Duplicate Genotypes Research Articles

Trait-customized sampling of core collections from a winter wheat genebank collection supports association studies.

Subsampling a reduced number of accessions from ex situ genebank collections, known as core collections, is a widely applied method for the investigation of stored genetic diversity and for an exploitation by breeding and research. Optimizing core collections for genome-wide association studies could potentially maximize opportunities to discover relevant and rare variation. In the present study, eight strategies to sample core collections were implemented separately for two traits, namely susceptibility to yellow rust and stem lodging, on about 6,300 accessions of winter wheat (Triticum aestivum L.). Each strategy maximized different parameters or emphasized another aspect of the collection; the strategies relied on genomic data, phenotypic data or a combination thereof. The resulting trait-customized core collections of eight different sizes, covering the range between 100 and 800 accession samples, were analyzed based on characteristics such as population stratification, number of duplicate genotypes and genetic diversity. Furthermore, the statistical power for an association study was investigated as a key criterion for comparisons. While sampling extreme phenotypes boosts the power especially for smaller core collections of up to 500 accession samples, maximization of genetic diversity within the core collection minimizes population stratification and avoids the accumulation of less informative duplicate genotypes when increasing the size of a core collection. Advantages and limitations of different strategies to create trait-customized core collections are discussed for different scenarios of the availability of resources and data.

Exploring morphological variation and stability in hot pepper (Capsicum annuum) germplasm collection from the northern region of Ghana

Understanding genetic variability in pepper (Capsicum annuum L.) will contribute to effective breeding efforts, especially in northern Ghana, where pepper contributes significantly to the smallholder farmer's income. This study evaluated 13 morphological traits including those related to vegetative, inflorescence, and fruit-related within a collection of 40 pepper genotypes from five different locations in the northern region of Ghana. Significant variations (p < 0.05) were detected among the pepper genotypes for all measured traits. A strong positive correlation was detected between days to 50 % flowering and days to 50 % fruiting for both the rainfed (r = 0.87) and irrigated (r = 0.73) conditions. High performance of the genotypes at the vegetative and inflorescence stages was observed in the dry season, with low fruiting performance (number of fruits per plant, fresh weight, and dry weight). Multivariate analysis revealed that 60.54 % and 54.63 % variations were explained by the first three principal components, respectively. Three main clusters were identified, with linear relationships and no distinct separation pattern based on location, thus providing an opportunity to remove duplicate genotypes in the studied region. The results indicated that the selection of genotypes with better agronomic traits could be achieved from this pepper gene pool. The present findings may pave the way for better utilization and production of pepper, leading to improved adaptation in the region.

Copy number deletion of PLA2G4A affects the susceptibility and clinical phenotypes of schizophrenia

Phospholipase A2(PLA2) superfamily is recognized as being involved in the pathogenesis of schizophrenia by affecting lipid homeostasis in cell membranes. We hypothesized that PLA2 gene copy number variation (CNV) may affect PLA2 enzyme expression and be associated with schizophrenia risk. This study indicated that in the discovery stage, an increased copy number of PLA2G6 and the deletion of PLA2G3, PLA2G4A, PLA2G4F and PLA2G12F was associated with increased risk of schizophrenia. CNV segments involving six PLA2 genes were detected in publicly available datasets, including two deletion segments specific to the PLA2G4A gene. The relationship between the deletion of PLA2G4A and susceptibility to schizophrenia was then reaffirmed in the validation group of 806 individuals. There was a significant correlation between PLA2G4A deletion and the symptoms of poverty of thought in male patients and erotomanic delusion in females. Furthermore, ELISA results demonstrate a significant decrease in peripheral blood cytosolic PLA2(cPLA2) levels in patients with the PLA2G4A deletion genotype compared to those with normal and copy number duplicate genotypes. These data suggest that the functional copy number deletion in the PLA2G4A gene is associated with the risk of schizophrenia and clinical phenotypes by reducing the expression of cPLA2, which may be an indicator of susceptibility to schizophrenia.

Genetic basis of ear length in sheep breeds sampled across the region from the Middle East to the Alps.

