic microsatellite markers in half-smooth tongue sole (<Emphasis Type="Italic">Cynoglossus semilaevis</Emphasis>)

Half-smooth tongue sole (Cynoglossus semilaevis) is a commercially important marine fish species in China. A set of type I microsatellite markers were identified through bioinformatic mining of the GenBank database. Thirteen of these markers showed polymorphisms through genotyping a sample of 30 individuals. A total of 47 alleles were detected, with an average of 3.6 alleles per locus. The number of alleles, observed and expected heterozygosity per locus ranged from two to five, from 0.14 to 0.93 and from 0.27 to 0.77, respectively. Three loci significantly deviated from Hardy-Weinberg equilibrium after Bonferroni correction (P < 0.0038) and no significant linkage disequilibrum between pairs of loci was found. The markers identified in this study will contribute to construction of genetic linkage maps and mapping of quantitative trait loci (QTL) of C. semilaevis.     

Isolation and characterization of microsatellite loci in wild and domestic turkeys (Meleagris gallopavo)

We describe the isolation, development and application of seven microsatellite loci in the eastern wild turkey, Meleagris gallopavo silvestris, as well as their amplification and levels of polymorphism in the domestic turkey. The number of alleles per locus ranged from 5 to 15 and average heterozygosity was high for almost all loci. Domestic turkeys showed significantly reduced numbers of alleles per locus and overall heterozygosities when compared to eastern wild turkeys. The high variability in these markers should provide the level of resolution required to continue studies of wild turkey population genetics.     

Development of microsatellite markers and analysis of intraspecific genetic variability in chickpea (Cicer arietinum L.)

Paucity of polymorphic molecular markers in chickpea (Cicer arietinum L.) has been a major limitation in the improvement of this important legume. Hence, in an attempt to develop sequence-tagged microsatellite sites (STMS) markers from chickpea, a microsatellite enriched library from the C. arietinum cv. Pusa362 nuclear genome was constructed for the identification of (CA/GT) _n and (CT/GA) _n microsatellite motifs. A total of 92 new microsatellites were identified, of which 74 functional STMS primer pairs were developed. These markers were validated using 9 chickpea and one C. reticulatum accession. Of the STMS markers developed, 25 polymorphic markers were used to analyze the intraspecific genetic diversity within 36 geographically diverse chickpea accessions. The 25 primer pairs amplified single loci producing a minimum of 2 and maximum of 11 alleles. A total of 159 alleles were detected with an average of 6.4 alleles per locus. The observed and expected heterozygosity values averaged 0.32 (0.08–0.91) and 0.74 (0.23–0.89) respectively. The UPGMA based dendrogram was able to distinguish all the accessions except two accessions from Afghanistan establishing that microsatellites could successfully detect intraspecific genetic diversity in chickpea. Further, cloning and sequencing of size variant alleles at two microsatellite loci revealed that the variable numbers of AG repeats in different alleles were the major source of polymorphism. Point mutations were found to occur both within and immediately upstream of the long tracts of perfect repeats, thereby bringing about a conversion of perfect motifs into imperfect or compound motifs. Such events possibly occurred in order to limit the expansion of microsatellites and also lead to the birth of new microsatellites. The microsatellite markers developed in this study will be useful for genetic diversity analysis, linkage map construction as well as for depicting intraspecific microsatellite evolution.     

Length polymorphism and allele structure of trinucleotide microsatellites in natural accessions of Arabidopsis thaliana

 The objective of this work was to assess the degree of trinucleotide microsatellite length polymorphism in the selfing species Arabidopsis thaliana. PCR amplifications of 12 microsatellite loci among 49 natural populations revealed between one to eight length variants (alleles) for each locus. The average number of alleles per locus was four and the average genetic diversity index was 0.43. Divergence between length variants was investigated at the nucleotide level. Several observations emerge from the sequence data: (1) for most loci, length polymorphism results only from variations in the number of trinucleotide repeats; (2) for a few others, some variability was noted in the flanking sequences; (3) for compound and interrupted loci containing two arrays of trinucleotide repeats, length variations preferentially affect the longest one. Five of the Arabidopsis thaliana accessions were clearly composed of two sublines. In 2 other accessions, some heterozygous individual plants, probably resulting from recent outcrosses, were found. A phylogenetic tree constructed on the basis of trinucleotide microsatellite allelic diversity shows that genetic relationships among the accessions are not correlated with their geographic origin. Received: 4 November 1997 / Accepted: 3 March 1998     

