Heterozygosity Deficit Research Articles

Genetic Polymorphism of g.3768T>C loci of NRAMP1 gene in Kampung and KUB Chickens

Natural Resistance-Associated Macrophage Protein 1 (NRAMP1) is a gene that regulates the body's resistance to illness. The genetic diversity of Kampung and KUB chicken population in Lombok island West Nusa Tenggara province was investigated based on g.3768T>C loci of NRAMP1 gene. Experimental animal consisted of 105 KUB and 67 Kampung chickens. The NRAMP1 gene polymorphisms in both population were identified using PCR-RFLP method. Genetic parameters of g.3768T>C loci were calculated using PopGene32. In this study, the locus g.3768T>C of the NRAMP1gene found three genotypes (TT, CT, CC) with the frequency of the C allele was higher than the T allele, respectively 0.709 and 0.210 in Kampung chicken, and 0.738 and 0.262 in KUB chicken. The mean value of observed heterozygosity (Ho) and expected heterozygosity (He) of g.3768T>C loci in both populations revealed low to medium genetic diversity, with the values 0.222 and 0.400, respectively. The mean value of observed heterozygosity is lower than expected, indicating that the population is heading towards a heterozygosity deficit and proving that the two populations are not in Hardy-Weinberg equilibrium. The mean PIC value of the NRAMP1 gene (g.3768T>C) in both chicken population was 0.319 and classified as fairly informative (0.50 > PIC > 0.25). Meanwhile, the value of the genetic differentiation index (Fst) for Kampung and KUB chicken population were 0.385 and 0.433, indicating that there is differentiation between two chicken population at the observed loci.

Genetic Diversity in Katchaikatty Sheep based on Microsatellites Polymorphism

Background: Sheep is one of the important species of livestock in India contributing to meat production. India has 44 distinct breeds of sheep, out of which 10 are found in Tamil Nadu. The present study describes the molecular characterization of recently registered breed of sheep - Katchaikatty sheep, genetic variability and genetic structure of the population by microsatellite marker analyses. Methods: DNA from 50 unrelated Katchaikatty sheep was amplified with 25 FAO recommended fluorescent tagged ovine-specific microsatellite markers and genotyped on an automated Genetic Analyzer. In each locus, observed (no) and effective number of microsatellite alleles (ne), allele frequencies, observed (Ho) and expected (He) heterozygosity and heterozygosity deficit estimate (FIS), polymorphism information content (PIC) and Chi-square (χ2) test for Hardy-Weinberg equilibrium (HWE) were assessed. Mode-shift analyses were performed. Result: The study revealed a total of 144 alleles across all the loci. The number of alleles at each locus varied from one to 10 with a mean of 5.76 alleles. The PIC values in the microsatellite loci ranged from 0.34 (OarAE129) to 0.83 (OarFCB48) with an average of 0.59, which showed a high genetic polymorphism. Six out of 25 microsatellite loci studied were in Hardy-Weinberg equilibrium and 19/25 loci showed positive FIS values. The overall mean observed and expected heterozygosity were 0.50 and 0.65 respectively and the estimates elucidated a substantial genetic variability in Katchaikatty sheep population. Mode shift analysis revealed a normal L-shaped curve, describing that the Katchaikatty population had not experienced any genetic bottleneck and remained in mutation-drift equilibrium.

Investigating growth associated genomic short tandem repeats (STRs) in a resource population generated through molecular breeding of RIR chicken

