Comparison of DNA Microarray,Loop-Mediated Isothermal Amplification (LAMP) and Real-Time PCR with DNA Sequencing for Identification of <Emphasis Type="Italic">Fusarium</Emphasis> spp. Obtained from Patients with Hematologic Malignancies

The performance of three molecular biology techniques, i.e., DNA microarray, loop-mediated isothermal amplification (LAMP), and real-time PCR were compared with DNA sequencing for properly identification of 20 isolates of Fusarium spp. obtained from blood stream as etiologic agent of invasive infections in patients with hematologic malignancies. DNA microarray, LAMP and real-time PCR identified 16 (80%) out of 20 samples as Fusarium solani species complex (FSSC) and four (20%) as Fusarium spp. The agreement among the techniques was 100%. LAMP exhibited 100% specificity, while DNA microarray, LAMP and real-time PCR showed 100% sensitivity. The three techniques had 100% agreement with DNA sequencing. Sixteen isolates were identified as FSSC by sequencing, being five Fusarium keratoplasticum, nine Fusarium petroliphilum and two Fusarium solani. On the other hand, sequencing identified four isolates as Fusarium non-solani species complex (FNSSC), being three isolates as Fusarium napiforme and one isolate as Fusarium oxysporum. Finally, LAMP proved to be faster and more accessible than DNA microarray and real-time PCR, since it does not require a thermocycler. Therefore, LAMP signalizes as emerging and promising methodology to be used in routine identification of Fusarium spp. among cases of invasive fungal infections.     

Global Distribution of Two Fungal Pathogens Threatening Endangered Sea Turtles

Nascent fungal infections are currently considered as one of the main threats for biodiversity and ecosystem health, and have driven several animal species into critical risk of extinction. Sea turtles are one of the most endangered groups of animals and only seven species have survived to date. Here, we described two pathogenic species, i.e., Fusarium falciforme and Fusarium keratoplasticum, that are globally distributed in major turtle nesting areas for six sea turtle species and that are implicated in low hatch success. These two fungi possess key biological features that are similar to emerging pathogens leading to host extinction, e.g., high virulence, and a broad host range style of life. Their optimal growth temperature overlap with the optimal incubation temperature for eggs, and they are able to kill up to 90% of the embryos. Environmental forcing, e.g., tidal inundation and clay/silt content of nests, were correlated to disease development. Thus, these Fusarium species constitute a major threat to sea turtle nests, especially to those experiencing environmental stressors. These findings have serious implications for the survival of endangered sea turtle populations and the success of conservation programs worldwide.     

Molecular characterization of pathogenic Fusarium species in cucurbit plants from Kermanshah province, Iran

Fusarium is one of the important phytopathogenic genera of microfungi causing serious losses on cucurbit plants in Kermanshah province, the largest area of cucurbits plantation in Iran. Therefore, the objectives in this study were to isolate and identify disease-causing Fusarium spp. from infected cucurbit plants, to ascertain their pathogenicity, and to determine their phylogenetic relationships. A total of 100 Fusarium isolates were obtained from diseased cucurbit plants collected from fields in different geographic regions in Kermanshah province, Iran. According to morphological characters, all isolates were identified as Fusarium oxysporum, Fusarium proliferatum, Fusarium equiseti, Fusarium semitectum and Fusarium solani. All isolates of the five Fusarium spp. were evaluated for their pathogenicity on healthy cucumber (Cucumis sativus) and honeydew melon (Cucumis melo) seedlings in the glasshouse. F. oxysporum caused damping-off in 20–35 days on both cucurbit seedlings tested. Typical stem rot symptoms were observed within 15 days after inoculation with F. solani on both seedlings. Based on the internal transcribed spacer (ITS) regions of ribosomal DNA (rDNA) restriction fragment length polymorphism (RFLP) analysis, the five Fusarium species were divided into two major groups. In particular, isolates belonging to the F. solani species complex (FSSC) were separated into two RFLP types. Grouping among Fusarium strains derived from restriction analysis was in agreement with criteria used in morphological classification. Therefore, the PCR-ITS-RFLP method provides a simple and rapid procedure for the differentiation of Fusarium strains at species level. This is the first report on identification and pathogenicity of major plant pathogenic Fusarium spp. causing root and stem rot on cucurbits in Iran.     

