Clinical Diagnosis and Laboratory Testing of Abnormal Appearing Toenails: A Retrospective Assessment of Confirmatory Testing for Onychomycosis in the United States, 2022-2023.

Onychomycosis is an under-recognized healthcare burden. Despite the risk of misdiagnosis, confirmatory laboratory testing is under-utilized. Histopathologic examination with polymerase chain reaction (PCR) is currently the most effective diagnostic method; it offers direct detection and identification of a fungal invasion. In this retrospective cohort study, we assessed confirmatory testing results, with matching clinical diagnoses, in 96,293 nail specimens submitted during a 9-month period from 2022 to 2023. Toenail specimens were examined using fungal culture, histopathology and/or PCR. Clinical diagnoses were identified using the International Classification of Diseases 10th Revision codes. For clinically diagnosed onychomycosis patients, the overall positivity rate was 59.4%; a similar positivity rate (59.5%) was found in patients with clinically diagnosed non-fungal nail dystrophy. Performing a histopathologic examination with PCR was more likely to provide pathogen identification results than using fungal culture. Male patients had a higher rate of onychomycosis overall; however, female patients had more non-dermatophyte mold onychomycosis caused by Aspergillus. Clinically diagnosed onychomycosis patients with a co-diagnosis of tinea pedis were more likely to test positive for onychomycosis by PCR (odds ratio [OR]: 4.2; 95% confidence interval [CI]: 2.7-6.4), histopathology (OR: 2.5; 95% CI: 2.0-3.1) and fungal culture (OR: 3.2; 95% CI: 1.5-6.6). Our results support the use of confirmatory laboratory testing when there is a clinical diagnosis of onychomycosis.

A comprehensive review of nondermatophyte mould onychomycosis: Epidemiology, diagnosis and management.

Nondermatophyte moulds (NDMs) are widely distributed and can be detected in association with mycotic nails; however, sometimes it can be challenging to establish the role of NDMs in the pathogenesis of onychomycosis (i.e. causative vs. contaminant). In studies where the ongoing invasive presence of NDMs is confirmed through repeat cultures, the global prevalence of NDMs in onychomycosis patients is estimated at 6.9% with the 3 most common genus being: Aspergillus, Scopulariopsis and Fusarium. NDM onychomycosis can, in many cases, appear clinically indistinguishable from dermatophyte onychomycosis. Clinical features suggestive of NDMs include proximal subungual onychomycosis with paronychia associated with Aspergillus spp., Fusarium spp. and Scopulariopsis brevicaulis, as well as superficial white onychomycosis in a deep and diffused pattern associated with Aspergillus and Fusarium. Longitudinal streaks seen in patients with distal and lateral onychomycosis may serve as an additional indicator. For diagnosis, light microscopic examination should demonstrate fungal filaments consistent with an NDM with at least two independent isolations in the absence of a dermatophyte; the advent of molecular testing combined with histological assessment may serve as an alternative with improved sensitivity and turnover time. In most instances, antifungal susceptibility testing has limited value. Information on effective treatments for NDM onychomycosis is relatively scarce, unlike the situation in the study of dermatophyte onychomycosis. Terbinafine and itraconazole therapy (continuous and pulsed) appear effective to varying extents for treating onychomycosis caused by Aspergillus, Fusarium or Scopulariopsis. There is scant literature on oral treatments for Neoscytalidium.

Utility of devices for onychomycosis: a review.

Onychomycosis is difficult to treat due to long treatment durations, poor efficacy rates of treatments, high relapse rates, and safety issues when using systemic antifungal agents. Device-based treatments are targeted to specific regions of the nail, have favorable safely profiles, and do not interfere with systemic agents. They may be an effective alternative therapy for onychomycosis especially with increasing reports of squalene epoxidase gene mutations and potential resistance to terbinafine therapy. In this review, we discuss four devices used as antifungal treatments and three devices used as penetration enhancers for topical agents. Lasers, photodynamic therapy, microwaves, and non-thermal plasma have the capacity to inactivate fungal pathogens demonstrated through in vivo studies. Efficacy rates for these devices, however, remain relatively low pointing toward the need to further optimize device or usage parameters. Ultrasound, nail drilling, and iontophoresis aid in improving the permeability of topical agents through the nail and have been investigated as adjunctive therapies. Due to the paucity in clinical data, their efficacy in treating onychomycosis has not yet been established. While the results of clinical studies point toward the potential utility of devices for onychomycosis, further large-scale randomized clinical trials following regulatory guidelines are required to confirm current results.