Ear length in sheep (Ovis aries) shows a wide range of natural variation, from the absence of an outer ear structure (anotia), to small outer ears (microtia), to regular ear length. Up until now, the underlying genetics of this phenotype has been studied in four sheep breeds from China, Jordan and Italy. These studies revealed a broad range of genes significantly associated with ear length, potentially indicating genetic heterogeneity across breeds or geographic regions. In the current study, we performed genome-wide SNP genotyping and haplotype-based mapping, in a population of 340 individuals, to identify loci influencing ear length variation in additional sheep breeds from Slovenia, Croatia, Cyprus and Greece. Additionally, two previously described candidate variants were also genotyped in our mapping population. The mapping model without candidate variant genotypes revealed only one genome-wide significant signal, which was located next to HMX1 on OAR6. This region was previously described as being associated with ear length variation in the Altay and Awassi sheep breeds. The mapping model including the candidate duplication genotype near HMX1 as a fixed effect explained the phenotypic variance on OAR6 and revealed an additional genome-wide significant locus on OAR13 associated with ear length. Our results, combined with published evidence, suggest that a duplication in the evolutionarily conserved region near HMX1 is the major regulator of ear length in sheep breeds descended from a larger region from Central Asia, to the Middle East, Cyprus, Greece and to the Alps. This distribution suggests an ancient origin of the derived allele.

Mutations in ompK36 differentially impact in vitro synergy of meropenem/vaborbactam and ceftazidime/avibactam in combination with other antibiotics against KPC-producing Klebsiella pneumoniae.

Ceftazidime/avibactam and meropenem/vaborbactam are preferred agents for Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae (KPC-Kp) infections and are often used in combination with other agents. We aimed to characterize the synergy of combinations against KPC-Kp with varying ompK36 genotypes. KPC-Kp that harboured ompK36 WT, IS5 or glycine-aspartic acid duplication (GD) genotypes were selected. MICs were determined in triplicate. Synergy was assessed by time-kill assays for ceftazidime/avibactam and meropenem/vaborbactam in combination with colistin, gentamicin, tigecycline, meropenem or fosfomycin against 1 × 108 cfu/mL KPC-Kp. KPC-Kp harboured ompK36 WT (n = 5), IS5 (n = 5) or GD (n = 5); 11 were KPC-2 and 4 were KPC-3. All were susceptible to ceftazidime/avibactam and meropenem/vaborbactam. In time-kill analysis, ceftazidime/avibactam and meropenem/vaborbactam 1 × MIC exhibited mean 24 h log-kills of -2.01 and -0.84, respectively. Ceftazidime/avibactam was synergistic in combination with colistin independent of ompK36 genotype. Ceftazidime/avibactam combinations impacted by porin mutations (compared to WT) were meropenem (-5.18 versus -6.62 mean log-kill, P < 0.001) and fosfomycin (-3.98 versus -6.58, P = 0.058). Mean log-kills with meropenem/vaborbactam were greatest in combination with gentamicin (-5.36). In the presence of porin mutations, meropenem/vaborbactam killing activity was potentiated by the addition of colistin (-6.65 versus -0.70, P = 0.03) and fosfomycin (-3.12 versus 1.54, P = 0.003). Our results shed new light on the synergy of ceftazidime/avibactam and meropenem/vaborbactam combinations against KPC-Kp with or without porin mutations. Killing activity of ceftazidime/avibactam with other cell wall active agents was decreased against isolates with porin mutations. On the other hand, some meropenem/vaborbactam combinations demonstrated enhanced killing in the presence of porin mutations.

Identification of Duplication Genotypes of the Feathering Rate Gene in Chicken by a Multiplex PCR Following Electrophoresis and/or Sanger Sequencing

Sex-linked phenotypes of late feathering (LF) and early feathering (EF) are controlled by a pair of alleles K and k+. Autosexing based on the feathering rate is widely used in poultry production. It is reported that a tandem duplication of 176,324 base pairs linked to the K locus is responsible for LF expression and could be used as a molecular marker to detect LF chicken. So far, there is no genotyping method that can accurately and stably identify the LF homozygote and heterozygote in all chicken breeds. In the present study, a multiplex PCR test was developed to identify EF, LF homozygote, and heterozygote according to electrophoretic bands and the relative height of the peaks by Sanger sequencing. We tested 413 chickens of six native Chinese breeds with this method. The identification was consistent with the sex and phenotype records of the chickens. Band density analysis was performed, and the results supported our genotyping using the new assay. In order to further verify the accuracy of this test in distinguishing homozygote and heterozygote males, 152 LF males were mated with EF females, and the results of the offspring's phenotypes were consistent with our expectations. Our results support tandem duplication as molecular markers of LF, and this new test is applicable to all LF chickens associated with tandem duplication.