Microsatellites in Cassava (Manihot esculenta Crantz): discovery, inheritance and variability

 Fourteen microsatellites containing GA-repeats were isolated and characterized in cassava (Manihot esculenta Crantz, Euphorbiaceae). Microsatellite heterozygosity (h) was estimated in 48 accessions using (³²P)-end-labeled primers and in more than 500 accessions using fluorescence-based genotyping. Heterozygosity values ranged from 0.00 to 0.88 and the number of alleles detected varied from 1 to 15. The reproducibility of allele sizing was also assessed using fluorescence-based genotyping. The average inter-gel size difference was 1.03 nucleotides. Chi-square tests (χ²) were performed to analyse segregation distortion and the linkage between alleles segregating from either or both parents in an F₁ mapping population. Most microsatellite loci segregated in the expected 1 : 1, 1 : 2 : 1 or 1 : 1 : 1 : 1 ratio. Linkage was detected between loci segregating from either parent, and segregation distortion from the male parent was detected for locus GA-131. Approximately 80% of the microsatellites detected one or two alleles per accession, suggesting a low degree of microsatellite locus duplication, an unexpected finding for a putative allopolyploid, highly heterozygous species. The high h values of most microsatellites, their amplification in other Manihot taxa and their suitability for high-throughput, fluorescence-based genotyping, make microsatellites the marker of choice for germplasm characterization and saturation of the cassava map. Received: 4 September 1997 / Accepted 16 March 1998     

Development of 12 polymorphic microsatellite markers in <Emphasis Type="Italic">Coilia ectenes</Emphasis> Jordan and Seale, 1905 (Clupeiformes: Engraulidae) and cross-species amplification in <Emphasis Type="Italic">Coilia mystus</Emphasis> Linnaeus, 1758

In this study, twelve polymorphic microsatellite markers were developed for Coilia ectenes (synonym C. nasus). In a sample of 30 C. ectenes individuals in a Wuhan population from Yangtze River, a total of 78 alleles were detected, and the number of alleles per locus ranged from 3 to 12. The observed and expected heterozygosities ranged from 0.100 to 1.000 and from 0.098 to 0.899, respectively. Six loci significantly deviated from the Hardy-Weinberg equilibrium after Bonferroni correction (P < 0.004), and no significant linkage disequilibrium between pairs of loci was found. The applicability of these markers in a closely related species, C. mystus, was evaluated by cross-species amplification. These microsatellite markers will be useful in studies on population genetics, conservation genetics, and fishery management and in the construction of genetic linkage maps of C. ectenes and C. mystus.     

Sixteen novel microsatellite loci developed for the giant panda (Ailuropoda melanoleuca)

Sixteen novel microsatellite DNA loci were developed from the giant panda (Ailuropoda melanoleuca) using a magnetic-bead capture method. A total of 115 alleles were obtained for these markers, ranging from 4 to 12 alleles per locus (average 7.188). These loci exhibited high levels of polymorphic information content and expected heterozygosity, 0.558–0.855 (average 0.729) and 0.628–0.885 (average 0.778), respectively. Therefore, the allelic polymorphism and heterozygosity show that the giant pandas raised in China Research and Conservation Center possess abundant genetic variation. In addition, if the three markers showing null alleles were excluded, the remaining 13 microsatellite loci still presented extremely low non-exclusion probabilities of parentage (0.002), paternity (0.000) and identity (0.000). As a result, this new suit of microsatellite markers would be a very informative tool for the genetic and conservation studies of giant pandas.     