RepBox: a toolbox for the identification of repetitive elements.

BACKGROUND: Transposable elements (TEs) are short, mobile DNA elements that are known to play important roles in the genomes of many eukaryotic species. The identification and categorization of these elements is a critical task for many genomic studies, and the continued increase in the number of de novo assembled genomes demands new tools to improve the efficiency of this process. For this reason, we developed RepBox, a suite of Python scripts that combine several pre-existing family-specific TE detection methods into a single user-friendly pipeline. RESULTS: Based on comparisons of RepBox with the standard TE detection software RepeatModeler, we find that RepBox consistently classifies more elements and is also able to identify a more diverse array of TE families than the existing methods in plant genomes. CONCLUSIONS: The performance of RepBox on two different plant genomes indicates that our toolbox represents a significant improvement over existing TE detection methods, and should facilitate future TE annotation efforts in additional species.

JGI Plant Gene Atlas: an updateable transcriptome resource to improve functional gene descriptions across the plant kingdom.

Gene functional descriptions offer a crucial line of evidence for candidate genes underlying trait variation. Conversely, plant responses to environmental cues represent important resources to decipher gene function and subsequently provide molecular targets for plant improvement through gene editing. However, biological roles of large proportions of genes across the plant phylogeny are poorly annotated. Here we describe the Joint Genome Institute (JGI) Plant Gene Atlas, an updateable data resource consisting of transcript abundance assays spanning 18 diverse species. To integrate across these diverse genotypes, we analyzed expression profiles, built gene clusters that exhibited tissue/condition specific expression, and tested for transcriptional response to environmental queues. We discovered extensive phylogenetically constrained and condition-specific expression profiles for genes without any previously documented functional annotation. Such conserved expression patterns and tightly co-expressed gene clusters let us assign expression derived additional biological information to 64 495 genes with otherwise unknown functions. The ever-expanding Gene Atlas resource is available at JGI Plant Gene Atlas (https://plantgeneatlas.jgi.doe.gov) and Phytozome (https://phytozome.jgi.doe.gov/), providing bulk access to data and user-specified queries of gene sets. Combined, these web interfaces let users access differentially expressed genes, track orthologs across the Gene Atlas plants, graphically represent co-expressed genes, and visualize gene ontology and pathway enrichments.

Antifungal Resistance, Susceptibility Testing and Treatment of Recalcitrant Dermatophytosis Caused by Trichophyton indotineae: A North American Perspective on Management.

There is an ongoing epidemic of chronic, relapsing dermatophytoses caused by Trichophyton indotineae that are unresponsive to one or multiple antifungal agents. Although this new species may have originated from the Indian subcontinent, there has been a notable increase of its reporting in other countries. Based on current literature, antifungal susceptibility testing (AFST) showed a large variation of terbinafine minimum inhibitory concentrations (MICs) (0.04 to ≥ 32 µg/ml). Elevated terbinafine MICs can be attributed to mutations in the squalene epoxidase gene (single mutations: Leu393Phe, Leu393Ser, Phe397Leu, and double mutations: Leu393Phe/Ala448Thr, Phe397Leu/Ala448Thr). Itraconazole MICs had a lower range when compared with that of terbinafine (0.008-16 µg/ml, with most MICs falling between 0.008 µg/ml and < 1 µg/ml). The interpretation of AFST results remains challenging due to protocol variations and a lack of established breakpoints. Adoption of molecular methods for resistance detection, coupled with AFST, may provide a better evaluation of the in vitro resistance status of T. indotineae. There is limited information on treatment options for patients with confirmed T. indotineae infections by molecular diagnosis; preliminary evidence generated from case reports and case series points to itraconazole as an effective treatment modality, while terbinafine and griseofulvin are generally not effective. For physicians working outside of endemic regions, there is currently an unmet need for standardized clinical trials to establish treatment guidelines; in particular, combination therapy of oral and topical agents (e.g., itraconazole and ciclopirox), as well as with other azoles (i.e., fluconazole, voriconazole, ketoconazole), warrants further investigation as multidrug resistance is a possibility for T. indotineae.

The treatment of plantar warts using microwave-A review of 85 consecutive cases in the United States.