The long-term selection based on phenotypes causes loss of variation in performance traits and slows down the genetic progress per generation in the population; genomic selection could restore the variability along with faster genetic progress. Genomic short tandem repeats (STRs) in a resource population of RIR chicken were explored investigating randomly selected 114 pedigreed chicks. Alleles separated through 3.4% MetaPhor agarose gel electrophoresis at ten STR loci, and data recorded on growth traits were analyzed. Twenty-six alleles were resolved with frequencies of 0.1140–0.7632 and > 38.60% for the most frequent alleles at ten STR loci. The most frequent genotypes appeared with frequency >21.93% at different loci. Polymorphic information contents ranged from 0.2961 (LEI0079) to 0.6716 (LEI0071). Effective number of alleles ranged from 1.5662 (LEI0079) to 3.5836 (LEI0071). Mean FIS statistics revealed overall 21.78% heterozygosity deficit. Average heterozygosity ranged from 0.3630 (LEI0079) to 0.7241 (LEI0071). Chi-square and G-square test showed the population in Hardy-Weinberg disequilibrium at nine loci. Chick weight was significantly influenced by the factor of sire, and body weight traits by sex and hatch factors of the birds coded with STR-genotypes. ADL0328-BB genotype had the highest chick weight. LEI0068-BC and LEI0071-CC genotypes showed maximum 28-weeks body weight. MCW0010-AA genotype had the potential bearing of the highest body weight records at 16, 32, 36 and 40 weeks of age. MCW0058-CC genotype revealed the same at 24 and 28 weeks of age. The study impacts on marker assisted selection program for genetic improvement of growth traits in poultry.

Sample contamination explains evidence of close kin proximity in yellowfin tuna (Thunnus albacares) in the Western and Central Pacific Ocean

Anderson et al.’s 2019 paper ‘Close Kin Proximity in Yellowfin Tuna (Thunnus albacares) as a Driver of Population Genetic Structure in the Tropical Western and Central Pacific’ provided observations of genetically related individuals among sampled yellowfin tuna. Resampling of some individuals from the original study produced very different sequencing results when compared with the original dataset, one possible explanation of which is cross-contamination among the original samples. Re-analyses produced no indication of strong population structure, including a very slightly and consistent heterozygosity deficit with only one statistically significant pairwise FST value of 0.002. We identified only one pair of genetically similar individuals that could still be an artefact of lingering contamination. These new results therefore support a highly connected population of yellowfin tuna in the study area, although we do not rule out the potential for local adaptation driven by non-observed loci or genetic sub-structure operating at more contemporary scales.

Genetic Diversity of Yuca (Manihot esculenta esculenta; Cassava, Manioc), an Indigenous Crop in the Peruvian Amazon

Yuca (Manihot esculenta esculenta; cassava, manioc) is a native Amazonian crop represented by myriad landraces. To investigate human influences on its diversification, we conducted field observations and analyzed 13 short tandem repeat (STR) loci in 43 landraces in the Peruvian Amazon. We found a different multilocus genotype (MLG) in every landrace. However, tests for Hardy–Weinberg equilibrium found a deficit of heterozygosity at every locus (p < 0.001 for 12 of 13 loci). Further, the fraction of genetic variance due to landrace differences was greater than expected (38.84%; p = 0.001). This suggested that landrace hybridization is restricted, a finding consistent with our field observations. However, we found an excess of within-landrace heterozygosity (p < 0.001) in 39 of 43 landraces, suggesting they originated through hybridization. Mantel tests identified associations between genetic and geographic distances (p < 0.001), but their correlation coefficients were low (Mantel’s r < 0.21). In addition, AMOVA analyses revealed that differences between landraces collected from five sampled rivers accounted for just 3.05% of observed genetic variance (p < 0.001). Neighbor joining and principal components analyses also revealed little evidence of differentiation between rivers. Finally, in a comparison with a secondary sample, we found that the closest relative of 27 of 28 specimens had a landrace name different from their own, suggesting that traditional nomenclature is a poor indicator of genetic relatedness.

Characterization of the genetic diversity, structure, and admixture of 7 Chilean chicken breeds

