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Invasions can be genetically diverse, and that diversity may have implications for invasion management in terms of resistance or tolerance to control methods. We analyzed the population genetics of Russian-olive (Elaeagnus angustifolia L.), an ecologically important and common invasive tree found in many western U.S. riparian areas. We found three cpDNA haplotypes and, using 11 microsatellite loci, identified three genetic clusters in the 460 plants from 46 populations in the western United States. We found high levels of polymorphism in the microsatellites (5 to 15 alleles per locus; 106 alleles total). Our native-range sampling was limited, and we did not find a genetic match for the most common cpDNA invasive haplotype or a strong confirmation of origin for the most common microsatellite genetic cluster. We did not find geographic population structure (isolation by distance) across the U.S. invasion, but we did identify invasive populations that had the most diversity, and we suggest these as choices for initial biological control–release monitoring. Accessions from each genetic cluster, which coarsely represent the range of genetic diversity found in the invasion, are now included in potential classical biological control agent efficacy testing.
The plerocercoid (sparganum) of Spirometra erinaceieuropaei is the main aetiological agent of human sparganosis. To improve the current knowledge on S. erinaceieuropaei evolution, we performed multi-locus microsatellite typing of sparganum isolates from China for the first time. All available expressed sequence tag (EST) sequences for the Spirometra were downloaded from the GenBank. The identification and localization of microsatellites in ESTs was accomplished by MISA. Based on the selected microsatellites, the genetic structure of 64 sparganum isolates collected from 11 geographical locations in southwest China were investigated through principal component analysis, STRUCTURE analysis and neighbour-joining clustering. A total of 522 non-redundant ESTs containing 915 simple sequence repeats were identified from 12 481 ESTs screened. Five primer pairs were finally selected. Using these loci, a total of 12 alleles were detected in 64 sparganum isolates. Little variability was observed within each of geographical population, especially among isolates derived from Kunming of Yunnan (YN-KM) province. Both STRUCTURE analysis and the clustering analysis supported that two genotypes existed among the sparganum isolates from southwest China. In conclusion, five microsatellite markers were successfully developed, and sparganum population was observed to harbour low genetic variation, further investigation with deeper sampling was needed to elucidate the population structure.
Camellia oleifera is an important woody plant producing healthy edible oils. People need a large number of molecular markers, especially microsatellite, in breeding of C. oleifera. In this study, we sequenced the root transcriptomes of C. oleifera, and then designed a novel set of microsatellite markers based on the root-expressed genes. We assembled a total of 57,121 unigenes with a length of 42.63 Mb, which harboured 15,902 microsatellites. Among these microsatellites, di-nucleotide repeat motifs were the most abundant group (56.45%), then followed by tri- (25.20%), mono- (12.12%), hexa- (3.21%), penta- (2.18%) and quad-nucleotide ones (0.84%). In total, 6738 primer pairs were designed successfully to amplify the microsatellite loci. To test these microsatellite markers, 48 primer pairs were randomly selected and synthesized and validated in C. oleifera and its eight relatives. Up to 75% of the primer pairs amplified in C. oleifera and its relatives, and 62.5% displayed polymorphism. The transferability and diverse alleles across its eight relatives were detected for each polymorphic primer pair. The novel set of microsatellites derived from the root transcriptomes here provided a useful resource for future molecular genetics improvement of C. oleifera and its relatives.
The genus Narcissus L. (Amaryllidaceae) provides a model system to study the evolution and maintenance of sexual polymorphisms. In this study, we characterized microsatellite markers for N. dubius, N. cuatrecasasii, N. assoanus and N. rupicola for studies of genetic diversity and paternity analyses to investigate the stability of stylar dimorphism. We proved 40 new primer pairs from a genomic library of N. papyraceus and 12 microsatellite markers characterized also for N. papyraceus in a previous study (52 primer pairs overall). Twenty markers amplified, but their transferability and variability were different among species. Polymorphism was tested at least on 74 individuals and one population per species. The number of polymorphic loci per species ranged from four to eight. The number of alleles per locus ranged from two to 19 and the observed heterozygosity and gene diversity, from 0.107 to 0.729 and 0.103 to 0.894, respectively. These markers can be used for studies of genetic diversity and paternity analyses among individuals of N. dubius, N. cuatrecasasii, N. assoanus and N. rupicola to study the stability of stylar dimorphism.
