PRIMER NOTE. Using the incomplete genome of the ectomycorrhizal fungus Amanita bisporigera to identify molecular polymorphisms in the related Amanita phalloides

We describe the cross‐genomic isolation of 13 single nucleotide polymorphisms (SNPs) and one variable microsatellite from five loci for the death cap mushroom Amanita phalloides. Microsatellite repeats were identified by searching the partial Amanita bisporigera genome. Flanking primers were designed for 25 of these microsatellite loci and tested for cross‐amplification in A. phalloides. One locus contained an interrupted, compound microsatellite, and four loci contained one to six SNPs. These results demonstrate the usefulness of even an incomplete genome to identify molecular markers for population studies in nonmodel organisms.     

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     

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     

Isolation and characterization of microsatellites loci in the lemon (Citrus limon)

This study reports the isolation and characterization of seven polymorphic microsatellite loci in Citrus. The loci were isolated from two libraries constructed from genomic DNA nonenriched for TC and AC repeats and enriched for AC repeats. These markers yielded four to nine alleles per locus (mean 6.14) in a survey of 32 Citrus cultivars. Average observed heterozygosity ranged from 0.43 to 0.72. The levels of polymorphism found in this study suggest that these microsatellite loci can become an important tool for genetic studies in Citrus.     

Polymorphic microsatellite repeats are not conserved between Leishmania donovani and Leishmania major

Thirteen sets of polymerase chain reaction (PCR) primers were designed to amplify microsatellite loci identified in the genome sequence of Leishmania major. Polymorphisms were detected in L. major at all loci. In Leishmania donovani only two of these loci were informative for classification purposes with this data set. The PCR products of all loci from one L. donovani strain were sequenced and it was found that the number of repeats in the microsatellite loci were either substantially reduced with respect to L. major or absent altogether. Consequently it is unlikely to be possible to use the genome sequence of L. major to identify polymorphic microsatellite loci in other Leishmania species.     

Development and characterization of microsatellite markers for parentage analyses of the coral reef damselfish (<Emphasis Type="Italic">Pomacentrus amboinensis</Emphasis>: Pomacentridae)

Five new polymorphic microsatellite loci were developed for the coral reef damselfish Pomacentrus amboinensis. Twenty-four individuals from two Great Barrier Reef populations were genotyped at the five loci, with numbers of alleles per locus ranging from 6–23 and observed heterozygosity between 0.42–0.92. In addition, the cross-species testing of six primers developed for Stegastes partitus revealed one primer (SpGATA40) that was also polymorphic for P. amboinensis. Due to high levels of polymorphism (≥14 alleles) in at least four of the six loci and a high proportion of tetranucleotide repeats, these microsatellite markers should be useful for parentage assignment as well as other investigations of individual relatedness.     

Isolation and characterization of novel polymorphic nuclear microsatellite markers from Ophrys fusca (Orchidaceae) and cross-species amplification

The present study reports the isolation and characterization of eight new polymorphic microsatellite loci from the sexually deceptive orchid Ophrys fusca. Microsatellites were isolated from two partially enriched genomic libraries using FIASCO (Fast Isolation by AFLP of Sequences COntaining repeats). Seventy-three loci were screened for primer design and primer pairs corresponding to eight different loci were selected for microsatellite characterization of two Portuguese populations. Total number of alleles per locus ranged from 10 to 32. All loci showed a high level of observed heterozygosity (H₀) ranging from 0.33 to 1 and were possible to amplify in 16 other species of Ophrys using the same primers. H. C. Cotrim and F. A. Monteiro have contributed equally to this work.     

Use of short microsatellites from database sequences to generate polymorphisms among Lycopersicon esculentum cultivars and accessions of other Lycopersicon species

A search of nearly 2000 sequences from Solanaceae species in the EMBL and Genbank databases yielded 220 microsatellites. Among these were 80 microsatellites from 675 Lycopersicon entries. Dinucleotide repeats, as well as (CAA)_n and (TAA)_n repeats, were over-represented in non-coding DNA. The other trinucleotide repeats were predominantly found in exonic DNA. PCR analysis of 44 of the microsatellite-containing Lycopersicon loci identified 36 primer pairs that yielded well-scorable fragments, or groups of fragments, in L. esculentum cultivars and accessions of Lycopersicon species. Twenty-nine of these amplified bands that were polymorphic among the four Lycopersicon species. Ten primer pairs generated polymorphic bands among seven tomato cultivars. Upon examining the number of microsatellites and the degree of polymorphisms in relation to the repeat type and motif, the type of DNA the microsatellite resided in, the length of the microsatellite, and the presence of imperfections in the microsatellite, only two significant correlations were found. (i) Imperfect repeats were less polymorphic among species than perfect repeats. (ii) The percentage of loci polymorphic among cultivars increased from 6% for the shortest loci (with eight or less repeat units) to 60% for the group with the longest repeats (12 repeat units or longer). Among the species, however, all length classes contained about 83% polymorphic loci. In general, 2–4 alleles were found for each locus among the samples of the test set. In a few cases, up to eight alleles were found. A combination of these microsatellite loci can therefore be useful in distinguishing cultivars of tomato, which are genetically very closely related to each other. Received: 9 August 1996 / Accepted: 23 August 1996     