Identification of microsatellite markers from Cicer reticulatum: molecular variation and phylogenetic analysis

Microsatellite sequences were cloned and sequenced from Cicer reticulatum, the wild annual progenitor of chickpea (C. arietinum L.). Based on the flanking sequences of the microsatellite motifs, 11 sequence-tagged microsatellite site (STMS) markers were developed. These markers were used for phylogenetic analysis of 29 accessions representing all the nine annual Cicer species. The 11 primer pairs amplified distinct fragments in all the annual species demonstrating high levels of sequence conservation at these loci. Efficient marker transferability (97%) of the C. reticulatum STMS markers across other species of the genus was observed as compared to microsatellite markers from the cultivated species. Variability in the size and number of alleles was obtained with an average of 5.8 alleles per locus. Sequence analysis at three homologous microsatellite loci revealed that the microsatellite allele variation was mainly due to differences in the copy number of the tandem repeats. However, other factors such as (1) point mutations, (2) insertion/deletion events in the flanking region, (3) expansion of closely spaced microsatellites and (4) repeat conversion in the amplified microsatellite loci were also responsible for allelic variation. An unweighted pairgroup method with arithmetic averages (UPGMA)-based dendrogram was obtained, which clearly distinguished all the accessions (except two C. judaicum accessions) from one another and revealed intra- as well as inter-species variability in the genus. An annual Cicer phylogeny was depicted which established the higher similarity between C. arietinum and C. reticulatum. The placement of C. pinnatifidum in the second crossability group and its closeness to C. bijugum was supported. Two species, C. yamashitae and C. chorassanicum, were grouped distinctly and seemed to be genetically diverse from members of the first crossability group. Our data support the distinct placement of C. cuneatum as well as a revised classification regarding its placement.     

Isolation and characterization of polymorphic microsatellite loci from black sea bass (Centropristis striata) and cross-species amplification

Black sea bass (Centropristis striata) is an economically important serranid species. A number of 39 microsatellite loci were isolated from two enriched genomic library of C. striata. Eleven of these loci were polymorphic in a test population with alleles per locus ranging from 3 to 8, and observed and expected heterozygosities per locus from 0.26 to 1.00 and from 0.61 to 0.84, respectively. Four loci significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction and no significant linkage disequilibrium was found between pairs of loci. Cross-species amplification of these polymorphic microsatellite loci was performed in additional two related species. These polymorphic microsatellite loci would be useful for investigating genetic resource of C. striata and other related species.     

Isolation and characterization of polymorphic microsatellite loci in Castanopsis chinensis Hance (Fagaceae)

Twelve novel microsatellite loci were isolated and characterized from enriched genomic libraries of Castanopsis chinensis. Four previously reported microsatellites from Castanopsis cuspidata were cross-amplified in C. chinensis. Forty-two sample trees from a wild population were tested for polymorphism using a set of the 16 polymorphic microsatellites. The average allele number of these microsatellites was 4.6 per locus, ranging from 2 to 7. The ranges of observed and expected heterozygosity were 0.262–1.000 and 0.238–0.818, respectively. Significant deviations from Hardy–Weinberg equilibrium were detected at five loci and no linkage disequilibrium was observed.     

Polymorphic microsatellites in the Reeves's pheasant developed by cross-species amplification

Cross-species microsatellite amplification is an effective way of obtaining microsatellite loci for closely related taxa in bird species. The Reeves's pheasant, Syrmaticus reevesii, is a vulnerable species endemic to China. To improve population genetics and parentage analysis studies in this species, we obtained nine polymorphic microsatellite markers, in addition to the nine markers previously isolated, from the cross-species amplification of 52 markers. The number of alleles per locus varied between two and 12 with expected heterozygosity ranging from 0.298 to 0.714 (n = 107). The success rates of simulated paternity tests using CERVUS software improved at different confidence levels after adding these markers to the previous ones.     