BACKGROUND: Plantar warts (verrucae plantaris) are a common source of pain for patients and are often refractory to treatment. Previous work has shown a high clearance rate of verrucae using a surface-based microwave device (Swift®). AIMS: To assess the efficacy, defined as the complete visible clearance of warts, in patients with verrucae plantaris receiving microwave treatment. PATIENTS: We undertook a retrospective review and identified records of 85 patients who underwent a course of microwave treatment at a single US-based podiatry centre. Efficacy was analyzed on the basis on intention-to-treat. RESULTS: In patients who received ≥1 session there was a complete clearance rate of 60.0% (51/85) (intention-to-treat; 59 patients completed treatment, 26 lost to follow-up) and 86.4% (51/59) per treatment completion; no significant differences in clearance rates of children and adults were observed (61.0% [25/41] vs. 59.1% [26/44]). There were 31 patients who received three sessions of microwave therapy with a clearance rate of 71.0% (22/31) as per intention-to-treat (27 patients completed treatment, 4 lost to follow-up). An average of 2.3 sessions (SD: 1.1; range: 1-6) was required for the complete clearance of plantar warts. Complete clearance was also observed in some patients with recalcitrant warts following additional treatment sessions (42.9% [3/7]). A significant reduction in wart related pain was reported for all patients undergoing treatment. Some patients continued to report a reduced amount of pain post-therapy compared with pretherapy. CONCLUSIONS: Microwave treatment of verrucae plantaris appears to be a safe and effective procedure.

Single-Point Nail Sampling to Diagnose Onychomycosis Caused by Non-Dermatophyte Molds: Utility of Polymerase Chain Reaction (PCR) and Histopathology.

The three most commonly used methods for diagnosing non-dermatophyte mold (NDM) onychomycosis are culture, polymerase chain reaction (PCR), and histopathology. Toenail samples from 512 patients (1 sample/patient) with suspected onychomycosis were examined using all three diagnostic tests. A statistically significant association was found between PCR and histopathology results, as well as between fungal culture and histopathology results. All PCR-positive and culture-positive dermatophyte samples were confirmed by histopathology. However, 15/116 (12.9%) of culture-positive NDM samples had negative histopathology results, while all PCR-positive NDM samples were confirmed by histopathology. The overall rate of dermatophyte detection was higher using PCR compared to culture (38.9% vs. 11.7%); the lower rate of NDM detection by PCR (11.7% vs. 38.9%) could be attributed to the restriction of the assay design to seven pre-selected targets. When repeat sampling in the clinic is not possible, a combination of NDM detection by PCR and positive histopathology of hyphae may be a proxy for NDM infection, particularly where the NDM occurs without a concomitant dermatophyte. There was a high degree of correlation between negative PCR and negative histopathology. A negative PCR result with negative histopathology findings may be a reliable proxy for the diagnosis of non-fungal dystrophy.

Detection of Squalene Epoxidase Mutations in United States Patients with Onychomycosis: Implications for Management.

Resistance to oral terbinafine, the most commonly used antifungal to treat dermatophytosis and onychomycosis worldwide, is being increasingly reported. In this study, we aimed to investigate the species distribution and prevalence of squalene epoxidase mutations among toenail dermatophyte isolates. Samples from 15,683 patients suspected of onychomycosis visiting the offices of dermatologists and podiatrists in the United States were analyzed. Clinical information was reviewed, and dermatophyte species with or without squalene epoxidase mutations were detected using multiplex real-time PCRs. The frequency of dermatophytes was 37.6%; of isolates belonging to the Trichophyton genus, 88.3% were the T. rubrum complex, and 11.2% were the T. mentagrophytes complex. Individuals aged >70 years exhibited higher infection rates for the T. mentagrophytes complex. The overall mutation rate among Trichophyton spp. was 3.7%, with a higher mutation rate detected in the T. mentagrophytes complex (4.3 vs. 3.6%). Commonly detected mutations were T1189C/Phe397Leu (34.5%), T1306C/Phe415Ser (16.0%), and C1191A/Phe397Leu (11.0%). Squalene epoxidase gene mutations associated with decreased terbinafine susceptibility have been identified in United States patients with toenail onychomycosis. Physicians should be aware of the risk factors for resistance development and engage in antifungal stewardship practices such as directed diagnosis and treatment of dermatophytosis and onychomycosis.

Combatting antifungal resistance: Paradigm shift in the diagnosis and management of onychomycosis and dermatomycosis.

