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Many recent articles feature research on the Fusarium tricinctum species complex (FTSC), and their authors present different ideas on how the isolates of this species complex can be identified at the species level. In previous studies, our aim was to investigate the phylogeny of FTSC strains, which researchers have morphologically identified as Fusarium avenaceum, Fusarium arthrosporioides, and Fusarium anguioides. In the current study, our phylogenetic maximum parsimony and likelihood analyses of the DNA sequences of the translation elongation factor 1-alpha (TEF1) and combined sequences of TEF1 and beta-tubulin (TUB2) supported the existence of at least four main groups among these strains. Main Group I mainly contains F. avenaceum strains, while Main Group II contains two subgroups, one of which primarily includes F. arthrosporioides strains, and the other mainly includes European F. anguioides strains. Main Group III contains strains from different plants that originated from Asia, including two F. anguioides strains. F. avenaceum strains, which are mostly isolated from different trees, form Main Group IV. A fifth group (Main Group V) was only supported by TEF1 sequences. The main groups previously found by us based on TUB2 sequences could be connected to the new species of the FTSC, which were identified based on TEF1 sequences. In addition, we found strains that significantly differ from Main Groups I-V, and we grouped some of them as single, intermediate, or sister groups. All of the main groups of the present work, and some single and intermediate strains, may represent different species of the FTSC, while the two subgroups of Main Group II constitute intraspecific variation. Regardless of whether they belonged to the main groups, all the analysed strains were able to form different enniatins and 2-amino-14,16-dimethyloctadecan-3-ol, but did not produce beauvericin. [ABSTRACT FROM AUTHOR]

In summer 2019, during a survey on the health status of a hazelnut orchard located in the Tuscia area (the province of Viterbo, Latium, Italy), nuts showing symptoms, such as brown-grayish spots at the bottom of the nuts progressing upward to the apex, and necrotic patches on the bracts and, sometimes, on the petioles, were found and collected for further studies. This syndrome is associated with the nut gray necrosis (NGN), whose main causal agent is Fusarium lateritium. Aiming to increase knowledge about this fungal pathogen, the whole-genome sequencing of a strain isolated from symptomatic hazelnut was performed using long Nanopore reads technology in combination with the higher precision of the Illumina reads, generating a high-quality genome assembly. The following phylogenetic and comparative genomics analysis suggested that this isolate is caused by the F. tricinctum species complex rather than F. lateritium one, as initially hypothesized. Thus, this study demonstrates that different Fusarium species can infect Corylus avellana producing the same symptomatology. In addition, it sheds light onto the genetic features of the pathogen in subject, clarifying facets about its biology, epidemiology, infection mechanisms, and host spectrum, with the future objective to develop specific and efficient control strategies. [ABSTRACT FROM AUTHOR]

Abstract Background Increased contamination of European and Asian wheat and barley crops with “emerging” mycotoxins such as enniatins or beauvericin, produced by Fusarium avenaceum and Fusarium tricinctum, suggest that these phylogenetically close species could be involved in future food-safety crises. Results The mitochondrial genomes of F. tricinctum strain INRA104 and F. avenaceum strain FaLH27 have been annotated. A comparative analysis was carried out then extended to a set of 25 wild strains. Results show that they constitute two distinct species, easily distinguished by their mitochondrial sequences. The mitochondrial genetic variability is mainly located within the intergenic regions. Marks of variations show they have evolved (i) by Single Nucleotide Polymorphisms (SNPs), (ii) by length variations mediated by insertion/deletion sequences (Indels), and (iii) by length mutations generated by DNA sliding events occurring in mononucleotide (A)n or (T)n microsatellite type sequences arranged in a peculiar palindromic organization. The optionality of these palindromes between both species argues for their mobility. The presence of Indels and SNPs in palindrome neighbouring regions suggests their involvement in these observed variations. Moreover, the intraspecific and interspecific variations in the presence/absence of group I introns suggest a high mobility, resulting from several events of gain and loss during short evolution periods. Phylogenetic analyses of intron orthologous sequences suggest that most introns could have originated from lateral transfers from phylogenetically close or distant species belonging to various Ascomycota genera and even to the Basidiomycota fungal division. Conclusions Mitochondrial genome evolution between F. tricinctum and F. avenaceum is mostly driven by two types of mobile genetic elements, implicated in genome polymorphism. The first one is represented by group I introns. Indeed, both genomes harbour optional (inter- or intra-specifically) group I introns, all carrying putatively functional hegs, arguing for a high mobility of these introns during short evolution periods. The gain events were shown to involve, for most of them, lateral transfers between phylogenetically distant species. This study has also revealed a new type of mobile genetic element constituted by a palindromic arrangement of (A) n and (T) n microsatellite sequences whose presence was related to occurrence of SNPs and Indels in the neighbouring regions.

