Polyphasic approach used for distinguishing Fusarium temperatum from Fusarium subglutinans

Morphological, biological, and phylogenetic approaches were undertaken for the identification of pathogenic species F. temperatum in the Serbian population of F. subglutinans collected in the 1999-2010 period from Zea mays (3 root, 15 stalk, and 6 seed samples), Sorghum bicolor (two seed samples), Hordeum vulgare (one seed sample) and Taraxacum officinale (one seed sample). Based on interspecies mating compatibility analyses and the maximum parsimony analysis of EF-1α sequences, only two strains, originating from S. bicolor seed (MRIZP 0418 and MRIZP 0552), were identified as F. temperatum, while the remaining 26 single-spore strains were identified as F. subglutinans Group 2. In situ detached barley leaf assay and artificially stalk and ear inoculation of two maize hybrids demonstrated that both F. temperatum and F. subglutinans strains were medium and strong pathogens under laboratory and field conditions, respectively. These are the first data on the F. temperatum as seed-borne pathogens of sorghum, as well as pathogenicity of F. temperatum strains on maize

Le monument funéraire néolithique de Poses « Sur la Mare » (Eure)

La fouille d’une large surface, à Poses, au lieu-dit « Sur la Mare », a permis d’étudier les vestiges d’une petite structure funéraire en partie arasée. Cet édifice est constitué d’une couronne d’empierrement en blocs de craie, de forme ovalaire et délimitant un espace central quadrangulaire d’environ 4 m sur 6. Cet espace intérieur, légèrement excavé, a fourni d’une part une structure contenant un vase, et d’autre part une nappe d’ossements brûlés associés à d’autres restes également brûlés : fragments de céramique, outillages osseux et lithique. Les questions concernant le type de fonctionnement, l’architecture et la datation de cet édifice à une phase de transition entre les Néolithiques moyen et récent font ici l’objet d’une discussion.Area excavation at Poses “Sur la Mare” revealed a small Neolithic burial structure. This partly eroded monument consisted of an oval surround of chalk blocks, defining a central quadrangular area 4 by 6 metres. This space, slightly hollowed, had in one section a feature containing a pot, in another section a deposit of cremated bones associated with other burnt material: shards, worked bone and flints. Discussion centres on the function, the architecture and the dating of this structure in a transitional phase between the middle and late Neolithic

Genetic divergence and chemotype diversity in the fusarium head blight pathogen Fusarium poae

Fusarium head blight is a disease caused by a complex of Fusarium species. F. poae is omnipresent throughout Europe in spite of its low virulence. In this study, we assessed a geographically diverse collection of F. poae isolates for its genetic diversity using AFLP (Amplified Fragment Length Polymorphism). Furthermore, studying the mating type locus and chromosomal insertions, we identified hallmarks of both sexual recombination and clonal spread of successful genotypes in the population. Despite the large genetic variation found, all F. poae isolates possess the nivalenol chemotype based on Tri7 sequence analysis. Nevertheless, Tri gene clusters showed two layers of genetic variability. Firstly, the Tri1 locus was highly variable with mostly synonymous mutations and mutations in introns pointing to a strong purifying selection pressure. Secondly, in a subset of isolates, the main trichothecene gene cluster was invaded by a transposable element between Tri5 and Tri6. To investigate the impact of these variations on the phenotypic chemotype, mycotoxin production was assessed on artificial medium. Complex blends of type A and type B trichothecenes were produced but neither genetic variability in the Tri genes nor variability in the genome or geography accounted for the divergence in trichothecene production. In view of its complex chemotype, it will be of utmost interest to uncover the role of trichothecenes in virulence, spread and survival of F. poae

A European Database of Fusarium graminearum and F. culmorum Trichothecene Genotypes