The Mapuche fowl is an autochthonous breed raised in Chile and represents an important zoogenetic resource for the local economy. This study aimed at investigating the genetic diversity, relationship and population structure of 96 local Chilean chickens derived from 3 ecotype of Mapuche fowl (Kollonka, Ketro, and Kollonka de aretes), 2 ecotype Chilean (Trintre, Cogote pelado) and 2 breeds (Light Brahma and Barred Plymouth Rock) using 12 microsatellite markers. In total, 113 alleles were detected in all populations, with a mean of 7.6 alleles per population. In all population chicken breeds, the observed and expected heterozygosity ranged from 0.91 to 0.98 and from 0.69 to 0.79. Furthermore, all populations showed significant deviations from Hardy-Weinberg expectations. Across each population, the global heterozygosity deficit (FIT) was -0.174, population differentiation index (FST) was 0.073, and the global inbreeding of individuals within breed (FIS) was -0.267. The phylogenetic relationships of chickens were examined using neighbor-joining trees constructed at the level of population. The highest Nei's standard genetic distance value of 0.559 was observed between Barred Plymouth Rock and Light Brahma, whereas the minimum value (0.099) was found between Kollonka and Trintre. The neighbor-joining tree constructed at population level revealed 2 main clusters, with Light Brahma, Barred Plymouth Rock, Ketro and Kollonka de aretes in 1 cluster, and Kollonka, Trintre and Cogote pelado breeds in the second cluster. Based on the results of the STRUCTURE analysis, the most likely number of clustering of the population evaluated was at K=3, with Light Brahma and Barred Plymouth Rock breeds forming their own distinct clusters, while Kollonka, Ketro, Kollonka de aretes, Trintre and Cogote pelado breeds clustered together. This study represents the first report of genetic diversity in these populations in Chile. These results can be used as baseline genetic information for genetic conservation program, for instance, to control inbreeding and to implement further genetic studies in local Chilean chickens.

Comparative genetic characteristics of microsatellite profile of holstein and purebred kholmogorsky bulls

Relevance. Due to widespread metisation the Kholmogorskaya breed is on the verge of complete extinction, which requires the development of measures aimed at preserving not only the animals themselves, but also their genetic diversity. Microsatellites can be considered the most convenient for analyzing the genetic state of a population, due to the high level of their polymorphism.Methods. The material for genetic examination was cryocon-served sperm of bulls-producers belonging to the RSUP «Komi» for breeding work (Syktyvkar). Samples from 64 pure-bred Kholmogorsky and 36 with different levels of Holstein breeding bulls were selected for analysis. The allelic structure of STR markers was determined in the laboratory of DNA technologies of FGBNU «VNIIplem». The genetic and statistical analysis was carried out according to the methods generally accepted in biology and animal science.Results. Among purebred bulls 9 privat-alleles were identified, and in crossbreed producers — 13. The most polymorphic among Holstein animals were loci TGLA122 (Na = 10) and TGLA227 (Na = 11), in purebred animals — TGLA227 (Na = 9) and TGLA53 (Na = 10). The maximum correspondence between the number of actual and effective alleles was observed at the BM1824 locus, and the minimum at TGLA227. The Shannon index was the highest for the locus TGLA122 (2,046) in crossbreeds and for TGLA53 (2,011) in purebred bulls, and the lowest for BM1818 (1,050 and 1,174). The diversity of the allelofund of the analyzed loci in the metalized animals was slightly higher (by 0.26). The average fixation index in crossbreeds deviated towards a slight deficit of heterozygosity (0.017), and in purebred bulls an excess (-0.025). The greatest genetic relationship between the two samples was observed at the SPS115 locus (0.996), and the smallest at CSSM66 (0.827).

Genetic variation of LEI0258 locus at major histocompatibility complex (MHC) region in Ethiopian indigenous village chicken