Allelic variation,fragment length analyses and population genetic models: a case study on Drosophila microsatellites*

The allelic variation of 16 microsatellite loci from selected species of the Drosophila melanogaster and D. obscura group was determined. Intra‐ and interspecific sequence comparisons allowed discrimination of mutations affecting the repetitive microsatellite from those affecting the flanking regions. The hypotheses that slippage needs a minimum number of repeats in order to become efficient with respect to microsatellite variability, and of an increased mutation rate with increased length of the microsatellite are supported by the results of our analyses. There is in particular at the interrupted complex microsatellite locus BICOID in the species of the D. obscura group, extensive variation in the flanking regions in addition to length and sequence variation of the repetitive microsatellite. The allelic variation at this locus can hardly be explained by slippage alone. Estimates of microsatellite variability by fragment length analyses will pick up only a minor fraction of allelic variation at such loci, and conclusions that are based on the stepwise mutation model will not hold.     

Isolation and characterization of microsatellite loci in the flour mite Acarus siro

Thirteen microsatellites with dinucleotide repeats were isolated from genomic DNA in solution by hybridization capture. Eleven were evaluated against Acarus siro using a multiple‐tube approach to assess polymorphism and reliability of the results. The multiple‐tube method demonstrated the presence of null alleles due to low levels of DNA. Seven of the 11 microsatellite loci were polymorphic and six produced reliable amplification products, if results only from individuals that scored at all six loci were used in the analysis. These were evaluated in eight strains of A. siro. Two of the samples showed some genetic divergence using F_ST values.     

Development of new microsatellite primers for green and white sturgeon

Sixty-eight primer sets for microsatellite loci were developed from microsatellite motif enriched genomic libraries of pooled DNA from the polyploid green and white sturgeon (Acipenser medirostris and A. transmontanus). Four individuals from each species were screened for polymorphism at these loci. Forty-eight loci amplified in both species, and some exhibited species-specific amplification for white or green sturgeon (8 and 12 loci, respectively). The number of alleles per locus ranged from one to 12. At least 68% of the green and 65% of the white sturgeon loci we developed are polysomic.     

Microsatellite variation in a social insect

We undertook a study to explore the potential of microsatellite loci as genetic markers for investigating kinship patterns in a social waspParachartergus colobopterus. A plasmid library with small inserts was screened for several oligonucleotide repeat motifs. Positive clones were sequenced and several were selected for further work. PCR primers were constructed that would amplify the tandem repeat region and a number of female wasps were scored for variation in the number of tandem repeats at these loci. The five amplified loci were far more variable than allozymes, with an average heterozygosity of 0.35. This work was supported by NSF Grants BSR-9021514 and IBN-9210051.     

Twelve polymorphic microsatellite loci from a dinucleotide-enriched genomic library of Japanese Spanish mackerel (Scomberomorus niphonius)

In the study, 34 microsatellite loci were isolated from a dinucleotide-enriched genomic library of Japanese Spanish mackerel (Scomberomorus niphonius). And 12 microsatellite loci were found to be polymorphic between 3 and 8 alleles. The number of observed and expected heterozygosity per locus in 23 individuals ranged from 0.6087 to 1.0000 and 0.8908 to 0.9773, respectively. Two loci significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction analysis and there was no significant linkage disequilibrium found between pairs of loci. As a result, 12 microsatellite loci probably located on different chromosome pairs and these polymorphic microsatellite loci should provide sufficient level of genetic diversity to investigate the fine-scale population structure and evaluate the breeding strategy in S. niphonius. The authors Shi-Chao Xing and Gen-Bo Xu contributed equally.     

Characterization of polymorphic microsatellite loci within a young Boophilus microplus metapopulation

Nine microsatellite loci from the cattle tick Boophilus microplus were isolated and characterized within New Caledonia. This Pacific island was invaded by the cattle tick from a few immigration events dating from mid‐20th century. A population survey involving 94 adult ticks indicated monomorphism at one locus, presence of null alleles at another, and high genetic diversity (0.61–0.72) at seven loci apparently suitable for population genetics studies. This opens the opportunity to dissect the populational mechanisms involved in the spectacular capacity of B. microplus to cope with local environmental heterogeneity during its recurrent invasions of tropical areas.     