Antifungal resistance has become prevalent worldwide. Understanding the factors involved in spread of resistance allows the formulation of strategies to slow resistance development and likewise identify solutions for the treatment of highly recalcitrant fungal infections. To investigate the recent explosion of resistant strains, a literature review was performed focusing on four main areas: mechanisms of resistance to antifungal agents, diagnosis of superficial fungal infections, management, and stewardship. The use of traditional diagnostic tools such as culture, KOH analysis and minimum inhibitory concentration values on treatment were investigated and compared to the newer techniques such as molecular methods including whole genome sequencing, and polymerase chain reaction. The management of terbinafine-resistant strains is discussed. We have emphasized the need for antifungal stewardship including increasing surveillance for resistant infection.

Factors Associated With Musculoskeletal Pain Among Hair Transplant Surgeons: Analyses of Survey Data and Review of the Literature.

BACKGROUND: The prevalence of work-related musculoskeletal disorders (WRMD) is increasing among all surgical specialties. OBJECTIVE: Results of a cross-sectional survey of hair transplant surgeons were analyzed, with the aims to (1) determine the prevalence of WRMD, (2) assess risk factors associated with musculoskeletal (MSK) symptoms, and (3) identify mitigation measures. MATERIALS AND METHODS: A survey pertaining to demographics, MSK-related symptoms and its impacts, and pain mitigation measures taken, if any, were distributed to 834 hair transplant surgeons. Risk factors associated with pain severity were assessed using linear regression. RESULTS: Overall, 78.5% (73 of 93) respondents had experienced pain when performing surgery. Musculoskeletal symptoms were most severe in the neck, followed by upper/lower back, and extremities. Number of grafts performed per session of follicular unit extraction positively correlated with pain severity; female surgeons and surgeons aged >71 years were at higher risk. A majority expressed concern that WRMD may limit their career and agreed to a need for improved workplace education. Strength training and ergonomic improvements of surgical procedure were not commonly adopted. CONCLUSION: In sum, WRMD can be debilitating in health care professionals. Workplace ergonomic adjustments and physical exercise programs may be warranted to better mitigate MSK symptoms.

The emergence of Trichophyton indotineae: Implications for clinical practice.

Emergence and increase of terbinafine-resistant dermatophytosis led to the identification of Trichophyton mentagrophytes internal transcriber space (ITS) genotype VIII in 2017, later renamed as Trichophyton indotineae and classified as a separate species in 2020. With its suspected origin in South Asia, this novel strain has emerged in Bahrain, Canada, Denmark, Finland, France, Germany, India, Iran, Japan, Russia, and Switzerland, with its spread attributed primarily to travel and migration. Diagnosis using routine mycology laboratory techniques is unable to distinguish T. indotineae from T. mentagrophytes and T. interdigitale; specific identification requires genomic sequencing to identify unique, specific markers. One speculated reason for this recent outbreak is the unrestricted use of topical steroid creams and antifungal agents. Patients with extensive tinea corporis and cruris due to T. indotineae present with inflammatory red plaques in multiple body sites. The majority of these infections prove to be resistant to conventional antifungals, including allylamines and azoles (itraconazole and fluconazole), thus emphasizing the need for antifungal susceptibility testing before treatment initiation and for reassessing in nonresponsive patients. Molecular studies have identified several point mutations in the ERG1 (terbinafine resistance) and ERG11 (azole resistance) genes, which need to be analyzed further. Use of relatively new agents, such as voriconazole and luliconazole, as well as device modalities and combination therapy, could be investigated for recalcitrant T. indotineae infections.

Strategies for the enhancement of nail plate permeation of drugs to treat onychomycosis.

Onychomycosis is caused by dermatophytes, non-dermatophytes and yeasts. It has a global prevalence of 5.5%, requires long treatment periods, and has high relapse rates following therapy. Oral antifungals are generally the most common treatment. While effective, they have limitations such as drug-drug interactions, hepatotoxicity and adverse side effects; thus, they cannot be used in several populations. Topical antifungals do not have the safety limitations but are typically not as effective. The primary challenge of topical treatment is the permeation of drug molecules across the nail plate barrier, which is a highly cross-linked keratin network. The use of drugs and formulations with favourable characteristics such as small size, absence of lipophilicity, hydrophilic nature, hydrating properties and appropriate pH can greatly improve permeation. Here, we review physical, nanoparticle-based, formulation-based, mechanical and chemical drug delivery strategies to improve the permeation of drugs across the nail plate.