Whole-Genome Duplication and Host Genotype Affect Rhizosphere Microbial Communities.

ABSTRACTThe composition of microbial communities found in association with plants is influenced by host phenotype and genotype. However, the ways in which specific genetic architectures of host plants shape microbiomes are unknown. Genome duplication events are common in the evolutionary history of plants and influence many important plant traits, and thus, they may affect associated microbial communities. Using experimentally induced whole-genome duplication (WGD), we tested the effect of WGD on rhizosphere bacterial communities in Arabidopsis thaliana. We performed 16S rRNA amplicon sequencing to characterize differences between microbiomes associated with specific host genetic backgrounds (Columbia versus Landsberg) and ploidy levels (diploid versus tetraploid). We modeled relative abundances of bacterial taxa using a hierarchical Bayesian approach. We found that host genetic background and ploidy level affected rhizosphere community composition. We then tested to what extent microbiomes derived from a specific genetic background or ploidy level affected plant performance by inoculating sterile seedlings with microbial communities harvested from a prior generation. We found a negative effect of the tetraploid Columbia microbiome on growth of all four plant genetic backgrounds. These findings suggest an interplay between host genetic background and ploidy level and bacterial community assembly with potential ramifications for host fitness. Given the prevalence of ploidy-level variation in both wild and managed plant populations, the effects on microbiomes of this aspect of host genetic architecture could be a widespread driver of differences in plant microbiomes.IMPORTANCE Plants influence the composition of their associated microbial communities, yet the underlying host-associated genetic determinants are typically unknown. Genome duplication events are common in the evolutionary history of plants and affect many plant traits. Using Arabidopsis thaliana, we characterized how whole-genome duplication affected the composition of rhizosphere bacterial communities and how bacterial communities associated with two host plant genetic backgrounds and ploidy levels affected subsequent plant growth. We observed an interaction between ploidy level and genetic background that affected both bacterial community composition and function. This research reveals how genome duplication, a widespread genetic feature of both wild and crop plant species, influences bacterial assemblages and affects plant growth.

Genomic-based epidemiology reveals independent origins and gene flow of glyphosate resistance in Bassia scoparia populations across North America.

Genomic‐based epidemiology can provide insight into the origins and spread of herbicide resistance mechanisms in weeds. We used kochia (Bassia scoparia) populations resistant to the herbicide glyphosate from across western North America to test the alternative hypotheses that (i) a single EPSPS gene duplication event occurred initially in the Central Great Plains and then subsequently spread to all other geographical areas now exhibiting glyphosate‐resistant kochia populations or that (ii) gene duplication occurred multiple times in independent events in a case of parallel evolution. We used qPCR markers previously developed for measuring the structure of the EPSPS tandem duplication to investigate whether all glyphosate‐resistant individuals had the same EPSPS repeat structure. We also investigated population structure using simple sequence repeat markers to determine the relatedness of kochia populations from across the Central Great Plains, Northern Plains and the Pacific Northwest. We found that the original EPSPS duplication genotype was predominant in the Central Great Plains where glyphosate resistance was first reported. We identified two additional EPSPS duplication genotypes, one having geographical associations with the Northern Plains and the other with the Pacific Northwest. The EPSPS duplication genotype from the Pacific Northwest seems likely to represent a second, independent evolutionary origin of a resistance allele. We found evidence of gene flow across populations and a general lack of population structure. The results support at least two independent evolutionary origins of glyphosate resistance in kochia, followed by substantial and mostly geographically localized gene flow to spread the resistance alleles into diverse genetic backgrounds.