Rapid Identification of Four Fusarium spp. Complex by High-Resolution Melting Curve Analysis and their Antifungal Susceptibility Profiles

Fusarium species are globally distributed filamentous ascomycete fungi that are frequently reported as plant pathogens and opportunistic human pathogens, leading to yield loss of crops, mycotoxin contamination of food and feed products as well as damage to human and livestock. Human infections of Fusarium spp. are difficult to treat due to broad antifungal resistance by members of this genus. Their role as disease-causing agents in crops and humans suggests a need for antifungal resistance profiles as well as a simple, rapid, and cost effective identification method. Fusarium strains were isolated from food and clinical samples. High-resolution melting curve (HRM) analysis was performed using specific primers targeting internal transcribed spacer (ITS) region, followed with evaluation of specificity and sensitivity. The antifungal susceptibility of four Fusarium species was studied using the Sensititre YeastOne method. HRM analysis revealed reproducible, unimodal melting profiles specific to each of the four Fusarium strains, while no amplification of the negative controls. The minimum detection limits were 100–120 copies based on a 2 µl volume of template. Clear susceptibility differences were observed against antifungal agents by different Fusarium isolates, with amphotericin B and voriconazole displayed strongest antifungal effects to all the tested strains. We developed a simple, rapid, and low-cost qPCR-HRM method for identification of four Fusarium spp. (F. oxysporum, F. lateritium, F. fujikuroi, and F. solani). The antifungal susceptibility profiles supplied antifungal information of foodborne and clinical Fusarium spp. and provided guidance for clinical treatment of human infections.

     

Prospects of molecular markers in <Emphasis Type="Italic">Fusarium</Emphasis> species diversity

Recent developments in genomics have opened up for newer opportunities to study the diversity and classification of fungi. The genus Fusarium contains many plant pathogens that attack diverse agricultural crops. Fusarium spp. are not only pathogenic to plants but are also known as toxin producers that negatively affect animal and human health. The identification of Fusarium species still remains one of the most critical issues in fungal taxonomy, given that the number of species recognized in the genus has been constantly changing in the last century due to the different taxonomic systems. This review focuses of various molecular-based techniques employed to study the diversity of Fusarium species causing diseases in major food crops. An introduction of fusarial diseases and their mycotoxins and molecular-marker-based methods for detection introduce the concept of marker application. Various well-known molecular techniques such as random amplified polymorphic DNA, amplification fragment length polymorphism, etc. to more modern ones such as DNA microarrays, DNA barcoding, and pyrosequencing and their application form the core of the review. Target regions in the genome which can be potential candidates for generation of probes and their use in phylogeny of Fusarium spp. are also presented. The concluding part emphasizes the value of molecular markers for assessing genetic variability and reveals that molecular tools are indispensable for providing information not only of one Fusarium species but on whole fungal community. This will be of extreme value for diagnosticians and researchers concerned with fungal biology, ecology, and genetics.     

Mating Type Sequences in Asexually Reproducing Fusarium Species

To assess the potential for mating in several Fusarium species with no known sexual stage, we developed degenerate and semidegenerate oligonucleotide primers to identify conserved mating type (MAT) sequences in these fungi. The putative α and high-mobility-group (HMG) box sequences from Fusarium avenaceum, F. culmorum, F. poae, and F. semitectum were compared to similar sequences that were described previously for other members of the genus. The DNA sequences of the regions flanking the amplified MAT regions were obtained by inverse PCR. These data were used to develop diagnostic primers suitable for the clear amplification of conserved mating type sequences from any member of the genus Fusarium. By using these diagnostic primers, we identified mating types of 122 strains belonging to 22 species of Fusarium. The α box and the HMG box from the mating type genes are transcribed in F. avenaceum, F. culmorum, F. poae, and F. semitectum. The novelty of the PCR-based mating type identification system that we developed is that this method can be used on a wide range of Fusarium species, which have proven or expected teleomorphs in different ascomycetous genera, including Calonectria, Gibberella, and Nectria.     