Digitaria exilis is an important indigenous cereal in West Africa. The first fonio reference transcriptome was released and became a key tool for developing new molecular markers contributing to a better understanding of its genetic diversity. A total of 126 new putative primer pairs were successfully designed in 37,327 unigenes from the D. exilis transcriptome. Thirty-seven primer pairs were randomly selected and tested for their ability to cross-amplify to related species. Clear amplification patterns were observed on 24 primer pairs. Of these, 71, 74 and 35% showed polymorphism in three species: D. exilis, D. longiflora and D. iburua. The transferability from D. exilis was 96% to D. longiflora and 71% to D. iburua. The new SSR markers confirmed the close genetic proximity of D. exilis with D. longiflora and its stronger genetic difference of D. exilis from D. iburua. These markers will be valuable for completing future knowledge on Digitaria evolutionary history, and for testing gene flows between related species.
The white-backed planthopper, Sogatella furcifera (Horváth) (Hemiptera, Delphacidae), has emerged as a serious rice pest in Asia. In the present study, 12 microsatellite markers were employed to investigate the genetic structure, diversity and migration route of 43 populations sampled from seven Asian countries (Bangladesh, China, Korea, Laos, Nepal, Thailand, and Vietnam). According to the isolation by distance analysis, a significant positive correlation was observed between genetic and geographic distances by the Mantel test (r2 = 0.4585, P = 0.01), indicating the role of geographic isolation in the genetic structure of S. furcifera. A population assignment test using the first-generation migrants detection method (thresholds a = 0.01) revealed southern China and northern Vietnam as the main sources of S. furcifera in Korea. Nepal and Bangladesh might be additional potential sources via interconnection with Vietnam populations. This paper provides useful data for the migration route and origin of S. furcifera in Korea and will contribute to planthopper resistance management.
We developed novel and polymorphic microsatellite primers for Spathoglottis plicata, a tropical and subtropical terrestrial orchid, to investigate the genetic patterns and population structure among wild populations, and also to identify the varieties and hybrids of S. plicata in horticultural industry. The 12 novel microsatellites from S. plicata were developed by using polymerase chain reaction (PCR)-based isolation of microsatellite arrays. These markers that were successfully PCR amplified exhibited polymorphisms in S. plicata. The number of alleles, observed heterozygosity, expected heterozygosity and polymorphism information content values across loci ranged from 2.000 to 8.000, 0.000 to 0.756, 0.208 to 0.813 and 0.405 to 0.805 in total populations, respectively. The newly developed microsatellite markers exhibited variation in S. plicata. These markers can be used as a tool to further investigate the genetic diversity, conservation genetics and variety/hybrid identification of S. plicata.
Genome sequencing has greatly contributed to our understanding of parasitic protozoa. This is particularly the case for Cryptosporidium species (phylum Apicomplexa) which are difficult to propagate. Because of their polymorphic nature, simple sequence repeats have been used extensively as genotypic markers to differentiate between isolates, but no global analysis of amino acid repeats in Cryptosporidium genomes has been reported. Taking advantage of several newly sequenced Cryptosporidium genomes, a comparative analysis of single-amino-acid repeats (SAARs) in seven species was undertaken. This analysis revealed a striking difference between the SAAR profile of the gastric and intestinal species which infect mammals and one species which infects birds. In average, total SAAR length in gastric species is only 25% of the cumulative SAAR length in the genome of Cryptosporidium parvum, Cryptosporidium hominis and Cryptosporidium meleagridis, species infectious to humans. The SAAR profile in the avian parasite Cryptosporidium baileyi stands out due to the presence of long asparagine repeats. Cryptosporidium baileyi proteins with repeats ⩾20 residues are significantly enriched in regulatory functions. As postulated for the related apicomplexan species Plasmodium falciparum, these observations suggest that Cryptosporidium SAARs evolve in response to selective pressure. The putative selective mechanisms driving SAAR evolution in Cryptosporidium species are unknown.
Compared with conventional identification methods, DNA-based genetic approaches such as single nucleotide polymorphisms (SNPs) and satellites are much more reliable for pig identification and meat traceability. In this study, multiallelic amplification fragments with multiple SNPs, incorporating the advantages of both SNPs and microsatellites, were explored for the first time for pig identification and meat traceability. Primer pairs for multiallelic fragments and their optimal SNPs were successfully selected and used for identification of individuals from Suzhong and Duroc populations. Meanwhile, the combined panel of the above mentioned primer pairs together with their optimal SNPs for Suzhong and/or Duroc pigs were validated for identification of the hybrids (Suzhong×Duroc). Therefore, we have successfully selected multiallelic amplification fragments with multiple SNPs to identify pigs and their meat samples from Suzhong, Duroc or their hybrids. Our study demonstrates that our method is more powerful for pig identification or meat traceability than SNPs or microsatellites.