In summer 2019, during a survey on the health status of a hazelnut orchard located in the Tuscia area (the province of Viterbo, Latium, Italy), nuts showing symptoms, such as brown-grayish spots at the bottom of the nuts progressing upward to the apex, and necrotic patches on the bracts and, sometimes, on the petioles, were found and collected for further studies. This syndrome is associated with the nut gray necrosis (NGN), whose main causal agent is Fusarium lateritium. Aiming to increase knowledge about this fungal pathogen, the whole-genome sequencing of a strain isolated from symptomatic hazelnut was performed using long Nanopore reads technology in combination with the higher precision of the Illumina reads, generating a high-quality genome assembly. The following phylogenetic and comparative genomics analysis suggested that this isolate is caused by the F. tricinctum species complex rather than F. lateritium one, as initially hypothesized. Thus, this study demonstrates that different Fusarium species can infect Corylus avellana producing the same symptomatology. In addition, it sheds light onto the genetic features of the pathogen in subject, clarifying facets about its biology, epidemiology, infection mechanisms, and host spectrum, with the future objective to develop specific and efficient control strategies.

Many recent articles feature research on the Fusarium tricinctum species complex (FTSC), and their authors present different ideas on how the isolates of this species complex can be identified at the species level. In previous studies, our aim was to investigate the phylogeny of FTSC strains, which researchers have morphologically identified as Fusarium avenaceum, Fusarium arthrosporioides, and Fusarium anguioides. In the current study, our phylogenetic maximum parsimony and likelihood analyses of the DNA sequences of the translation elongation factor 1-alpha (TEF1) and combined sequences of TEF1 and beta-tubulin (TUB2) supported the existence of at least four main groups among these strains. Main Group I mainly contains F. avenaceum strains, while Main Group II contains two subgroups, one of which primarily includes F. arthrosporioides strains, and the other mainly includes European F. anguioides strains. Main Group III contains strains from different plants that originated from Asia, including two F. anguioides strains. F. avenaceum strains, which are mostly isolated from different trees, form Main Group IV. A fifth group (Main Group V) was only supported by TEF1 sequences. The main groups previously found by us based on TUB2 sequences could be connected to the new species of the FTSC, which were identified based on TEF1 sequences. In addition, we found strains that significantly differ from Main Groups I-V, and we grouped some of them as single, intermediate, or sister groups. All of the main groups of the present work, and some single and intermediate strains, may represent different species of the FTSC, while the two subgroups of Main Group II constitute intraspecific variation. Regardless of whether they belonged to the main groups, all the analysed strains were able to form different enniatins and 2-amino-14,16-dimethyloctadecan-3-ol, but did not produce beauvericin.