 Indigenous chickens are locally adapted to environmental challenges and provide subsistence to millions of farmers in Africa. However, their productivity remains low compared to exotic strains. Efforts are being made to combine the local adaptation of indigenous chicken with productive traits of exotic chicken. Understanding the link between genetic diversity and environmental challenges leads to marker-assisted breed improvement programs for sustainable chicken production at smallholder level. Genetic variation at LEI0258 VNTR locus located within the MHC region has been linked to infectious disease resistance/susceptibility in commercial breeds. The aim of this study was to investigate allelic variability, genetic diversity and genetic relationships of 24 chicken populations in Ethiopia. Here, the diversity at LEI0258 in 236 chickens from 24 Ethiopian indigenous chicken populations using the major Histo-compatibility Complex linked LEI0258 marker is reported. A total of 236 DNA samples were genotyped by capillary electrophoresis from 24 chicken populations. The number of alleles, allele frequency, and heterozygosity levels were used to measure genetic variation at LEI0258 locus in Ethiopian indigenous village chicken. Twenty-nine LEI0258 alleles were observed using capillary electrophoresis that ranged from 185 to 569 bp with no significant difference in allele frequencies between populations. The number of alleles ranged from 179 (Meseret) to 569 (Batambie), with an average of 9.6 alleles per population. Allelic polymorphism was further evaluated through genotyping by Sanger sequencing. Twenty-three DNA samples with different fragment sizes were re-amplified and their alleles sequenced to depict polympormisms based on the combination of two repeat regions at 12 bp and 13 bp, respectively, and flanking regions with SNP and indels. The repeat region at 12 bp appeared 2 to 18 times, whereas the region at 13 bp appeared invariant in all populations. Sequence relationships revealed two distinct groups of alleles. The number of indels and mutations were 33 and 17, respectively. From capillary electrophoresis, the fixation coefficient of the sub-population within the total population (FST), inbreeding/fixation/ coefficient of an individual in a sub population (FIS) and total inbreeding /heterozygosity deficit/ coefficient of an individual within the total population (FIT) in the locus was 0.03, 0.08 and 0.11, respectively. Three percent of the genetic diversity was due to differences among populations, where as 8% and 89% were variations among individuals and variations within individuals, respectively. Despite the overall low genetic differentiation, both fragment and sequencing analysis revealed high allelic and genetic variability across the 24 populations. The high diversity at LEI0258 in Ethiopian indigenous village chicken populations supports the importance of the MHC region in relation to the disease challenges faced by smallholder poultry farmers across Ethiopia. We recommend that breed improvement programs ensure the maintenance of this diversity by selecting breeding stock as diverse as possible at the LEI0258 locus.

Genetic Evaluation in Natural Populations of the Threatened Conifer Amentotaxus argotaenia (Hance) Pilg. (Taxaceae) Using Microsatellites

Amentotaxus argotaenia (Hance) Pilg. is a threatened conifer with a wide distribution range from North to Central Vietnam due to habitat loss and over-exploitation. To provide information for its conservation and sustainable management, in the present study, genetic diversity and population genetic structure for 200 trees from eight populations, representing the natural distribution range of this species were estimated using nuclear microsatellites. The results showed a moderate genetic diversity of A. argotaenia (HO = 0.331, HE = 0.358). Significant heterozygosity deficits were detected in three populations in the Northeast area. Genetic differentiation was low in the same distribution area and high in different areas. However, the gene flow among the studied populations was relatively high (Nm = 1.17). Habitat fragmentation, geographical distance and high mountain range can be the major factors that reduce gene exchange between different areas. Various clustering analyses distinguished three major genetic groups related to the three distribution areas of this species in Vietnam. Based on the study results, we propose that some populations could be prioritized for in situ conservation due to their high genetic diversity with high allelic richness or private alleles, meanwhile other populations should be collected for ex situ conservation as genetic resources in the future.

Genetic Structure of the Endangered Coral Cladocora caespitosa Matches the Main Bioregions of the Mediterranean Sea.

Population connectivity studies are a useful tool for species management and conservation planning, particular of highly threatened or endangered species. Here, we evaluated the genetic structure and connectivity pattern of the endangered coral Cladocora caespitosa across its entire distribution range in the Mediterranean Sea. Additionally, we examined the relative importance of sexual and asexual reproduction in the studied populations and their genetic diversity. A total of 541 individuals from 20 localities were sampled and analysed with 19 polymorphic microsatellite markers. Of the genotyped individuals, 482 (89%) had unique multilocus genotypes. Clonality percentages of the populations varied from 0% (in eight populations) to nearly 69% (in one population from Crete). A heterozygosity deficit and a high degree of inbreeding was the general trend in our data set. Population differentiation in C. caespitosa was characterised by significant pairwise F ST values with lower ones observed at an intraregional scale and higher ones, between populations from different biogeographic regions. Genetic structure analyses showed that the populations are divided according to the three main sub-basins of the Mediterranean Sea: the Western (Balearic, Ligurian and Tyrrhenian seas), the Central (Adriatic and Ionian seas) and the Eastern (Levantine and Aegean seas), coinciding with previously described gene flow barriers. However, the three easternmost populations were also clearly separated from one another, and a substructure was observed for the other studied areas. An isolation-by-distance pattern was found among, but not within, the three main population groups. This substructure is mediated mainly by dispersal along the coastline and some resistance to larval movement through the open sea. Despite the low dispersal ability and high self-recruitment rate of C. caespitosa, casual dispersive events between regions seem to be enough to maintain the species’ considerable genetic diversity. Understanding the population connectivity and structure of this endangered scleractinian coral allows for more informed conservation decision making.