The major histocompatibility complex region has been implicated in explaining some of the variation observed in adaptability and tick susceptibility of cattle. The bovine leukocyte antigen region of 192 cattle representing indigenous, composite and exotic breeds used in commercial beef production in Namibia and South Africa was investigated using four microsatellite markers. Ticks counted under the tail were taken as an indicator of tick susceptibility. Tick scores of all but one population was low (11 to 20 ticks), with only the South African Bonsmara population having an average score of 31 to 40 ticks per animal. The observed variation based on four microsatellite markers ranged from 5.5 alleles in Namibian Afrikaner to 7.7 alleles in South African Nguni and Bonsmara cattle. Unbiased heterozygosity values ranged from 0.66 (Namibian Afrikaner) to 0.76 (South African Bonsmara). Structure analyses grouped the five populations into three indistinct clusters with limited genetic variation between the populations.
Adélie penguins (Pygoscelis adeliae) are responding to ocean–climate variability throughout the marine ecosystem of the western Antarctic Peninsula (WAP) where some breeding colonies have declined by 80%. Nuclear and mitochondrial DNA (mtDNA) markers were used to understand historical population genetic structure and gene flow given relatively recent and continuing reductions in sea ice habitats and changes in numbers of breeding adults at colonies throughout the WAP. Genetic diversity, spatial genetic structure, genetic signatures of fluctuations in population demography and gene flow were assessed in four regional Adélie penguin colonies. The analyses indicated little genetic structure overall based on bi-parentally inherited microsatellite markers (FST =-0.006–0.004). No significant variance was observed in overall haplotype frequency (mtDNA ΦST =0.017; P=0.112). Some comparisons with Charcot Island were significant, suggestive of female-biased philopatry. Estimates of gene flow based on a two-population coalescent model were asymmetrical from the species’ regional core to its northern range. Breeding Adélie penguins of the WAP are a panmictic population and hold adequate genetic diversity and dispersal capacity to be resilient to environmental change.
Understanding the impact of altitude and ecological heterogeneity at a fine scale on the populations of malaria vectors is essential to better understand and anticipate eventual epidemiological changes. It could help to evaluate the spread of alleles conferring resistance to insecticides and also determine any increased entomological risk of transmission in highlands due to global warming. We used microsatellite markers to measure the effect of altitude and distance on the population genetic structure of Anopheles funestus and Anopheles gambiae s.s. in the Muheza area in the north-eastern part of Tanzania (seven loci for each species). Our analysis reveals strong gene flow between the different populations of An. funestus from lowland and highland areas, as well as between populations of An. gambiae sampled in the lowland area. These results highlight for An. funestus the absence of a significant spatial subpopulation structuring at small-scale, despite a steep ecological and altitudinal cline. Our findings are important in the understanding of the possible spread of alleles conferring insecticide resistance through mosquito populations. Such information is essential for vector control programmes to avoid the rapid spread and fixation of resistance in mosquito populations.
Salers are a native French breed used for beef and dairy production that has expanded to all the continents. The Salers breed was introduced to the north of Spain in 1985 with only 15 individuals from France and has successfully increased to over 20 000 animals. Although over time new animals have been imported from France for breeding, it is possible that the limiting number of founder animals could have resulted in a reduction of the genetic diversity found in Spanish Salers. Thus, the purpose of the present study has been to characterize the genetic diversity of Salers breed in Spain and evaluate a possible founder effect due to reduced number of the first reproducers. A total of 403 individuals from 12 Salers herds were analyzed using 12 microsatellite markers and compared with phylogenetically and geographically close related Blonde d’Aquitaine, Limousin and Charolais French breeds but also other 16 European breeds. Microsatellites in Salers were polymorphic, with a mean allelic richness of 5.129 and an expected heterozygosity of 0.621 across loci (0.576 to 0.736 among all breeds). Average observed heterozygosity was 0.618. All the loci fit the Hardy–Weinberg (HW) equilibrium except TGLA227 locus due to a significant deficit of heterozygotes in only one of the herds, probably attributable to a sampling effect. When all loci were combined, Salers inbreeding coefficient did not differ statistically from 0 (FIS=0.005), indicating not significant excess or deficit of heterozygotes (P=0.309). Based in allelic distribution, Salers revealed a frequency of 0.488 in BM2113-131 and 0.064 in BM2113-143 diagnostic alleles, which are specific to the African zebu. These zebu alleles are also found in some French breeds, supported by STR data previously postulated hypothesis of a migration route through Mediterranean route by which North African cattle may have left a genetic signature in southern Europe. Phylogenetic tree and population structure analyses could unambiguously differentiate Salers cattle from the other populations and 10% of the total genetic variability could be attributed to differences among breeds (mean RST=0.105; P<0.01). Mutation-drift equilibrium tests (sign test and Wilcoxon’s sign rank test) were in correspondence to the absence of founder effect when Bonferroni was applied. Gene diversity previously reported in French Salers was comparable with the observed in our population. Thus, high genetic diversity in Spanish Salers highlights the resources of this population, which looks toward future breeding and selection programs.