Effects Of Molecular Markers Consequences On Genotyping Errors

Genotype error can greatly reduce the power of a genetic study. For family data, genotype error can be assessed by examining marker data for non-Mendelian inconsistencies, closely linked markers for double recombination events, and consistency of duplicate genotypes. Genetic markers are widely used to determine the parentage of individuals in studies of mating systems, reproductive success, dispersals, quantitative genetic parameters and in the management of conservation populations. These markers are, however, imperfect for parentage analyses because of the presence of genotyping errors and undetectable alleles, which may cause incompatible genotypes (mismatches) between parents and offspring and thus result in false exclusions of true parentage. Highly polymorphic markers widely used in parentage analyses, such as microsatellites, are especially prone to genotyping errors. Molecular markers based on a hybridization reaction or PCR stage that detect DNA polymorphism are currently used in various fields of biology, including the study and preservation of genetic diversity, identification of individuals, phylogenetic, mapping of useful traits of quality and resistance to stress factors. , in the breeding process, biotechnology, etc. Before starting the experiment, researchers must determine what type of markers to use based on the following criteria: the variability and number of required markers, the need for their codominance, the corresponding requirements for the extracted DNA; practical - efficiency, reproducibility of analysis, the necessary appropriate technical support and cost. For a correct interpretation of the results of genotyping, one should take into account the fact that the use of any type of molecular markers is associated with a number of genotyping errors, the main ones being the loss of larger alleles, “zero” alleles, “stutter” alleles due to the peculiarities of Tag polymerase, and non-homology of amplified sequences of the same size (homoplasia). Researchers formulate defining conditions to reduce genotyping errors and reduce their impact on the final analysis. These include the quality and quantity of analyzed DNA, the level of technical capabilities and professionalism of the staff, since the human factor is defined as one of the main reasons for incorrect results; conducting pilot experiments for a comparative assessment of the theoretical and real error rate. The minimization of errors is achieved by assessing the capabilities of a particular type and screening markers; optimization of experimental methods, proper use of controls, replicates, and development of statistical approaches to identify errors. The trade-off between culling error-generating loci and increasing the potential of the retained loci to amplify the genetic signal can be different in different studies, but the main thing is that this signal is not lost for the sake of an “acceptable” level of error and the researchers develop empirical approaches to achieve the desired compromise.so that this signal is not lost for the sake of an acceptable level of error and researchers develop empirical approaches to achieve the desired compromise.so that this signal is not lost for the sake of an acceptable level of error and researchers develop empirical approaches to achieve the desired compromise.

Concordance rate in cattle and sheep between genotypes differing in Illumina GenCall quality score.

Proper quality control of data prior to downstream analyses is fundamental to ensure integrity of results; quality control of genomic data is no exception. While many metrics of quality control of genomic data exist, the objective of the present study was to quantify the genotype and allele concordance rate between called single nucleotide polymorphism (SNP) genotypes differing in GenCall (GC) score; the GC score is a confidence measure assigned to each Illumina genotype call. This objective was achieved using Illumina beadchip genotype data from 771 cattle (12428767 genotypes in total post-editing) and 80 sheep (1557360 SNPs genotypes in total post-editing) each genotyped in duplicate. The called genotype with the lowest associated GC score was compared to the genotype called for the same SNP in the same duplicated animal sample but with a GC score of >0.90 (assumed to represent the true genotype). The mean genotype concordance rate for a GC score of <0.300, 0.300-0.549, and ≥0.550 in the cattle (sheep in parenthesis) was 0.9467 (0.9864), 0.9707 (0.9953), and 0.9994 (0.99997) respectively; the respective allele concordance rate was 0.9730 (0.9930), 0.9849 (0.9976), and 0.9997 (0.99998). Hence, concordance eroded as the GC score of the called genotype reduced, albeit the impact was not dramatic and was not very noticeable until a GC score of <0.55. Moreover, the impact was greater and more consistent in the cattle population than in the sheep population. Furthermore, an impact of GC score on genotype concordance rate existed even for the same SNP GenTrain value; the GenTrain value is a statistical score that depicts the shape of the genotype clusters and the relative distance between the called genotype clusters.

The genomic landscape of metastatic castration-resistant prostate cancers reveals multiple distinct genotypes with potential clinical impact

Metastatic castration-resistant prostate cancer (mCRPC) has a highly complex genomic landscape. With the recent development of novel treatments, accurate stratification strategies are needed. Here we present the whole-genome sequencing (WGS) analysis of fresh-frozen metastatic biopsies from 197 mCRPC patients. Using unsupervised clustering based on genomic features, we define eight distinct genomic clusters. We observe potentially clinically relevant genotypes, including microsatellite instability (MSI), homologous recombination deficiency (HRD) enriched with genomic deletions and BRCA2 aberrations, a tandem duplication genotype associated with CDK12−/− and a chromothripsis-enriched subgroup. Our data suggests that stratification on WGS characteristics may improve identification of MSI, CDK12−/− and HRD patients. From WGS and ChIP-seq data, we show the potential relevance of recurrent alterations in non-coding regions identified with WGS and highlight the central role of AR signaling in tumor progression. These data underline the potential value of using WGS to accurately stratify mCRPC patients into clinically actionable subgroups.