Assessing the Genetic Diversity and Population Structure of a Tunisian Melon (Cucumis melo L.) Collection Using Phenotypic Traits and SSR Molecular Markers

The assessment of genetic diversity and structure of a gene pool is a prerequisite for efficient organization, conservation, and utilization for crop improvement. This study evaluated the genetic diversity and population structure of 24 Tunisian melon accessions, by using 24 phenotypic traits and eight microsatellite (SSR) markers. A considerable phenotypic diversity among accessions was observed for many characters including those related to agronomical performance. All the microsatellites were polymorphic and detected 30 distinct alleles with a moderate (0.43) polymorphic information content. Shannon’s diversity index (0.82) showed a high degree of polymorphism between melon genotypes. The observed heterozygosity (0.10) was less than the expected heterozygosity (0.12), displaying a deficit in heterozygosity because of selection pressure. Molecular clustering and structure analyses based on SSRs separated melon accessions into five groups and showed an intermixed genetic structure between landraces and breeding lines belonging to the different botanical groups. Phenotypic clustering separated the accessions into two main clusters belonging to sweet and non-sweet melon; however, a more precise clustering among inodorus, cantalupensis, and reticulatus subgroups was obtained using combined phenotypic–molecular data. The discordance between phenotypic and molecular data was confirmed by a negative correlation (r = −0.16, p = 0.06) as revealed by the Mantel test. Despite these differences, both markers provided important information about the diversity of the melon germplasm, allowing the correct use of these accessions in future breeding programs. Together they provide a powerful tool for future agricultural and conservation tasks.

A reference-free approach to analyse RADseq data using standard next generation sequencing toolkits.

Genotyping-by-sequencing methods such as RADseq are popular for generating genomic and population-scale data sets from a diverse range of organisms. These often lack a usable reference genome, restricting users to RADseq specific software for processing. However, these come with limitations compared to generic next generation sequencing (NGS) toolkits. Here, we describe and test a simple pipeline for reference-free RADseq data processing that blends de novo elements from STACKS with the full suite of state-of-the art NGS tools. Specifically, we use the de novo RADseq assembly employed by STACKS to create a catalogue of RAD loci that serves as a reference for read mapping, variant calling and site filters. Using RADseq data from 28 zebra sequenced to ~8x depth-of-coverage we evaluate our approach by comparing the site frequency spectra (SFS) to those from alternative pipelines. Most pipelines yielded similar SFS at 8x depth, but only a genotype likelihood based pipeline performed similarly at low sequencing depth (2-4x). We compared the RADseq SFS with medium-depth (~13x) shotgun sequencing of eight overlapping samples, revealing that the RADseq SFS was persistently slightly skewed towards rare and invariant alleles. Using simulations and human data we confirm that this is expected when there is allelic dropout (AD) in the RADseq data. AD in the RADseq data caused a heterozygosity deficit of ~16%, which dropped to ~5% after filtering AD. Hence, AD was the most important source of bias in our RADseq data.

Mediterranean swordfish (Xiphias gladius Linnaeus, 1758) population structure revealed by microsatellite DNA: genetic diversity masked by population mixing in shared areas.