Development and characterization of microsatellite markers for Psychotria tenuinervis (Rubiaceae), a shrub species from the Atlantic forest, and primers transferability from Coffea

The shrub species Psychotria tenuinervis (Rubiaceae) is native to the Brazilian Atlantic forest and is largely found within natural and disturbed forest fragments. Aiming to develop studies on population genetic structure of forest fragment species, eigth microsatellite markers were developed for P. tenuinervis. Also, 15 loci already developed for Coffea (Rubiaceae) were tested for transferability to this species. We utilized 45 individuals from natural populations of three different fragments-anthropic edge, interior fragment and natural edge, within the Brazilian Atlantic forest. The average number of alleles per locus was 2.5 (two–four alleles/locus). These loci will be useful for future population genetic studies aiming to the conservation and management of this species.     

Twelve novel polymorphic microsatellite loci developed from the Asiatic black bear (<Emphasis Type="Italic">Ursus thibetanus</Emphasis>)

Since the number and range of Asiatic black bear (Ursus thibetanus) are declining due to habitat loss and illegal trade, it is essential to take effective actions to reinforce the conservation of the remaining bear populations. In order to aid such conservation efforts, we developed 12 novel polymorphic microsatellite loci of Asiatic black bear from genomic DNA-enriched libraries in this paper. The number of alleles per locus in 24 individuals ranged from 3 to 10, the average observed heterozygosity per locus from 0.214 to 0.950, and the average expected heterozygosity per locus from 0.243 to 0.891. Eight loci followed Hardy–Weinberg expectations after Bonferroni correction for multiple comparisons. No significant linkage association was found among all these loci. The 12 polymorphic microsatellite loci will be helpful to the conservation of the Asiatic black bear.     

Isolation and characterization of microsatellites in the woody shrub,Calothamnus quadrifidus (Myrtaceae)

Microsatellite loci were developed for genetic analysis of the bird pollinated woody shrub Calothamnus quadrifidus. A genomic library was constructed and screened with dinucleotide and trinucleotide repeat sequences. Ten dinucleotide microsatellite markers were developed, and polymorphism in a population of C. quadrifidus was investigated for six of these markers, which showed an average of 12.7 alleles per locus. Mendelian inheritance of the loci was confirmed through analysis of open pollinated progeny arrays of 10 plants. These loci will be used to study gene flow patterns between isolated populations of this species in southwest Western Australia.     

Development of microsatellite DNA markers of silver carp (Hypophthalmichthys molitrix) and their cross‐species application in bighead carp (Aristichthys nobilis)

Forty‐four microsatellite DNA markers were developed for silver carp, and used to investigate polymorphisms of 41 wild silver carps and seven wild bighead carps collected from Jingzhou fragment of Yangtze River. In silver carp, 40 markers were polymorphic. A total of 297 alleles were detected at 40 polymorphic loci. The number of alleles per locus varied from two to 16 with an average of 7.4 and the expected heterozygosities of each locus ranged from 0.07 to 0.91 with an average of 0.69. All markers amplified both silver carp and bighead carp DNAs.     

Development of microsatellite marker loci for European hazelnut (<Emphasis Type="Italic">Corylus avellana</Emphasis> L.) from ISSR fragments

Polymorphic microsatellite markers were developed for European hazelnut (Corylus avellana L.) from the sequences of inter-simple sequence repeat (ISSR) fragments and flanking regions. Twenty-five ISSR primers were used to generate fragments for cloning. Of the 520 unique sequences obtained, 41 contained long internal repeats (≥20 bp) with flanking sequences sufficient for primer design. From these, we developed 23 new polymorphic microsatellite loci. The flanking sequences were obtained for fragment ends by chromosome walking, and an additional 47 polymorphic markers were developed. Two additional polymorphic markers were developed from a GA-enriched library. The 72 new marker loci were characterized using 50 diverse hazelnut accessions. For the internal repeat loci, the number of alleles per locus ranged from 2 to 16, with a mean of 7.52. Mean values for expected heterozygosity (H_e), observed heterozygosity (H_o), and polymorphism information content (PIC) were 0.62, 0.59, and 0.58, respectively. The estimated frequency of null alleles (r) was ≥0.05 at six of the 23 loci. For the 47 marker loci developed from fragment ends, the number of alleles per locus ranged from 2 to 16, with a mean of 7.30. Mean values for H_e, H_o, and PIC were 0.62, 0.47, and 0.58, respectively. The estimated frequency of null alleles (r) was ≥0.10 at 18 of the 47 loci. Of the 70 loci developed from ISSR and flanking sequences, 50 segregated in our mapping population and were assigned to linkage groups.     