Dermatophytomas: Clinical Overview and Treatment.

Dermatophytomas are characterized as a hyperkeratotic fungal mass in the subungual space, showing as dense white or yellow, typically in longitudinal streaks or patches. Masses can be visualized by traditional microscopy or histology. Newer technologies such as dermoscopy and optical coherence tomography also provide visual features for dermatophytoma diagnosis. The density of fungal mass, and lack of adherence to the nail structures, as well as possible biofilm development, may play a role in the reduction in drug penetration and subsequent lack of efficacy with traditional oral therapies such as terbinafine and itraconazole. A combination of drug treatment with mechanical or chemical debridement/avulsion has been recommended to increase efficacy. The topical antifungal solutions such as tavaborole, efinaconazole, and luliconazole may reach the dermatophytoma by both the transungual and subungual routes, due to low affinity for keratin and low surface tension. Current data indicates these topicals may provide efficacy for dermatophytoma treatment without debridement/avulsion. Similarly, fosravuconazole (F-RVCZ) has an improved pharmacological profile versus ravuconazole and may be an improved treatment option versus traditional oral therapies. The availability of improved treatments for dermatophytomas is crucial, as resistance to traditional therapies is on the increase.

Diagnosing Onychomycosis: What's New?

An overview of the long-established methods of diagnosing onychomycosis (potassium hydroxide testing, fungal culture, and histopathological examination) is provided followed by an outline of other diagnostic methods currently in use or under development. These methods generally use one of two diagnostic techniques: visual identification of infection (fungal elements or onychomycosis signs) or organism identification (typing of fungal genus/species). Visual diagnosis (dermoscopy, optical coherence tomography, confocal microscopy, UV fluorescence excitation) provides clinical evidence of infection, but may be limited by lack of organism information when treatment decisions are needed. The organism identification methods (lateral flow techniques, polymerase chain reaction, MALDI-TOF mass spectroscopy and Raman spectroscopy) seek to provide faster and more reliable identification than standard fungal culture methods. Additionally, artificial intelligence methods are being applied to assist with visual identification, with good success. Despite being considered the 'gold standard' for diagnosis, clinicians are generally well aware that the established methods have many limitations for diagnosis. The new techniques seek to augment established methods, but also have advantages and disadvantages relative to their diagnostic use. It remains to be seen which of the newer methods will become more widely used for diagnosis of onychomycosis. Clinicians need to be aware of the limitations of diagnostic utility calculations as well, and look beyond the numbers to assess which techniques will provide the best options for patient assessment and management.

Utility of polymerase chain reaction for assessment of onychomycosis during topical therapy.

BACKGROUND: Increased detection of fungi including non-dermatophyte molds (NDMs) using polymerase chain reaction (PCR) methods is well-established. However, the use of PCR to evaluate ongoing onychomycosis treatment outcome has not been investigated. METHODS: Nail samples from 28 patients receiving topical efinaconazole were evaluated by both KOH/culture and PCR methods across the study period. Detection of microorganisms by PCR was compared to the culture at baseline and end of study at month 24 (M24). Fungal detection by both methods was evaluated with respect to clinical cure observed as 100% visual clearance of the target toenail. RESULTS: By culture, all 28 subjects were dermatophyte-positive at pre-treatment; only 4/28 also exhibited an NDM microorganism. According to PCR, 24/28 subjects were dermatophyte-positive pre-treatment, with 25/28 also exhibiting NDMs. At M24, 18/28 (64.3%) participants had negative KOH/culture results, in contrast to 4/28 (14.3%) negative PCR results. PCR showed higher rates of NDM detection than the culture at baseline as well as M24. Calculations to compare the diagnostic utility of KOH/culture versus PCR found that positive tests with both methods reliably indicate the presence of onychomycosis, but negative PCR correlated better with onychomycosis cure than did KOH/culture. DISCUSSION: PCR confirmed a high presence of NDMs pre-treatment, and continued presence of NDMs to M24, with unknown significance requiring further investigation. Though both KOH/culture and PCR have diagnostic limitations, PCR showed better overall utility than culture in predicting onychomycosis topical treatment outcome and should be more strongly considered for evaluation of topical therapies.

Ten new high-quality genome assemblies for diverse bioenergy sorghum genotypes.