BackgroundThe Mediterranean swordfish stock is overfished and considered not correctly managed. Elucidating the patterns of the Mediterranean swordfish population structure constitutes an essential prerequisite for effective management of this fishery resource. To date, few studies have investigated intra-Mediterranean swordfish population structure, and their conclusions are controversial.MethodsA panel of 20 microsatellites DNA was used to investigate fine-scale population structuring of swordfish from six main fishing areas of the Mediterranean Sea.ResultsThis study provides evidence to reject the hypothesis of a single swordfish population within the Mediterranean Sea. DAPC analysis revealed the presence of three genetic clusters and a high level of admixture within the Mediterranean Sea. Genetic structure was supported by significant FST values while mixing was endorsed by the heterozygosity deficit observed in sampling localities indicative of a possible Wahlund effect, by sampling admixture individuals. Overall, our tests reject the hypothesis of a single swordfish population within the Mediterranean Sea. Homing towards the Mediterranean breeding areas may have generated a weak degree of genetic differentiation between populations even at the intra-basin scale.

Genetic variability following selection for scrapie resistance in six autochthonous sheep breeds in the province of Bolzano (northern Italy).

Scrapie is an ovine transmissible spongiform encephalopathy, and its susceptibility is associated with polymorphisms in the prion protein gene (PRNP). Genetic selection is currently the most effective mean for eradication of the susceptible VRQ allele in favour of resistant ARR allele. Maintenance of genetic diversity should be one of the major objectives in breeding programmes, especially in endangered breeds, and genetic information are an excellent alternative to pedigree data where these information are missing. The aim of our study was to determine changes of genetic variability in six native sheep breeds from autonomous province of Bolzano, northern Italy, following simulation of scrapie selection scenarios. A total of 684 rams were investigated for PRNP polymorphisms and for 10 microsatellite loci to estimate genetic variability. Across all loci, a total of 163 alleles were detected with a mean of 10.4 alleles per locus. Average observed (Ho) and unbiased expected (uHe) heterozygosity overall loci were 0.74 and 0.78, respectively, showing a statistically significant deviation from Hardy-Weinberg equilibrium (HWE) in all breeds. This heterozygosity deficit was confirmed by a positive fixation index (Fis), determining a moderate inbreeding in each breed. Simulating a soft selection, where only rams having at least a VRQ allele should be excluded from reproduction, Ho, uHe and Fis values remained almost unchanged, indicating that genetic variability should not be affected by the removal of these individuals. With a mild selection scenario, considering only rams with at least one ARR allele, we observed a decrease in the mean alleles per breed (8.9) and the maintenance of heterozygosity deficiency, except for two breeds, where it was any longer significant. These results showed that selection strategies allowing use of heterozygous as well homozygous ARR rams might be the right compromise to improve resistance to scrapie and to do not dramatically affect genetic variability of these breeds.

Short Tandem Repeat (STR) based assessment of genetic diversity of Alambadi - A draught cattle breed of Tamil Nadu

Alambadi is one of the five indigenous draught type cattle breeds of Tamil Nadu. The present study was undertaken to establish baseline genetic diversity information and evaluate its genetic relationship with Bargur cattle. The results suggested moderate levels of allelic diversity and observed heterozygosity with an overall mean of 6.52 and 0.666 respectively. Estimates of FIS showed significant heterozygosity deficit (0.056) indicating relatively higher levels of inbreeding in Alambadi cattle. The test for Hardy-Weinberg equilibrium revealed 11.1% (3 out of 27) of the investigated loci showing significant deviations due to heterozygosity deficit. Estimation of global F statistics revealed low genetic differentiation between Alambadi and Bargur cattle. The global FST indicated only 3% of the total variation being explained by between breed differences, while the remaining 97% was explained by within breed variability. Principal components analysis revealed separate clustering of Alambadi and Bargur cattle, although admixture was observed among few animals from both the breeds. The test for mutation drift equilibrium revealed no evidences for the occurrence of genetic bottleneck in Alambadi and Bargur cattle in the recent past. Considering the rapid decline in the population of Alambadi cattle, the results of the present study is expected to help planning the strategy for genetic conservation and breed improvement.

