Nuclear microsatellite loci for Arabidopsis halleri (Brassicaceae), a model species to study plant adaptation to heavy metals

? Premise of the study: Arabidopsis halleri is a model species to study the adaptation of plants to soils contaminated by zinc, cadmium, and lead. To provide a neutral genetic background with which adaptive genetic markers could be compared, we developed highly polymorphic neutral microsatellite markers. ? Methods and Results: Using a microsatellite-enriched library method, we identified 120 microsatellite loci for quantitative trait locus (QTL) mapping analysis, of which eight primer pairs were developed in a single multiplex for population genetic studies. Analyses were performed on 508 individuals from 26 populations. All loci were polymorphic with six to 23 alleles per locus. Genetic diversity varied between 0.56 and 0.76. ? Conclusions: Our results demonstrated the value of these eight microsatellite markers to investigate neutral population genetic structure in A. halleri. To increase the resolution of population genetic analyses, we suggest adding them to the 11 markers previously developed independently.     

Development of microsatellite markers for the neotropical tree species Dipteryx alata (Fabaceae)

? Premise of the study: Microsatellite markers were developed for the population genetic analyses of the neotropical tree Dipteryx alata (Fabaceae). ? Methods and Results: Microsatellites were developed from a genomic shotgun library. Polymorphism at each microsatellite loci was analyzed based on 94 individuals from three populations. Eight loci amplified successfully and presented one to 10 alleles, and expected heterozygosities ranged from 0.097 to 0.862. Four loci also amplified in Pterodon emarginatus and presented similar polymorphism. ? Conclusion: The eight microsatellite primer pairs are potentially suitable for population genetic studies and successfully amplified in another Fabaceae species.     

The development of eight microsatellite loci in the wild daffodil Narcissus triandrus (Amaryllidaceae)

We report microsatellite primer pairs for the wild tristylous daffodil, Narcissus triandrus (Amaryllidaceae). From enriched libraries, we identified 58 unique microsatellite loci. We designed primer pairs for 27 of these loci and screened genomic DNA from 38 to 40 adults from a single population. For eight polymorphic loci, the number of alleles per locus ranged from five to 17. As six primers also amplified loci in three other Narcissus species, including two horticultural varieties, we expect that some of these markers will be transferable to other Narcissus species.     

Development of EST-SSR markers for Elaeocarpus photiniifolia (Elaeocarpaceae), an endemic taxon of the Bonin Islands

? Premise of the study: Expressed sequence tag (EST)-derived microsatellite markers were developed for Elaeocarpus photiniifolia, an endemic taxon of the Bonin Islands. ? Methods and Results: Initially, a complementary DNA (cDNA) library was constructed by de novo pyrosequencing of total RNA extracted from a seedling. A total of 267 primer pairs were designed from the library. Of the 48 tested loci, 25 loci were polymorphic among 41 individuals representing the entire geographical range of the species, with the number of alleles per locus and expected heterozygosity ranging from two to 14 and 0.09 to 0.86, respectively. Most loci were transferable to a related species, E. sylvestris. ? Conclusions: The developed markers will be useful for evaluating the genetic structure of E. photiniifolia.     

Isolation and characterization of microsatellite markers for a worldwide invasive weed, Chromolaena odorata (Asteraceae)

? PREMISE OF THE STUDY: Microsatellite loci were isolated and characterized for a worldwide invasive weed Chromolaena odorata (Asteraceae) to elucidate the population genetic structure and invasive history. ? MetHODS AND RESULTS: A total of 14 microsatellite primer pairs were developed using the Fast Isolation by AFLP of Sequences Containing repeats (FIASCO) protocol, and their polymorphism was assessed in two natural populations of C. odorata from Mexico and Trinidad and Tobago. Eleven loci showed polymorphism and eight of these loci were successfully amplified in Ageratina adenophora, another invasive weed related to C. odorata. ? CONCLUSIONS: These microsatellite markers are useful for investigating the population genetic structure and the history of range expansion of these invasive species.     

Microsatellite loci for Gossypium davidsonii (Malvaceae) and other D-genome, Sonoran Desert endemic cotton species

? Premise of the study: Microsatellite primers previously developed for domesticated cotton (Gossypium hirsutum; tetraploid) were screened for their utility in investigating genetic structure and gene flow within G. davidsonii and five other wild, Mexican, D-genome cotton species (all diploid). ? Methods and Results: We screened 50 microsatellite primer pairs from the Cotton Marker Database, identifying 10 loci as polymorphic within G. davidsonii. In genotyping approximately 200 individuals from four populations, we found that the number of alleles per locus ranged from seven to 17, and mean observed and expected heterozygosity ranged from 0.145 to 0.492 and from 0.436 to 0.734, respectively. We genotyped six to 20 individuals from each of the remaining species, finding these 10 loci to cross-amplify in all cases and in most cases to be polymorphic. ? Conclusions: These markers may be useful for further investigation of population genetics of G. davidsonii and other wild D-genome cotton species.     