Exploring the genetic diversity within traditional Philippine pigmented Rice

BackgroundThe wild ancestors of domesticated rice had red seed, white rice being the result of a mutation in the rice domestication gene Rc. Many pigmented rice landraces are still grown by ethnic communities for their nutritional and cultural value. This study assesses the genetic diversity in a collection of pigmented rice accessions from the Philippines.ResultsWe undertook an analysis of the genetic and colour variation in a collection of 696 pigmented rice accessions held at PhilRice in the Philippines. The collection was reduced to 589 genotypes after removal of accessions with limited passport data or with low SNP marker call rates. Removal of duplicate genotypes resulted in a final, core collection of 307 accessions, representing all administrative districts of the Philippines, and composed predominately of japonica and indica sub-species. No genetic structure was observed in the core collection based on geographic origin. A pairwise comparison of accessions by region indicating that both local and long-distance exchange of rice accessions had occurred. The majority of the genetic variation was within regions (82.38%), rather than between regions (10.23%), with the remaining variation being within rice accession variance (7.39%). The most genetically diverse rice accessions originated from the Cordillera Administrative Region (CAR) in the far north of the Philippines, and in the regions of Davao and Caraga in the southeast. A comparison with pigmented rice accessions from the neighbouring countries Taiwan, Laos, China and India revealed a close relationship between accessions from Taiwan, supporting the hypothesis of southward diffusion of Austronesians from Taiwan to the Philippine. The 14-bp deletion within the gene Rc, known to result in loss of red pigmentation, was found in 30 accessions that still had coloured pericarps. Multi-spectral phenotyping was used to measure seed geometric and colour-appearance traits in 197 accessions from the core collection. The purple and variable purple rice accessions had the lowest values for the seed colour parameters - lightness (L*), intensity, saturation, a* (green – red; redness) and b* (blue – yellow; yellowness).ConclusionThese pigmented rice accessions represent a diverse genetic resource of value for further study and nutritional improvement of commercial rice varieties.

No association of TP53 codon 72 and intron 3 16-bp duplication polymorphisms with breast cancer risk in Chinese Han women: new evidence from a population-based case\u2013control investigation

BackgroundMany studies have demonstrated that the genetic variants of tumor suppressor gene TP53 contribute to the prediction of breast cancer risk. However, most of them focused on Europeans and Americans; the investigations about Asians, especially Chinese women, are scarce. Thus, the aim of this study was to explore the influence of TP53 codon 72 and intron 3 16-bp duplication polymorphisms on the breast cancer risk in Chinese women, especially those from eastern China.MethodsBlood samples collected from 254 breast cancer patients and 252 healthy female individuals were investigated. Genotypes of the two polymorphisms were determined by direct sequencing and conventional PCR, respectively.ResultsHeterozygous Arg/Pro and homozygous Del/Del were the most frequent genotypes of the two polymorphisms, respectively. Heterozygous Arg/Pro had a higher prevalence in breast cancer cases (Padj = 0.10; ORadj = 1.43, 95% CI 0.93–2.18), and no homozygous 16-bp duplication (Ins/Ins) genotype was found in the whole 506 clinical samples. For the distributions of allele and haplotype frequencies, no statistically significant difference was observed between the two groups when multiple (additive, dominant and recessive) genetic models were utilized in the analysis (Padj > 0.05).ConclusionThe results suggested that the two TP53 polymorphisms did not affect breast cancer risk in Chinese Han women, but the heterozygous Arg/Pro may exist as the possible risk genotype of the codon 72 polymorphism in contrast to the homozygous Arg/Arg and Pro/Pro.

Recurrent reciprocal copy number variants: Roles and rules in neurodevelopmental disorders.

Deletions and duplications, called reciprocal CNVs when they occur at the same locus, are implicated in neurodevelopmental phenotypes ranging from morphological to behavioral. In this article, we propose three models of how differences in gene expression in deletion and duplication genotypes may result in deleterious phenotypes. To explore these models, we use examples of the similarities and differences in clinical phenotypes of five reciprocal CNVs known to cause neurodevelopmental disorders: 1q21.1, 7q11.23, 15q13.3, 16p11.2, and 22q11.2. These models and examples may inform some insights into better understanding of gene-phenotype relationships. © 2018 Wiley Periodicals, Inc. Develop Neurobiol 78: 519-530, 2018.