A multiplex real-time PCR method using hybridization probes for the detection and the quantification of Fusarium proliferatum, F. subglutinans, F. temperatum, and F. verticillioides

Maize contamination with Fusarium species is one of the major sources of mycotoxins in food and feed derivates. In the present study, a LightCycler^® real-time PCR method using hybridization probes was developed for the specific identification, detection, and quantification of Fusarium proliferatum, Fusarium subglutinans, Fusarium temperatum, and Fusarium verticillioides, four mycotoxin-producing pathogens of maize. Primers and hybridization probes were designed to target the translation elongation factor 1α (EF-1α) gene of F. subglutinans and F. temperatum or the calmodulin (Cal) gene of F. proliferatum and F. verticillioides. The specificity of the real-time PCR assays was confirmed for the four Fusarium species, giving no amplification with DNA from other fungal species commonly recovered from maize. The assays were found to be sensitive, detecting down to 5 pg and 50 pg of Fusarium DNA in simplex and multiplex conditions respectively, and were able to quantify pg-amounts of Fusarium DNA in artificially Fusarium-contaminated maize samples. The real-time PCR method developed provides a useful tool for routine identification, detection, and quantification of toxigenic Fusarium species in maize.     

Novel DNA markers for taxonomic characterization and identification of <Emphasis Type="Italic">Fusarium</Emphasis> species

Ten Fusarium sporotrichioides strains from different geographic regions were analyzed by RAPD in order to detect DNA loci potentially suitable as new markers for taxonomic characterization and identification of toxigenic Fusarium fungi. Three monomorphic fragments were selected from PCR amplificates obtained with one of the standard RAPD primers and sequenced. Analysis of the sequences enabled the development of specific SCAR markers for identification of Fusarium fungi at the level of species groups characterized by similar profiles of produced mycotoxins.     

Unravelling the Microbiome of Eggs of the Endangered Sea Turtle Eretmochelys imbricata Identifies Bacteria with Activity against the Emerging Pathogen Fusarium falciforme

Habitat bioaugmentation and introduction of protective microbiota have been proposed as potential conservation strategies to rescue endangered mammals and amphibians from emerging diseases. For both strategies, insight into the microbiomes of the endangered species and their habitats is essential. Here, we sampled nests of the endangered sea turtle species Eretmochelys imbricata that were infected with the fungal pathogen Fusarium falciforme. Metagenomic analysis of the bacterial communities associated with the shells of the sea turtle eggs revealed approximately 16,664 operational taxonomic units, with Proteobacteria, Actinobacteria, Firmicutes and Bacteroidetes as the most dominant phyla. Subsequent isolation of Actinobacteria from the eggshells led to the identification of several genera (Streptomyces, Amycolaptosis, Micromomospora Plantactinospora and Solwaraspora) that inhibit hyphal growth of the pathogen F. falciforme. These bacterial genera constitute a first set of microbial indicators to evaluate the potential role of microbiota in conservation of endangered sea turtle species.     

Fusarium genomic resources: Tools to limit crop diseases and mycotoxin contamination

It has been almost 10 years since Joan Bennett suggested that fungal biologists create a “wish list” for fungal genome sequences (Bennett JW. White paper: Genomics for filamentous fungi. Fungal Genet Biol 1997; 21: 3–7). The availability of over 200 review papers concerning fungal genomics is a reflection of significant progress with a diversity of fungal species. Although much progress has been made, the use of genomic data to study mycotoxin synthesis and function, pathogenesis and other aspects of fungal biology is in its infancy. Here, we briefly present the status of publicly available genomic resources for Fusarium, a genus of important plant pathogenic and mycotoxin-producing fungi of worldwide concern. Preliminary examination of microarray data collected from F. verticillioides liquid cultures provides evidence of widespread differential gene expression over time.     

Refractory disseminated fusariosis by Fusarium verticillioides in a patient with acute myeloid leukaemia relapsed after allogeneic hematopoietic stem cell transplantation: A case report and literature review

BackgroundFusarium species are among the leading fungal pathogens to cause invasive mould infections in patients with hematopoietic malignancy. The Fusarium species most frequently involved in human infections are Fusarium solani, Fusarium oxysporum and Fusarium verticillioides. However, identification is a cumbersome and time-consuming task. Fusarium is resistant in vitro to many of the antifungal agents and the management of fusariosis is not well defined.ObjectivesTo emphasise the difficulty of identifying Fusarium spp. by conventional methods and the need of new rapid molecular tests to achieve earlier diagnosis and appropriate therapy.MethodsA disseminated Fusarium infection due to F. verticillioides was documented in a neutropenic refractory patient with acute myeloid leukaemia, relapsed after allogeneic hematopoietic stem cell transplantation.ResultsThe patient died despite liposomal amphotericin B and voriconazole combination and “in vitro” susceptibility of agents employed. Morphological and molecular identification of F. verticillioides was obtained only after the death of the patient.ConclusionsThis case highlights the poor outcome of an invasive fungal disease caused by Fusarium in aplastic patients. Identification of members of Fusarium genus remains restricted to selected laboratories and should be introduced into routine mycological diagnostics. In immunocompromised patients, diagnosis of fusariosis is directly related to prompt diagnosis and to patient's status. Current diagnosis methods and therapeutic options are discussed.     