Microsatellite markers for Grosmannia alacris (Ophiostomataceae, Ascomycota) and other species in the G. serpens complex

? Premise of the study: Polymorphic microsatellite markers were developed for the pine-infecting fungus, Grosmannia alacris. ? Methods and Results: Sixteen microsatellite markers were developed by using inter-simple sequence repeat (ISSR)-PCRs and 454 sequencing methods. Seven of these markers showed polymorphisms for a South African population of G. alacris, and 13 markers showed polymorphism when European isolates were included. Most of the primer pairs also amplified four closely related species: G. serpens, Leptographium gibbsii, L. castellanum, and L. yamaokae. ? Conclusions: These new markers will be useful for population studies of G. alacris and other species in the G. serpens complex.     

Development and characterisation of microsatellite markers for the medicinal plant Scutellaria baicalensis (Lamiaceae)

Scutellaria baicalensis is a popular medicinal plant that is on the verge of extinction due to uncontrolled harvesting, habitat destruction and deterioration of its ecosystem. We isolated and characterised 21 microsatellite loci in this species. Ninety-four individuals from six populations were used to test the polymorphism of the microsatellite loci. The number of alleles per locus ranged from 1 to 13, with a mean of 7.2. Observed and expected heterozygosities varied from 0.000 to 1.000 and 0.000 to 0.938, respectively. Among these new microsatellite markers, only two loci showed significant deviation from Hardy–Weinberg equilibrium. No locus pairs showed significant linkage disequilibrium. The 21 primer pairs were tested in other Scutellaria species. Most of these primer pairs worked successfully, except for Scut18. These new microsatellite markers could be applied to investigate the genetic diversity and population genetic structure of S. baicalensis and its closely related species.     

Efficiency of semi-automated fluorescent multiplex PCRs with 11 microsatellite markers for genetic studies of deer populations

Thirty bovine and eight ovine microsatellite primer pairs were tested on four tropical deer species: Eld's and Swamp deer (highly threatened) and Rusa and Vietnamese Sika deer (economically important). Thirty markers gave an amplified product in all four species (78.9%). The number of polymorphic microsatellite markers varied among the species from 14 in Eld's deer (47%) to 20 in Swamp deer (67%). Among them, 11 microsatellite loci were multiplexed in three polymerase chain reactions (PCRs) and labelled with three different fluorochromes that can be loaded in one gel-lane. To test the efficiency of the multiplex, primary genetic studies (mean number of alleles, expected heterozygosities and Fis values) were carried out on four deer populations. Parentage exclusion probability and probability of identity were computed and discussed on a Swamp deer population. These multiplexes PCRs were also tested on several other deer species and subspecies. The aim of this study is to establish a tool useful for genetic studies of population structure and diversity in four tropical deer species which with few modifications can be applied to other species of the genus Cervus.     

A novel set of microsatellite marker loci linkage-mapped in the house musk shrew, Suncus murinus.

Ten microsatellite DNA loci developed for the white-toothed shrew (Crocidura russula) were tested for PCR amplification and for utility in linkage studies in the house musk shrew, Suncus murinus. Four primer pairs successfully yielded PCR amplicons and showed polymorphism between two mutant strains, BAN-kc,oeb and WZ. Cloning and sequencing of the PCR amplicons of all the four loci confirmed the presence of microsatellite sequences. Alleles segregating in an F2 resource population constructed from the two strains ranged between two and five. Linkage analysis of the four loci together with 18 other polymorphic markers and three mutant loci resulted in five linkage groups containing three newly mapped microsatellite loci. This study reports the first microsatellite markers being registered in this species.     

Transferability of wheat microsatellites to diploid Aegilops species and determination of chromosomal localizations of microsatellites in the S genome.

Overall, 253 genomic wheat (Triticum aestivum) microsatellite markers were studied for their transferability to the diploid species Aegilops speltoides, Aegilops longissima, and Aegilops searsii, representing the S genome. In total, 88% of all the analyzed primer pairs of markers derived from the B genome of hexaploid wheat amplified DNA fragments in the genomes of the studied species. The transferability of simple sequence repeat (SSR) markers of the T. aestivum A and D genomes totaled 74%. Triticum aestivum-Ae. speltoides, T. aestivum-Ae. longissima, and T. aestivum-Ae. searsii chromosome addition lines allowed us to determine the chromosomal localizations of 103 microsatellite markers in the Aegilops genomes. The majority of them were localized to homoeologous chromosomes in the genome of Aegilops. Several instances of nonhomoeologous localization of T. aestivum SSR markers in the Aegilops genome were considered to be either amplification of other loci or putative translocations. The results of microsatellite analysis were used to study phylogenetic relationships among the 3 species of the Sitopsis section (Ae. speltoides, Ae. longissima, and Ae. searsii) and T. aestivum. The dendrogram obtained generally reflects the current views on phylogenetic relationships among these species.     