Genetic characterization of promising high-yielding cashew (Anacardium occidentale L.) cultivars from Côte d'Ivoire

Description of the subject. Cashew was introduced to Côte d'Ivoire in 1951 to control erosion and reforest cutover lands. From 1972 to 1980, natural forest plantations were converted to fruit orchards and were supplemented by the ‘Jumbo’ cashew variety imported from Brazil. Germplasm expeditions conducted in 2010 and 2014–2015 identified 209 high-yielding cultivars in the major cashew growing areas of Côte d’Ivoire. Although the morphological characteristics of these cultivars have been assessed, little is known about the genetic diversity and genetic structure of the germplasm collection. Objectives. The objective of the study was to evaluate the genetic diversity of high-yielding cashew cultivars for better use in breeding programs. Method. We performed DNA isolation using Qiagen DNeasy Plant Mini Kits and PCR analysis with 18 SSR markers. Results. We identified the first two introduced populations of cashew in Côte d’Ivoire. The average allelic richness is 3.56 (± 1.45) alleles per locus, the fixation index (FIS) indicates an overall heterozygosity deficit of 0.332 (± 0.076), and the average population differentiation (FST) is 0.014 (± 0.004). Much of the total genetic variability occurs at the intra-population level (98.6%), compared to only 1.4% variability attributable to differences between populations. Average value of gene flow is 22.528. Conclusions. Gene flow within cashew populations maintains high intra-population genetic diversity. This flow rate reflects a long-term exploitable genetic variability for use in selection and conservation.

Genetic structure of Anopheles gambiae s.s populations following the use of insecticides on several consecutive years in southern Benin

BackgroundSeveral studies have reported the strong resistance of Anopheles gambiae s.l. complex species to pyrethroids. The voltage-dependent sodium channel (Vgsc) gene is the main target of pyrethroids and DDT. In Benin, the frequency of the resistant allele (L1014F) of this gene varies along the north-south transect. Monitoring the evolution of resistance is necessary to better appreciate the genetic structure of vector populations in localities subject to the intensive use of chemicals associated with other control initiatives. The purpose of this study was to map the distribution of pyrethroid insecticide resistance alleles of the Kdr gene in malaria vectors in different regions and ecological facies in order to identify the evolutionary forces that might be the basis of anopheline population dynamics.MethodsThe characterization of Anopheles gambiae s.l. populations and resistance mechanisms were performed using adult mosquitoes obtained from larvae collected in the four agroecological zones in southern Benin. Genomic DNA extraction was performed on whole mosquitoes.The extracted genomic DNA from them were used for the molecular identification of species in Anopheles gambiae s.l. complex and the identification of genotypes related to pyrethroid resistance as the Kdr gene amino acid position 1014 in sodium channel. Molecular speciation and genotyping of Kdr resistant alleles (1014) were done using PCR.Genepop software version 4.2 was used to calculate allelic and genotypic frequencies in each agroecological zone. The p value of the allelic frequency was determined using the binomial test function in R version 3.3.3. The Hardy-Weinberg equilibrium was checked for each population with Genetics software version 1.3.8.1. The observed heterozygosity and the expected heterozygosity as well as the fixation index and genetic differentiation index within and between populations were calculated using Genepop software version 4.2.ResultsDuring the study period, Anopheles coluzzii was the major species in all agroecological zones while Anopheles gambiae was scarcely represented. Regardless of the species, resistant homozygote individuals (L1014F/L1014F) were dominant in all agroecological zones, showing a strong selection of the resistant allele (L1014F). All populations showed a deficit of heterozygosity. No genetic differentiation was observed between the different populations of the two species. For Anopheles coluzzii, there was a small differentiation among the populations of the central cotton and bar-lands zones. The genetic differentiation was modest among the population of the fisheries zone (Fst = 0.1295). The genetic differentiation was very high in the population of Anopheles gambiae of the bar-lands zone (Fst = 0.2408).ConclusionThis study revealed that the use of insecticides in Benin for years has altered the genetic structure of Anopheles gambiae s.s. populations in all agroecological zones of southern Benin. It would be desirable to orientate vector control efforts towards the use of insecticides other than pyrethroids and DDT or combinations of insecticides with different modes of action.