Real-time PCR Assay Based on Topoisomerase-II Gene for Detection of <Emphasis Type="Italic">Fusarium udum</Emphasis>

Fusarium wilt is an important soilborne disease of pigeonpea, caused by Fusarium udum. In this study, we have designed a real-time PCR assay for the detection of Fusarium udum from infected pigeonpea plants. Based on Topoisomerase-II gene sequence data from Fusarium udum and other related Fusarium species, a pair of primer was designed. The species-specific primers were tested in real-time PCR SYBR green assay. No increasing fluorescence signals exceeding the baseline threshold was observed with tested microbes, except Fusarium udum DNA. A single dissociation peak of increased fluorescence was obtained for the specific primers at melting temperature of 81.25°C. The real-time PCR showed a lowest detection of 0.1 pg genomic DNA. The assay was more sensitive, accurate and less time consuming for detection of Fusarium udum in infected plants root.     

The strain HEB01 of Fusarium sp., a new pathogen that infects brown soft scale

The objectives of the present study were to identify a fungal strain, HEB01, isolated from naturally infected brown soft scale, Coccus hesperidum L. (Hemiptera: Coccidae), and to determine whether it is an entomopathogenic fungus. Fungal culture, reinoculation test, morphological observations, and infection behaviors were investigated. Additionally, the fungal gene sequence of translation elongation factor 1-a (EF-1a) was obtained for molecular identification. The results showed that the fungal strain HEB01 belongs to the Fusarium incarnatum-equiseti species complex and is part of the family Nectriaceae (Hypocreales: Sordariomycetes). The inoculation test and observations of infection behaviors indicated that strain HEB01 is a pathogenic fungus and confirmed that it infects brown soft scale. Thus, the HEB01 strain of Fusarium incarnatum-equiseti is the first pathogen in the genus Fusarium to be isolated from a brown soft scale.     

Real-time PCR detection and quantification of Fusarium poae,F. graminearum,F. sporotrichioides and F. langsethiae in cereal grains in Finland and Russia

Abstract

TaqMan real-time quantitative PCR assays were developed for the accurate detection and quantification of DNA from Fusarium poae and F. graminearum species, which are able to produce trichothecenes. These and other PCR assays were used for the quantification of trichothecene-producing Fusarium fungi in cereal grains. A correlation was found between the levels of F. poae DNA and nivalenol and enniatins in barley and between the levels of F. graminearum DNA and deoxynivalenol in oats. The correlations between F. poae DNA and nivalenol and F. graminearum DNA and deoxynivalenol levels were higher than those between these mycotoxins and morphologically determined F. poae and F. graminearum/F. culmorum contamination levels. The use of F. poae specific primers and probe together with F. sporotrichioides/F. langsethiae specific primers and probe in a multiplex qPCR assay yielded results in accordance with those obtained using these primers and probes separately.     

Seasonal variations of Fusarium species in wheat fields in Upper Egypt

Abstract

Populations of the genus Fusarium in wheat fields were studied within the crop-growing season at Qena area (Upper Egypt) using two different types of media (DCPA and DRBA) at 25°C. Fourteen Fusarium species were isolated during this study, namely F. anthophilum, F. aquaeductuum, F. chlamdosporum, F. dimerum, F. merismoides, F. moniliforme, F. oxysporum, F. poae, F. proliferatum, F. sambucinum, F. scripi, F. solani, F. sporotrichioides and F. subglutinans. Fusarium merismoides, F. oxysporum and F. sambucinum were the most common Fusarium species isolated from different wheat plant parts (rhizosphere and rhizoplane) as well as from the wheat fields (soil and air). Fusarium spp. rarely appeared at the beginning of the season and increased sharply between January to March and decreased slightly or sharply at the end of the season according to the type of media and isolation source.     