. Fusarium species, particularly Fusarium graminearum and F culmorum, are the main cause of trichothecene type B contamination in cereals. Data on the distribution of Fusarium trichothecene genotypes in cereals in Europe are scattered in time and space. Furthermore, a common core set of related variables (sampling method, host cultivar, previous crop, etc.) that would allow more effective analysis of factors influencing the spatial and temporal population distribution, is lacking. Consequently, based on the available data, it is difficult to identify factors influencing chemotype distribution and spread at the European level. Here we describe the results of a collaborative integrated work which aims (1) to characterize the trichothecene genotypes of strains from three Fusarium species, collected over the period 2000-2013 and (2) to enhance the standardization of epidemiological data collection. Information on host plant, country of origin, sampling location, year of sampling and previous crop of 1147 F graminearurn, 479 F culmorum, and 3 F cortaderiae strains obtained from 17 European countries was compiled and a map of trichothecene type B genotype distribution was plotted for each species. All information on the strains was collected in a freely accessible and updatable database (www.catalogueeu.luxmcc.lu), which will serve as a starting point for epidemiological analysis of potential spatial and temporal trichothecene genotype shifts in Europe. The analysis of the currently available European dataset showed that in F. grarninearum, the predominant genotype was 15-acetyldeoxynivalenol (15-ADON) (82.9%), followed by 3-acetyldeoxynivalenol (3-ADON) (13.6%), and nivalenol (NIV) (3.5%). In F culmorum, the prevalent genotype was 3-ADON (59.9%), while the NIV genotype accounted for the remaining 40.1%. Both, geographical and temporal patterns of trichothecene genotypes distribution were identified.</p

Diversity of Colletotrichum species from wild Stylosanthes, a challenge for anthracnose management of cultivated Stylosanthes

Doctorat en sciences agronomiques et ingénierie biologique - UCL, 199

Molecular strategy for identification in Aspergillus section Flavi.

Aspergillus flavus is one of the most common contaminants that produces aflatoxins in foodstuffs. It is also a human allergen and a pathogen of animals and plants. Aspergillus flavus is included in the Aspergillus section Flavi that comprises 11 closely related species producing different profiles of secondary metabolites. A six-step strategy has been developed that allows identification of nine of the 11 species. First, three real-time PCR reactions allowed us to discriminate four groups within the section: (1) A. flavus/Aspergillus oryzae/Aspergillus minisclerotigenes/Aspergillus parvisclerotigenus; (2) Aspergillus parasiticus/Aspergillus sojae/Aspergillus arachidicola; (3) Aspergillus tamarii/Aspergillus bombycis/Aspergillus pseudotamarii; and (4) Aspergillus nomius. Secondly, random amplification of polymorphic DNA (RAPD) amplifications or SmaI digestion allowed us to differentiate (1) A. flavus, A. oryzae and A. minisclerotigenes; (2) A. parasiticus, A. sojae and A. arachidicola; (3) A. tamarii, A. bombycis and A. pseudotamarii. Among the 11 species, only A. parvisclerotigenus cannot be differentiated from A. flavus. Using the results of real-time PCR, RAPD and SmaI digestion, a decision-making tree was drawn up to identify nine of the 11 species of section Flavi. In contrast to conventional morphological methods, which are often time-consuming, the molecular strategy proposed here is based mainly on real-time PCR, which is rapid and requires minimal handling

Conidium germination and appressorium penetration of Colletotrichum gloeosporioides on Stylosanthes guianensis

Pre-penetration and early penetration phases of two pathogenic strains of Colletotrichum gloeosporioides (HM 502, HM 514)from Zaire were investigated quantitatively on four Stylosanthes guianensis genotypes (cv. Schofield, cv. Graham, CIAT 184 and CIAT 10136) of various levels of susceptibility. The results demonstrated control of the rates and type of conidial germination by the fungus, influenced to a lesser extent by the host genotype. Cell reactions were visible as papillae and cytoplasmic aggregations closely associated with the penetration peg. No fungal growth was observed when deposits of papillae occurred under appressoria-forming infection pegs, whereas the effect of the cytoplasmic aggregations varied according to the host genotype. In the interactions with strain HM 502, the highest rates of plant reaction were recorded on the resistant CIAT 184 genotype, while the highest level of penetration without reaction was observed on the most susceptible cv. Schofield. Cytoplasmic aggregations were also observed under a few ungerminated appressoria on this genotype. Differences were thus detected in the rates and types of conidial germination, in the rates and types of cell reactions under appressoria and in the appressorial penetration rates without cell reactions. However, these differences did not completely explain the range of macroscopic symptoms observed on the various genotypes