Rapid development of 36 polymorphic microsatellite markers for Tetranychus truncatus by transferring from Tetranychus urticae

Tetranychus truncatus Ehara is a phytophagous spider mite that is now one of the most important pests of agricultural and economic crops in East and Southeast Asia. However, population genetics and other studies of T. truncatus have been impeded by the lack of microsatellite markers, which are expensive and time-consuming to identify. Previous studies indicated a high potential of cross-amplification of microsatellites in Tetranychus species, meaning that the microsatellite flanking sequences are sufficiently homologous among Tetranychus species that the primers for one species may work in another species. Here, we tested 205 primer pairs designed from the whole genome sequence of Tetranychus urticae Koch, a sister species of T. truncatus, for microsatellite markers in three populations of T. truncatus in China (N = 94). About half (102) of these primer pairs yielded the desired PCR products, 36 of which revealed polymorphism in T. truncatus. Each of the 36 markers harbored between 2 and 23 alleles, with a mean polymorphic information content of 0.589 (0.119–0.922 range). The mean observed and expected heterozygosity across loci and the three populations were 0.468 and 0.628, respectively. Of the 36 primer pairs, 22 also worked in Tetranychus piercei, but only a few of them worked in T. ludeni and T. phaselus. Cross-amplification is thus a cost-effective way to develop microsatellite markers, which can be of great value in population genetics studies.     

The use of microsatellites for detecting DNA polymorphism, genotype identification and genetic diversity in wheat

A set of 20 wheat microsatellite markers was used with 55 elite wheat genotypes to examine their utility (1) in detecting DNA polymorphism, (2)in the identifying genotypes and (3) in estimating genetic diversity among wheat genotypes. The 55 elite genotypes of wheat used in this study originated in 29 countries representing six continents. A total of 155 alleles were detected at 21 loci using the above microsatellite primer pairs (only 1 primer amplified 2 loci; all other primers amplified 1 locus each). Of the 20 primers amplifying 21 loci, 17 primers and their corresponding 18 loci were assigned to 13 different chromosomes (6 chromosomes of the A genome, 5 chromosomes of the B genome and 2 chromosomes of the D genome). The number of alleles per locus ranged from 1 to 13, with an average of 7.4 alleles per locus. The values of average polymorphic information content (PIC) and the marker index (MI) for these markers were estimated to be 0.71 and 0.70, respectively. The (GT)_n microsatellites were found to be the most polymorphic. The genetic similarity (GS) coefficient for all possible 1485 pairs of genotypes ranged from 0.05 to 0.88 with an average of 0.23. The dendrogram, prepared on the basis of similarity matrix using the UPGMA algorithm, delineated the above genotypes into two major clusters (I and II), each with two subclusters (Ia, Ib and IIa, IIb). One of these subclusters (Ib) consisted of a solitary genotype (E3111) from Portugal, so that it was unique and diverse with respect to all other genotypes belonging to cluster I and placed in subcluster Ia. Using a set of only 12 primer pairs, we were able to distinguish a maximum of 48 of the above 55 wheat genotypes. The results demonstrate the utility of microsatellite markers for detecting polymorphism leading to genotype identification and for estimating genetic diversity. Received: 15 May 1999 / Accepted: 27 July 1999     

Isolation and mapping of microsatellite markers specific for the D genome of bread wheat.

The potential of Aegilops tauschii, the diploid progenitor of the D genome of wheat, as a source of microsatellite markers for hexaploid bread wheat was investigated. By screening lambda phage and plasmid libraries of Ae. tauschii genomic DNA, dinucleotide microsatellites containing GA and GT motifs were isolated and a total of 65 functional microsatellite markers were developed. All primer pairs that were functional in Ae. tauschii amplified well in hexaploid wheat. Fifty-five loci amplified by 48 primer sets were placed onto a genetic framework map of the reference population of the International Triticeae Mapping Initiative (ITMI) 'Opata 85' x 'W7984'. The majority of microsatellite markers could be assigned to the chromosomes of the D genome of wheat. The distribution of the markers along the chromosomes is random. Chromosomal location of 22 loci nonpolymorphic in the reference population was determined using nullitetrasomic lines of Triticum aestivum 'Chinese Spring'. The results of this study demonstrate the value of microsatellite markers isolated from Ae. tauschii for the study of bread wheat. The microsatellite markers developed improve the existing wheat microsatellite map and can be used in a wide range of genetic studies and breeding programs.     