The southern harvester termite, Microhodotermes viator, is ecologically important due to its nutrient cycling activities and trophic interactions. Additionally, M. viator appears to have very long-lived colonies, which amplifies their effect on the environment. In order to estimate the longevity of a colony it is necessary to understand colony genetic structure. However, intra- and intercolonial genetic structure and levels of relatedness have not yet been examined in this species, likely due to a lack of microsatellite markers that effectively hybridize in this species. Here we describe the identification and characterization of seven microsatellite loci for M. viator, using an enriched approach and a preliminary test of their suitability for studies of fine-scale population genetic structure. Seven polymorphic loci were identified, none of which deviated from Hardy–Weinberg equilibrium. The loci had an average of 5.8 alleles per locus (range: 2–14) and an overall mean heterozygosity of 0.51 ± 0.3. Across all loci, population level pairwise FST values showed significant genetic differentiation. The loci described and preliminary genetic data presented here provide an invaluable tool for future studies of population structure and longevity in M. viator colonies.
The greater one-horned rhinoceros Rhinoceros unicornis is a flagship species for conservation in protected areas in India and Nepal. In India the species is afforded the highest level of legal protection under Schedule I of the Wildlife (Protection) Act 1972. Although censuses of greater one-horned rhinoceros have been carried out for decades using the traditional total count method, no advanced scientific approach has been adopted for population estimation of the species in India or elsewhere. We optimized noninvasive genetic techniques for identification of greater one-horned rhinoceros from dung samples, and applied these to estimate the number of rhinoceros in Gorumara National Park, in West Bengal, India. Our results confirmed the presence of 43 individuals from 60 dung samples collected throughout the Park in 2011. We confirmed a male-to-female sex ratio of 3.8 : 1, based on analysis of DNA from dung samples, using a y-chromosome linked marker. Our results are in concordance with a census carried out by the West Bengal Forest Department that found 42 rhinoceros in the Park, with a male-to-female sex ratio of 3.5 : 1. Our study thus demonstrates the feasibility of using a noninvasive genetic approach for population estimation of greater one-horned rhinoceros in the wild.
While Liriomyza sativae (Diptera: Agromyzidae), an important invasive pest of ornamentals and vegetables has been found in China for the past two decades, few studies have focused on its genetics or route of invasive. In this study, we collected 288 L. sativae individuals across 12 provinces to explore its population genetic structure and migration patterns in China using seven microsatellites. We found relatively low levels of genetic diversity but moderate population genetic structure (0.05 < FST < 0.15) in L. sativae from China. All populations deviated significantly from the Hardy–Weinberg equilibrium due to heterozygote deficiency. Molecular variance analysis revealed that more than 89% of variation was among samples within populations. A UPGMA dendrogram revealed that SH and GXNN populations formed one cluster separate from the other populations, which is in accordance with STRUCTURE and GENELAND analyses. A Mantel test indicated that genetic distance was not correlated to geographic distance (r = −0.0814, P = 0.7610), coupled with high levels of gene flow (M = 40.1–817.7), suggesting a possible anthropogenic influence on the spread of L. sativae in China and on the effect of hosts. The trend of asymmetrical gene flow was from southern to northern populations in general and did not exhibit a Bridgehead effect during the course of invasion, as can be seen by the low genetic diversity of southern populations.