Introduction: Sorghum (Sorghum bicolor (L.) Moench) is an agriculturally and economically important staple crop that has immense potential as a bioenergy feedstock due to its relatively high productivity on marginal lands. To capitalize on and further improve sorghum as a potential source of sustainable biofuel, it is essential to understand the genomic mechanisms underlying complex traits related to yield, composition, and environmental adaptations. Methods: Expanding on a recently developed mapping population, we generated de novo genome assemblies for 10 parental genotypes from this population and identified a comprehensive set of over 24 thousand large structural variants (SVs) and over 10.5 million single nucleotide polymorphisms (SNPs). Results: We show that SVs and nonsynonymous SNPs are enriched in different gene categories, emphasizing the need for long read sequencing in crop species to identify novel variation. Furthermore, we highlight SVs and SNPs occurring in genes and pathways with known associations to critical bioenergy-related phenotypes and characterize the landscape of genetic differences between sweet and cellulosic genotypes. Discussion: These resources can be integrated into both ongoing and future mapping and trait discovery for sorghum and its myriad uses including food, feed, bioenergy, and increasingly as a carbon dioxide removal mechanism.

Genomic patterns of structural variation among diverse genotypes of Sorghum bicolor and a potential role for deletions in local adaptation.

Genomic structural mutations, especially deletions, are an important source of variation in many species and can play key roles in phenotypic diversification and evolution. Previous work in many plant species has identified multiple instances of structural variations (SVs) occurring in or near genes related to stress response and disease resistance, suggesting a possible role for SVs in local adaptation. Sorghum [Sorghum bicolor (L.) Moench] is one of the most widely grown cereal crops in the world. It has been adapted to an array of different climates as well as bred for multiple purposes, resulting in a striking phenotypic diversity. In this study, we identified genome-wide SVs in the Biomass Association Panel, a collection of 347 diverse sorghum genotypes collected from multiple countries and continents. Using Illumina-based, short-read whole-genome resequencing data from every genotype, we found a total of 24,648 SVs, including 22,359 deletions. The global site frequency spectrum of deletions and other types of SVs fit a model of neutral evolution, suggesting that the majority of these mutations were not under any types of selection. Clustering results based on single nucleotide polymorphisms separated the genotypes into eight clusters which largely corresponded with geographic origins, with many of the large deletions we uncovered being unique to a single cluster. Even though most deletions appeared to be neutral, a handful of cluster-specific deletions were found in genes related to biotic and abiotic stress responses, supporting the possibility that at least some of these deletions contribute to local adaptation in sorghum.

De novo identification and targeted sequencing of SSRs efficiently fingerprints Sorghum bicolor sub-population identity.

Recent plant breeding studies of several species have demonstrated the utility of combining molecular assessments of genetic distance into trait-linked SNP genotyping during the development of parent lines to maximize yield gains due to heterosis. SSRs (Short Sequence Repeats) are the molecular marker of choice to determine genetic diversity, but the methods historically used to sequence them have been burdensome. The ability to analyze SSRs in a higher-throughput manner independent of laboratory conditions would increase their utility in molecular ecology, germplasm curation, and plant breeding programs worldwide. This project reports simple bioinformatics methods that can be used to generate genome-wide de novo SSRs in silico followed by targeted Next Generation Sequencing (NGS) validation of those that provide the most information about sub-population identity of a breeding line, which influences heterotic group selection. While these methods were optimized in sorghum [Sorghum bicolor (L.) Moench], they were developed to be applied to any species with a reference genome and high-coverage whole-genome sequencing data of individuals from the sub-populations to be characterized. An analysis of published sorghum genomes selected to represent its five main races (bicolor, caudatum, durra, kafir, and guinea; 75 accessions total) identified 130,120 SSR motifs. Average lengths were 23.8 bp and 95% were between 10 and 92 bp, making them suitable for NGS. Validation through targeted sequencing amplified 188 of 192 assayed SSR loci. Results highlighted the distinctness of accessions from the guinea sub-group margaritiferum from all other sorghum accessions, consistent with previous studies of nuclear and mitochondrial DNA. SSRs that efficiently fingerprinted margaritiferum individuals (Xgma1 -Xgma6) are presented. Developing similar fingerprints of other sub-populations (Xunr1 -Xunr182) was not possible due to the extensive admixture between them in the data set analyzed. In summary, these methods were able to fingerprint specific sub-populations when rates of admixture between them are low.