Isolation and characterization of microsatellite loci in the endangered tree Diplopanax stachyanthus (Araliaceae)

? Premise of the study: Microsatellite markers were developed in Diplopanax stachyanthus to investigate the population genetics of this endangered tree. ? Methods and Results: Using the Fast Isolation by AFLP of Sequences Containing repeats (FIASCO) protocol, 15 microsatellite markers were developed in D. stachyanthus and evaluated for their variability in 25 samples from a natural population. For the 11 polymorphic loci, the number of alleles ranged from two to eight, while the observed and expected heterozygosities ranged from 0.5200 to 0.7600 and 0.4200 to 0.7813, respectively. Their cross-taxa transferability was also examined in Acanthopanax gracilistylus, Tetrapanax papyrifer, Cornus controversa, and Dendrobenthamia japonica var. chinensis, and four to 15 loci proved amplifiable in these species. ? Conclusions: These microsatellite markers could be employed to investigate the population genetics of D. stachyanthus, and may potentially be applicable to other related species.     

Design and implementation of degenerate microsatellite primers for the mammalian clade

Microsatellites are popular genetic markers in molecular ecology, genetic mapping and forensics. Unfortunately, despite recent advances, the isolation of de novo polymorphic microsatellite loci often requires expensive and intensive groundwork. Primers developed for a focal species are commonly tested in a related, non-focal species of interest for the amplification of orthologous polymorphic loci; when successful, this approach significantly reduces cost and time of microsatellite development. However, transferability of polymorphic microsatellite loci decreases rapidly with increasing evolutionary distance, and this approach has shown its limits. Whole genome sequences represent an under-exploited resource to develop cross-species primers for microsatellites. Here we describe a three-step method that combines a novel in silico pipeline that we use to (1) identify conserved microsatellite loci from a multiple genome alignments, (2) design degenerate primer pairs, with (3) a simple PCR protocol used to implement these primers across species. Using this approach we developed a set of primers for the mammalian clade. We found 126,306 human microsatellites conserved in mammalian aligned sequences, and isolated 5,596 loci using criteria based on wide conservation. From a random subset of ~1000 dinucleotide repeats, we designed degenerate primer pairs for 19 loci, of which five produced polymorphic fragments in up to 18 mammalian species, including the distinctly related marsupials and monotremes, groups that diverged from other mammals 120-160 million years ago. Using our method, many more cross-clade microsatellite loci can be harvested from the currently available genomic data, and this ability is set to improve exponentially as further genomes are sequenced.     

Isolation and characterization of microsatellites in Brassica rapa L

We report here the isolation and characterization of microsatellites, or simple sequence repeats (SSRs), in Brassica rapa. The size-fractionated genomic library was screened with (GA)(15) and (GT)(15) oligonucleotide probes. A total of 58 clones were identified as having the microsatellite repeats, and specific primer pairs were designed for 38 microsatellite loci. All primer pairs, except two, amplified fragments having the sizes expected from the sequences. Of the 36 primer pairs, 35 amplified polymorphic loci in 19 cultivars of B. rapa, while monomorphism was observed in only one primer pair. A total of 232 alleles was identified by the 36 primer pairs in 19 cultivars of B. rapa, and these primer pairs were examined also in nine Brassicaceae species. Most of the 36 primer pairs amplified the loci in the Brassicaceae species. Segregation of the microsatellites was studied in an F(2) population from a cross of doubled-haploid lines DH27 x G309. The microsatellites segregated in a co-dominant manner. These results indicate that the microsatellites isolated in this study were highly informative and could be useful tools for genetic analysis in B. rapa and other related species.     

海南龙血树种群生境及自然更新能力调查

对海南岛海南龙血树(Dracaena cambodiana Pierre ex Gagnep)生境、人为破坏情况和自然更新能力进行了调查与分析,探讨了其濒危原因。结果表明,海南龙血树属典型的岩石伴生型植物,主要分布在高温少雨地区,常生长在陡峭且裸露的花岗岩或石灰岩的石缝残积土中,或紧贴石壁生长于砂壤土中,其伴生树种以小乔木或灌木为主;由于无节制采挖和生境破坏,海南龙血树野生资源数量已十分有限。自然条件下海南龙血树的更新方式有种子更新、根蘖更新和桩蘖更新,但现有生境条件下无论何种更新方式均无法有效地实现种群的扩大和更新。可见,原生境破坏和无节制采挖是海南龙血树濒危的外因,"濒危生境"造成种子无法萌发或幼苗生长失败,导致种群无法实现自然更新是内因和主要原因。