Development and Linkage Analysis of 104 New Microsatellite Markers for Bay Scallop (Argopecten irradians)

For genetic analysis and linkage mapping of bay scallop (Argopecten irradians), a set of 120 novel simple sequence repeat markers were developed from microsatellite-enriched libraries and expressed sequence tags. An inter-subspecies hybrid bay scallop family (CC5) of 46 progeny was analyzed as the reference population to confirm polymorphism and test the segregation patterns of these loci. A total of 104 microsatellite markers were polymorphic in the reference family, among which 36 in female, 28 in male, and 40 in both parents, respectively. Linkage analysis allowed mapping these markers to 15 linkage groups, which is close to the haploid chromosome number of bay scallop (n = 16). Analysis of the 40 markers segregating in both parents showed a higher recombination rate in the female parent, with the average of female-to-male recombination ratio of 1.09:1 between linked pairs of markers. When null alleles were considered, there were 17 loci showing segregation distortion at the 5% significance level using the chi-square test. The microsatellite markers developed in this study provide a useful resource for future linkage mapping and quantitative loci analysis in A. irradians.     

Isolation and characterization of 18 polymorphic microsatellite loci from freshwater pearl mussel (<Emphasis Type="Italic">Cristaria plicata</Emphasis>)

Cristaria plicata was an important freshwater mussel for pearl culture in China. 18 polymorphic microsatellite markers were isolated and characterized using (CA)₁₅-enriched genomic library of C. plicata. These loci showed high levels of genetic polymorphism testing on 60 individuals sampled from Poyang Lake of Jiangxi Province, China. The number of alleles per locus ranged from 4 to 18. The expected (H _E) and observed heterozygosities (H _O) were 0.7232–0.8961 and 0.0000–1.0000, respectively. Four microsatellite loci were significantly deviated from Hardy–Weinberg equilibrium and no linkage disequilibrium was found. These microsatellite loci will be useful for assessment of genetic diversity and population structure in C. plicata.     

High variability and disomic segregation of microsatellites in the octoploid Fragaria virginiana Mill. (Rosaceae)

The objectives of the present study were to develop microsatellite markers for the wild strawberry, Fragaria virginiana, to evaluate segregation patterns of microsatellite alleles in this octoploid species, and assess genetic variability at microsatellite loci in a wild population. A genomic library was screened for microsatellite repeats and several PCR primers were designed and tested. We also tested the use of heterologous primers and found that F. virginiana primers amplified products in cultivated strawberry, Fragaria × ananassa Duch. and Fragaria chiloensis. Similarly, microsatellite loci developed from cultivated strawberry also successfully amplified F. virginiana loci. We investigated four microsatellite loci in detail, three developed from F. virginiana and one from cultivated strawberry. A survey of 100 individuals from a population of F. virginiana in Pennsylvania demonstrated high heterozygosities (H_e or gene diversity ranged from 0.80 to 0.88 per locus) and allelic diversity (12–17 alleles per locus), but individual plants had no more than two alleles per locus. Segregation patterns in parents and progeny of two controlled crosses at these four loci were consistent with disomic Mendelian inheritance. Together these findings suggest that the genome of F. virginiana is "highly diploidized" and at least a subset of microsatellite loci can be treated as codominant, diploid markers. Significant heterozygote deficiencies were found at three of the four loci for hermaphroditic individuals but for only one locus among females in this gynodioecious species.Communicated by J. Dvorak