Identification of the most represented repeated motifs in Arabidopsis thaliana microsatellite loci

The major simple sequence repeats present in the Arabidopsis genome were identified by Southern hybridizations with 49 oligonucleotide probes matching all the possible combinations of motifs up to 4 nucleotides long. The method used allowed us to perform all the hybridizations under the same temperature conditions. A good correlation was observed with the data obtained from database analysis, indicating that the method can be useful for identifying the major classes of microsatellite loci in species for which few or no sequence data are available. AG/CT, AAG/CTT, ATG/CAT and GTG/CAC are the major motifs present in the Arabidopsis genome that can be used as convenient probes to isolate microsatellite loci by screening libraries. AAG/CTT is the more frequent of these motifs, and its relative frequency in Arabidopsis is much higher than averagely found in the plant kingdom. About 8% of the cDNA clones from an immature silique library contains AG/CT, AAG/CTT or ATG/CAT microsatellite loci. Several microsatellite loci were isolated by screening genomic and cDNA libraries. Twenty-six tri-nucleotide loci were PCR amplified from four different ecotypes, and polymorphism was observed for 12 of them; 10 loci showing two alleles and 2 loci showing three alleles.     

Development and characterization of microsatellite markers for an endangered shrub, <Emphasis Type="Italic">Ammopiptanthus mongolicus</Emphasis> (Leguminosae) and cross-species amplification in <Emphasis Type="Italic">Ammopiptanthus nanus</Emphasis>

We developed 11 polymorphic microsatellite markers for an endangered shrub Ammopiptanthus mongolicus using the Fast Isolation by AFLP of Sequences Containing repeats protocol. Polymorphism of each locus was assessed in 24 individuals from five natural populations of A. mongolicus. The average allele number of these markers was 4.2, ranging from 2 to 7. The observed (H _O) and expected (H _E) heterozygosities were 0.044–0.956 and 0.044–0.827, respectively. Further assessment in the congeneric species A. nanus revealed that nine of eleven loci were successfully amplified, but only two loci showed polymorphism. These markers provide powerful tools for the conservation genetics studies of A. mongolicus.     

Isolation and characterization of polymorphic microsatellite loci from a dinucleotide-enriched genomic library of spotted maigre (Nibea albiflora)

In the present study, we reported 13 polymorphic microsatellite loci isolated from a dinucleotide-enriched genomic library of Nibea albiflora. The number of alleles, observed and expected heterozygosity per locus in 44 individuals ranged from 2 to 13, from 0.0909 to 0.9773 and from 0.0886 to 0.9073, respectively. Three loci significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction. Analysis of linkage disequilibrium showed non-significant among the two pairs of loci. As a result, 13 microsatellite loci probably located on different chromosome pairs and these polymorphic microsatellite loci should provide sufficient level of genetic diversity to investigate the fine-scale population structure and evaluate the breeding strategy in Nibea albiflora. Shichao Xing, Changwei Shao contributed equally to this work.     

Isolation and characterization of polymorphic microsatellite loci from a dinucleotide-enriched genomic library of obscure puffer (Takifugu obscurus) and cross-species amplification

Obscure puffer (Takifugu obscurus) is an anadromous fish species in China. Here, we reported 10 polymorphic microsatellite loci isolated from a dinucleotide-enriched genomic library of T. obscurus. The number of alleles, observed and expected heterozygosity per locus in 30 individuals ranged from four to 10, from 0.57 to 0.86 and from 0.68 to 0.90, respectively. Three loci significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction and no significant linkage disequilibrium between pairs of loci was found. Cross-species amplification of these microsatellite loci in additional three fish species was performed. These polymorphic microsatellite loci would be useful for investigating genetic population structure and construction of genetic linkage map in T. obscurus.     

Isolation and characterization of polymorphic microsatellite loci from a dinucleotide-enriched genomic library of seven-band grouper (Epinephelus septemfasciatus) and cross-species amplification

Seven-band grouper (Epinephelus septemfasciatus) is a commercially important fishery species. Sixty-six microsatellite loci were isolated from a dinucleotide-enriched genomic library of E. septemfasciatus. Twelve of these loci were polymorphic in a test population with alleles per locus ranging from two to five, and observed and expected heterozygosities per locus from 0.04 to 1.00 and from 0.28 to 0.76, respectively. Three loci significantly deviated from Hardy–Weinberg equilibrium and no significant linkage disequilibrium was found between pairs of loci after Bonferroni correction. 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 E. septemfasciatus and other related species. Lili Zhao and Changwei Shao have contributed equally.