Estimating genotyping errors from genotype and reconstructed pedigree data

Abstract Genotyping errors are rules rather than exceptions in reality, and are found in virtually all but very small datasets. These errors, even when occurring at an extremely low rate, can derail many genetic analyses such as parentage/sibship assignments and linkage/association studies. Nonetheless, few robust and accurate methods are available for estimating the rate of occurrence of genotyping errors and for identifying individual erroneous genotypes at a locus. Methods based on duplicate genotyping are expensive, and estimate genotype inconsistency rather than error rate at a locus. Methods based on Hardy–Weinberg equilibrium tests have low robustness and low power, and apply only to those particular errors that cause excessive homozygosity. Methods based on pedigrees are powerful, robust and accurate. However, they rely on known and complete pedigrees that are unfortunately rarely available from natural populations in the wild. I proposed a maximum likelihood method to reconstruct pedigrees from genotype data with errors occurring at a roughly estimated (presumed) rate. In this paper, I describe how to use the method and inferred pedigree in estimating allelic dropout (or null allele) rate and false allele rate jointly at each marker locus, in identifying the erroneous genotypes, and in inferring the most likely genotypes at each locus of each individual. I examine the power, accuracy and robustness of the method by extensive simulations, and demonstrate the usefulness of the method by analysing three empirical datasets. It is concluded that, both pedigrees and the rates of genotyping errors at each locus can be reliably estimated from the same genotype data by the same likelihood method, when marker information is sufficient and some sampled individuals are first‐degree relatives. The erroneous genotypes are however inferred conservatively, and are reliably detected only when they occur in large families and/or at highly polymorphic loci. Estimation of genotyping error rates per locus and identification of erroneous genotypes of each individual at each locus should be routinely conducted to assess and improve data quality, to highlight markers for optimization of genotyping protocols or for replacement, and to enable the integration of genotyping errors in a robust statistical analysis.

Case Study: Polymelia in a Holstein calf

Polymelia, the manifestation of extra limbs or parts of limbs, occurs when there is a developmental duplication in the novel NHL repeat domain containing protein (NHLRC2) gene in Angus cattle. In Holstein cattle, little is known about the etiology of polymelia. To determine the genetic etiology of polymelia in a Holstein calf, genotyping and sequencing of the Angus developmental duplication locus, karyotyping, and a genome-wide association analysis were performed. The genome-wide association analysis compared the polymelia calf (case) to 2,650 control (normal) Holstein calves using EMMAX-GRM (Efficient Mixed-Model Association eXpedited-Genomic Relationship Matrix) software. In addition, homozygous loci within genes in the case that were never found in a control were also evaluated as putative loci. The polymelia calf had a normal Angus developmental duplication genotype that was confirmed by sequencing. Karyotyping revealed no evidence of chromosomal breakage or gross chromosomal abnormalities in the polymelia calf. The additive genome-wide association analysis identified loci associated with polymelia on BTA13 (P < 1 × 10−281) and BTA10 (P < 2 × 10−110). Seventy-nine candidate genes were identified that contained homozygous genotypes in the case that were never identified in 2,650 controls. Candidate genes include MSH homeobox 2 (MSX2) on BTA20, which has been associated with limb development in mice, and GINS complex subunit 1 (GINS1) on BTA13, which is involved in early embryogenesis in mice. In summary, these results suggest that the etiology of polymelia differs by cattle breed and is the result of genetic variants at more than one locus.

Validating the use of non-invasively sourced DNA for population genetic studies using pedigree data

Abstract. Non-invasive genetic sampling has provided valuable ecological data for many species – data which may have been unobtainable using invasive sampling methods. However, DNA obtained non-invasively may be prone to increased levels of amplification failure and genotyping error. Utilizing genotype data from 32 pedigreed koalas, this study aimed to validate the reliability of final consensus genotypes obtained using DNA isolated from koala scats. Pedigree analysis, duplicate genotyping, analysis of mismatched loci and tests for null alleles were used to look for evidence of errors. All genetically confirmed parent–offspring relationships were found to follow Mendelian rules of inheritance. Duplicate genotypes matched in all cases and there was no evidence of null alleles. Related individuals always had different 12-marker genotypes having a minimum of three unique loci (in one full sibling pair), a mode of seven unique loci and a maximum of 11 unique loci. This study demonstrates the capacity of DNA recovered from koala scats to provide reliable genotypes that can unequivocally discriminate individuals and infer parentage, provided data are missing from no more than two loci. Validating data obtained using non-invasive sampling is an important step, allowing potential problems to be identified at an early stage.