This is the first report of microsatellite markers (simple sequence repeats, SSR) for fall webworm, Hyphantria cunea (Drury) (Lepidoptera: Arctiidae), an important quarantine pest in some European and Asian countries. Here, we developed 48 microsatellite markers for H. cunea from SSR enrichment libraries. Sequences isolated from libraries were sorted into four categories and analyzed. Our results suggest that sequences classified as Grouped should not be used for microsatellite primer design. The genetic diversity of microsatellite loci was assessed in 72 individuals from three populations. The number of alleles per locus ranged from 2 to 5 with an average of 3. The observed and expected heterozygosities of loci ranged from 0 to 0.958 and 0 to 0.773, respectively. A total of 18 out of 153 locus/population combinations deviated significantly from Hardy–Weinberg equilibrium. Moreover, significant linkage disequilibrium was detected in one pair of loci (1275 pairs in total). In the neutral test, two loci were grouped into the candidate category for positive selection and the remainder into the neutral category. In addition, a complex mutation pattern was observed for these loci, and FST performed better than did RST for the estimation of population differentiation in different mutation patterns. The results of the present study can be used for population genetic studies of H. cunea.
Since the immediate wild relatives of Sorghum bicolor (L.) Moench are indigenous to Ethiopia, studying their population biology is timely for undertaking conservation measures. A study was conducted to investigate the occurrence of population bottlenecks and to estimate the long-term effective population size (Ne) in wild relatives of sorghum. For this, 40 samples of wild sorghum were collected from two remotely located populations that were allopatric to the cultivated sorghum. The presence of bottlenecks was investigated using heterozygosity excess/deficiency, mode shift and allelic diversity based on nine polymorphic simple sequence repeat (SSR) loci. We also estimated the Ne of the studied populations using two different methods employing SSR mutation models. The expected heterozygosity was found to be 0.41 and 0.71 and allelic richness was 3.0 and 4.9, in Awash and Gibe populations, respectively. Neither the heterozygosity excess nor the mode-shift methods detected signatures of bottlenecks in the studied populations. The effective size of the two wild sorghum populations studied also showed no risk of population reduction in these regions of Ethiopia. Therefore, these allopatric wild sorghum populations can survive by occupying patches by the roadsides and fences, areas within abandoned farm lands, forests, etc., which shows that their wild characteristics of adaptation have been adequate for them to survive from extinction despite extensive deforestation of their habitat for modern agriculture and frequent grazing by livestock. However, this does not guarantee the survival of these species for the future and ex situ conservation measures or policies could help maintain their diversity.
Microsatellite markers specific to Cheirostylis yunnanensis Rolfe were developed using an enriched genomic DNA library technique. The library was constructed using (AG)20 and (CAG)20 oligonucleotide repeats. A total of 48 primer pairs were designed and tested with 48 C. yunnanensis Rolfe samples, resulting in 11 polymorphic loci. The number of alleles per locus ranged from 2 to 12, with an average of six alleles. The observed and expected heterozygosity ranged from 0.0426 to 0.8085 and 0.0421 to 0.9078, respectively. Of the 11 polymorphic loci, three showed a significant deviation from Hardy–Weinberg equilibrium and one exhibited linkage disequilibrium. Cross-species amplification was tested with five samples of Cheirostylis of unknown species resulting in eight loci that could be amplified, with the number of alleles ranging from one to two. The microsatellite markers developed in this study will be useful for the genetic analysis of C. yunnanensis in order to differentiate species as well as to establish a conservation plan for this species.
Sustainable development of a breeding programme depends on having sufficient genetic variability to achieve genetic gains in each selection cycle. The aim of this study was to molecularly characterize families of the oil palm, Elaeis guineensis Jacq., of different origins using microsatellite molecular markers. The value of the observed heterozygosity was higher than that of the expected heterozygosity in all of the progenies. The coefficients (GST= 0.207 and FST= 0.174) and AMOVA showed genotypic differences among the evaluated families. Likewise, this was reflected in the groups obtained by the dendrogram and principal coordinate analyses. This difference could have evolved due to the enrichment of some of the families with germplasm from different origins. Therefore, genetic relationships estimated from molecular data would be convenient to select families more distant from each group and palms more distant from each family selected to reserve genetic variability. This information will guide us in the decision-making process when planning breeding programmes focused on crosses to develop new populations with an acceptable broad genetic base and adaptability. In this way, sources of resistance to biotic and abiotic factors can be identified for the development of new varieties with competitive advantages for the sector.