Microsatellite marker-based estimation of the genetic diversity of cattle in Chongqing

Cattle are the main source of meat in Chongqing. This study investigated the genetic diversity of cattle native to Chongqing and 4 introduced breeds. A total of 96 individuals from 5 breeds were genotyped using six microsatellite markers. Five markers were highly polymorphic within the breed populations, and one marker had moderate levels of polymorphism. Heterozygosity ranged from 0.5379±0.0434 in Simmental to 0.6667±0.0559 in Charolais. The heterozygosity deficit was significant in all populations analyzed compared with the expected level of heterozygosity. In addition, two microsatellite markers (TGLA53 and OarFCB20) deviated from Hardy-Weinberg equilibrium across populations (except in cattle native to Chongqing). The mean number of alleles ranged from 6.00±2.37 in Angus to 7.17±2.14 in Droughtmaster across six markers. The coefficient of inbreeding ranged from 0.0017 in Simmental and Droughtmaster to 0.0367 in Angus. Pairwise difference analyses revealed that Simmental and Droughtmaster were the most differentiated (FST= 0.06861) from each other, whereas cattle native to Chongqing and Charolais were the least differentiated (FST= 0.00557). In summary, this study showed that cattle native to Chongqing and 4 introduced breeds were genetically well protected in Chongqing, and information from this study would be helpful for guiding hybridization and genetic improvements in the future.

SSR-Marker assisted evaluation of Genetic Diversity in Mungbean ( Vigna radiata (L.) Wilcezk) genotypes

ABSTRACT Mungbean (Vigna radiata (L.) Wilczek) also known as green gram is an important source of protein in the category of food legumes. In the present study, SSR marker is used to analyze the genetic diversity amongst 23 genotypes of mungbean. Out of a total of 10 primers used for SSR analysis revealed generation of 15 alleles. The number of alleles per locus ranged from one (CEDG006, CEDG010, CEDG050, CEDG088, CEDG092 and CEDG232) to three (CEDG 214), with an average of 1.5 allele per primer. The index for expected heterozygosity was 0.29 ranging from 0.15 to 0.49 revealed a deficit in heterozygosity. The size of amplification products varied in case of each primer and the range was found to be 100 bp to 190 bp. 13 out of 15 alleles were found polymorphic. The average PIC value of SSR marker was found to be 0.205. The value of Jaccard’s similarity coefficient had ranged from 0.28-1.00 with an average value of 0.64. The dendrogram constructed on SSR molecular marker data through UPGMA method and PCA using average linkage, had enabled grouping of the genotypes into three main clusters. Clustering pattern based on SSR marker data clearly indicated the narrow genetic base of mungbean genotypes that emphasizes the need to explore and exploit more number of germplasm from additional source to study genetic variation in mungbean for genetic improvement. The results indicated the marked usefulness of SSR in the assessment of genetic diversity in mungbean crop.

Extensive gene flow of white-backed planthopper in the Greater Mekong Subregion as revealed by microsatellite markers

The white-backed planthopper (WBPH), Sogatella furcifera (Horváth), is a destructive pest of rice in the Greater Mekong Subregion (GMS) countries including Cambodia, Laos, Myanmar, Thailand, Vietnam, and China’s Yunnan Province. Our previous study not only confirmed the immigration sources of the WBPH in China’s Yunnan Province were from Myanmar, Vietnam, and Laos, but also indicated that Cambodia was likely an additional migration source. To further clarify the migration sources and patterns of the WBPH in the GMS, we investigated the genetic structure of 42 WBPH populations using microsatellite loci markers. The analysis of genetic diversity, heterozygosity deficit, and heterozygosity excess based on the nuclear markers suggest that there is extensive gene flow between the 42 sampled populations from the GMS. The genetic structure confirmed the immigration sources of WBPH as revealed by mitochondrial markers and trajectory analyses methods in previous studies. These findings will aid in the sustainable regional management of this insect pest in the GMS.