About Ganoderma boninense in oil palm plantations of Sumatra and peninsular Malaysia: Ancient population expansion, extensive gene flow and large scale dispersion ability

Wood rot fungi form one of the main classes of phytopathogenic fungus. The group includes many species, but has remained poorly studied. Many species belonging to the Ganoderma genus are well known for causing decay in a wide range of tree species around the world. Ganoderma boninense, causal agent of oil palm basal stem rot, is responsible for considerable yield losses in Southeast Asian oil palm plantations. In a large-scale sampling operation, 357 sporophores were collected from oil palm plantations spread over peninsular Malaysia and Sumatra and genotyped using 11 SSR markers. The genotyping of these samples made it possible to investigate the population structure and demographic history of G. boninense across the oldest known area of interaction between oil palm and G. boninense. Results show that G. boninense possesses a high degree of genetic diversity and no detectable genetic structure at the scale of Sumatra and peninsular Malaysia. The fact that few duplicate genotypes were found in several studies including this one supports the hypothesis of spore dispersal in the spread of G. boninense. Meanwhile, spatial autocorrelation analysis shows that G. boninense is able to disperse across both short and long distances. These results bring new insight into mechanisms by which G. boninense spreads in oil palm plantations. Finally, the use of approximate Bayesian computation (ABC) modelling indicates that G. boninense has undergone a demographic expansion in the past, probably before the oil palm was introduced into Southeast Asia.

Unravelling genetic diversity and cultivar parentage in the Danish apple gene bank collection

Characterization of apple germplasm is important for conservation management and breeding strategies. A set of 448 Malus domestica accessions, primarily of local Danish origin, were genotyped using 15 microsatellite markers. Ploidy levels were determined by flow cytometry. Special emphasis was given to pedigree reconstruction, cultivar fingerprinting and genetic clustering. A reference set of cultivars, mostly from other European countries, together with a private nursery collection and a small set of Malus sieversii, Malus sylvestris and small-fruited, ornamental Malus cultivars, was also included. The microsatellite markers amplified 17–30 alleles per loci with an average degree of heterozygosity at 0.78. We identified 104 (23%) duplicate genotypes including colour sports. We could infer first-degree relationships for many cultivars with previously unknown parentages. STRUCTURE analysis provided no evidence for a genetic structure but allowed us to present a putative genetic assembly that was consistent with both PCA analysis and parental affiliation. The Danish cultivar collection contains 10% duplicate genotypes including colour sports and 22% triploids. Many unique accessions and considerable genetic diversity make the collection a valuable resource within the European apple germplasm. The findings presented shed new light on the origin of Danish apple cultivars. The fingerprints can be used for cultivar identification and future management of apple genetic resources. In addition, future genome-wide association studies and breeding programmes may benefit from the findings concerning genetic clustering and diversity of cultivars.

Evaluation of a 13-loci STR multiplex system for Cannabis sativa genetic identification.

Marijuana (Cannabis sativa) is the most commonly used illicit substance in the USA. The development of a validated method using Cannabis short tandem repeats (STRs) could aid in the individualization of samples as well as serve as an intelligence tool to link multiple cases. For this purpose, a modified 13-loci STR multiplex method was optimized and evaluated according to ISFG and SWGDAM guidelines. A real-time PCR quantification method for C. sativa was developed and validated, and a sequenced allelic ladder was also designed to accurately genotype 199 C. sativa samples from 11 U.S. Customs and Border Protection seizures. Distinguishable DNA profiles were generated from 127 samples that yielded full STR profiles. Four duplicate genotypes within seizures were found. The combined power of discrimination of this multilocus system is 1 in 70 million. The sensitivity of the multiplex STR system is 0.25 ng of template DNA. None of the 13 STR markers cross-reacted with any of the studied species, except for Humulus lupulus (hops) which generated unspecific peaks. Phylogenetic analysis and case-to-case pairwise comparison of 11 cases using F st as genetic distance revealed the genetic association of four groups of cases. Moreover, due to their genetic similarity, a subset of samples (N = 97) was found to form a homogeneous population in Hardy-Weinberg and linkage equilibrium. The results of this research demonstrate the applicability of this 13-loci STR system in associating Cannabis cases for intelligence purposes.