Background: Increased contamination of European and Asian wheat and barley crops with "emerging" mycotoxins such as enniatins or beauvericin, produced by Fusarium avenaceum and Fusarium tricinctum, suggest that these phylogenetically close species could be involved in future food-safety crises. Results: The mitochondrial genomes of F. tricinctum strain INRA104 and F. avenaceum strain FaLH27 have been annotated. A comparative analysis was carried out then extended to a set of 25 wild strains. Results show that they constitute two distinct species, easily distinguished by their mitochondrial sequences. The mitochondrial genetic variability is mainly located within the intergenic regions. Marks of variations show they have evolved (i) by Single Nucleotide Polymorphisms (SNPs), (ii) by length variations mediated by insertion/deletion sequences (Indels), and (iii) by length mutations generated by DNA sliding events occurring in mononucleotide (A)n or (T)n microsatellite type sequences arranged in a peculiar palindromic organization. The optionality of these palindromes between both species argues for their mobility. The presence of Indels and SNPs in palindrome neighbouring regions suggests their involvement in these observed variations. Moreover, the intraspecific and interspecific variations in the presence/absence of group I introns suggest a high mobility, resulting from several events of gain and loss during short evolution periods. Phylogenetic analyses of intron orthologous sequences suggest that most introns could have originated from lateral transfers from phylogenetically close or distant species belonging to various Ascomycota genera and even to the Basidiomycota fungal division. Conclusions: Mitochondrial genome evolution between F. tricinctum and F. avenaceum is mostly driven by two types of mobile genetic elements, implicated in genome polymorphism. The first one is represented by group I introns. Indeed, both genomes harbour optional (inter- or intra-specifically) group I introns, all carrying putatively functional hegs, arguing for a high mobility of these introns during short evolution periods. The gain events were shown to involve, for most of them, lateral transfers between phylogenetically distant species. This study has also revealed a new type of mobile genetic element constituted by a palindromic arrangement of (A) n and (T) n microsatellite sequences whose presence was related to occurrence of SNPs and Indels in the neighbouring regions. [ABSTRACT FROM AUTHOR]

The winter annual grass Bromus tectorum (cheatgrass) has become highly invasive in semiarid ecosystems of western North America. In these areas, a natural phenomenon, complete cheatgrass stand failure ('die-off'), is apparently caused by a complex interaction among soilborne fungal pathogens. Several Fusarium strains belonging to the Fusarium tricinctum species complex were isolated from these soils and found to be pathogenic on B. tectorum seeds. One of these strains was produced in cheatgrass seed culture to evaluate its ability to produce phytotoxins. Six metabolites were isolated and identified by spectroscopic methods (essentially 1D and 2D NMR and ESIMS) as acuminatopyrone (1), blumenol A (2), chlamydosporol (3), isochlamydosporol (4), ergosterol (5) and 4-hydroxybenzaldehyde (6). Upon testing against B.tectorum in a seedling bioassay, (6) the coleoptile and radicle length of cheatgrass seedlings were significantly reduced. Compounds 1 and 2 showed moderate activity, while 3–5 were not significantly different from the control. [ABSTRACT FROM AUTHOR]

Worldwide, while Fusarium graminearum is the main causal species of Fusarium head blight (FHB) in small-grain cereals, a diversity of FHB-causing species belonging to different species complexes has been found in most countries. In the U.S., FHB surveys have focused on the Fusarium graminearum species complex (FGSC) and the frequencies of 3-ADON, 15-ADON, and nivalenol (NIV) chemotypes. A large-scale survey was undertaken across the state of North Carolina in 2014 to explore the frequency and distribution of F. graminearum capable of producing NIV, which is not monitored at grain intake points. Symptomatic wheat spikes were sampled from 59 wheat fields in 24 counties located in three agronomic zones typical of several states east of the Appalachian Mountains: Piedmont, Coastal Plain, and Tidewater. Altogether, 2197 isolates were identified to species using DNA sequence-based methods. Surprisingly, although F. graminearum was the majority species detected, species in the Fusarium tricinctum species complex (FTSC) that produce "emerging mycotoxins" were frequent, and even dominant in some fields. The FTSC percentage was 50–100% in four fields, 30–49% in five fields, 20–29% in five fields, and < 20% in the remaining 45 fields. FTSC species were at significantly higher frequency in the Coastal Plain than in the Piedmont or Tidewater (P <.05). Moniliformin concentrations in samples ranged from 0.0 to 38.7 μg g−1. NIV producing isolates were rare statewide (2.2%), and never >12% in a single field, indicating that routine testing for NIV is probably unnecessary. The patchy distribution of FTSC species in wheat crops demonstrated the need to investigate the potential importance of their mycotoxins and the factors that allow them to sometimes outcompete trichothecene producers. An increased sampling intensity of wheat fields led to the unexpected discovery of a minority FHB-causing population. • In the US, little is known about the role of fusarial diversity in FHB epidemics. • A large-scale survey of wheat fields in North Carolina found F. graminearum was the majority species. • However, there were moderate to high frequencies of non-trichothecene producers in some fields. • These strains produced detectable amounts of moniliformin, an "emerging mycotoxin". • The results highlight the value of increasing field sampling intensity. [ABSTRACT FROM AUTHOR]