Molecular identification and determination of the trichothecene chemotypes of fungi causing crown and root in different growth stages of wheat in north of Iran

In order to determine the crown and root agents and their mycotoxins produced in different growth stages of wheat including seedling, tillering and heading, sampling was done in north of Iran, during 2011–2012. From 160 isolates of Fusarium, eight species were obtained including F. graminearum, F. culmorum, F. equiseti, F. nygamai, F. semitectum, F. solani, F. acuminatum and F. oxysporum. Sampling at different growth stages showed that F. graminearum was the predominant causal agent of crown and root at the heading stage, whereas other species of Fusarium were mostly observed at the seedling and tillering stages. Moreover, identification of pathogenic species was confirmed using species-specific primers pairs. In F. graminearum isolates, presence of Tri13 gene, responsible for nivalenol (NIV) and deoxynivalenol (DON) mycotoxins biosynthesis, was detected using specific PCR primers. Finally, the ability of trichothecene production of five F. graminearum isolates was confirmed with high-performance liquid chromatography.     

Occurrence and Pathogenicity of Fusarium Species in Banana Fruits

Banana fruits were studied over a six-month period in order to determine the incidence of species of the Fusarium genus and assess their potential pathogenicity. The 72 samples studied were commercially available in Italy and Spain, where they were brought from Panama, Ecuador and Canary Islands. Among the species detected in the fruits, Fusarium semitectum var. majus Wollenw. was predominant, followed by F. moniliforme Sheld., F. solani (Mart.) Appel & WoUenw., F. oxysporum Schlecht., F. proliferatum (Matsushima) Nirenberg, F. graminearum Schw., F. camptoceras WoUenw. &C Reinking, F. subglutinans (WoUenw. & Reinking) Nelson et al., F. dimerum Penzig in Sacc, F. acuminatum EU. & Ev., and F. equiseti (Corda) Sacc. Fusarium proliferatum had never been reported to occur as contaminating fungi in banana fruits to date. Fusarium subglutinans, F. acuminatum and F. graminearum were found to be the most markedly pathogenic of all. The lack of noticeable differences in relation to the incidence of the different species isolated from the samples indicates that the mycoflora found is typical of this fruit and does not depend on its origin.     

Mycobiota of the Takamatsuzuka and Kitora Tumuli in Japan,focusing on the molecular phylogenetic diversity of <Emphasis Type="Italic">Fusarium</Emphasis> and <Emphasis Type="Italic">Trichoderma</Emphasis>

In an effort to clarify the cause of the deterioration of the colorfully painted murals that adorn the inner walls of the small stone chambers in the Takamatsuzuka and Kitora Tumuli in Japan, we enumerated the fungi that were isolated from moldy spots on the plaster walls collected between May 2004 and April 2005. The 262 fungal isolates from 79 samples of both tumuli were identified as approximately 100 species based on their phenotypic characters. Fusarium, Trichoderma, and Penicillium species were the predominant colonizers in the stone chamber interior and adjacent areas of both tumuli. In addition to the 28S phylogeny, neighbor-joining and Bayesian phylogenies of partial EF-1-alpha gene sequences revealed 24 genetically diverse fusaria in the Takamatsuzuka and Kitora Tumuli. Most of the fusaria were nested in clade 3 of the Fusarium solani species complex (FSSC); however, a few isolates were members of the F. oxysporum species complex (FOSC) clade or the F. avenaceum/F. tricinctum species complex clade. The FSSC isolates were compared with those detected in the Lascaux cave in France. In addition, a partial EF-1α gene phylogeny indicated that 13 Trichoderma isolates clustered in the Harzianum-Virens clade and 5 isolates in the Viride clade or Trichoderma sect. Longibrachiatum. Our analyses suggest that most of the fungi recovered from both tumuli are typically soil dwellers. First two authors contributed equally to this work     

Multiplex PCR assay for the identification of nivalenol, 3- and 15-acetyl-deoxynivalenol chemotypes in Fusarium

The ability to rapidly distinguish trichothecene chemotypes in a given species/population of the genus Fusarium is important due to significant differences in the toxicity of these secondary metabolites. A multiplex PCR assay, based on primer pairs derived from the Tri3, Tri5 and Tri7 genes of the trichothecene gene cluster was established for the identification of the different chemotypes among Fusarium graminearum, F. culmorum and F. cerealis. Using the selected primers, specific amplification products of 625, 354 and 708 bp were obtained from Fusarium isolates producing nivalenol, 3-acetyl-deoxynivalenol and 15-acetyl-deoxynivalenol, respectively. Moreover, the multiplex PCR was successfully used to identify the chemotype of the Fusarium species contaminating wheat kernels. Four picograms of fungal DNA were found to be necessary to obtain a visible amplification product.