Carotid artery stenosis: prospective comparison of CT, three-dimensional gadolinium-enhanced MR, and conventional angiography

PURPOSE

To prospectively compare gadolinium-enhanced magnetic resonance (MR) angiography and computed tomographic (CT) angiography with digital subtraction angiography (DSA) for use in detecting atheromatous stenosis and plaque morphology at the carotid bifurcation.

MATERIALS AND METHODS

Forty-four carotid arteries (in 22 patients) were analyzed by using CT angiography, enhanced MR angiography, and DSA. CT and enhanced MR angiograms were reconstructed with maximum intensity projection and multiplanar volume reconstruction. The following four features were analyzed: degree of stenosis on the basis of North American Symptomatic Carotid Endarterectomy Trial criteria, length of stenosis, luminal surface, and presence of ulcers.

RESULTS

There was significant correlation between CT angiography, enhanced MR angiography, and DSA for degree and length of stenosis. With enhanced MR angiography and CT angiography, degree of stenosis was underestimated in two of 44 cases. No case of overestimation with CT angiography was found. Severe internal carotid artery stenoses were detected with high sensitivity and specificity: 100% and 100%, respectively, with CT angiography; 93% and 100%, respectively, with enhanced MR angiography. Luminal surface irregularities were most frequently seen at CT angiography. With CT angiography and enhanced MR angiography, more ulceration was detected than with DSA.

CONCLUSION

There was a significant correlation between CT angiography, enhanced MR angiography, and DSA in evaluation of carotid artery stenosis. Enhanced MR angiography or CT angiography can be used to adequately evaluate carotid stenosis.

Aneurysmal forms of cervical artery dissection : associated factors and outcome

BACKGROUND AND PURPOSE

The natural history of aneurysmal forms of cervical artery dissection (CAD) is ill defined. The aims of this study were to assess (1) clinical and anatomic outcome of aneurysmal forms of extracranial internal carotid artery (ICA) and vertebral artery (VA) dissections and (2) factors associated with aneurysmal forms of CAD.

METHODS

Seventy-one consecutive patients with CAD were reviewed. Aneurysmal forms of CAD were identified from all available angiograms by 2 neuroradiologists. The frequency of arterial risk factors, of multiple vessel dissections, and of artery redundancies was compared in patients with and without aneurysm. Patients with aneurysm were invited by mail to undergo a final clinical and radiological evaluation.

RESULTS

Of the 71 patients, 35 (49.3%) had a total of 42 aneurysms. Thirty aneurysms were located on a symptomatic artery (ICA, 23; VA, 7) and 12 on an asymptomatic artery (ICA, 10; VA, 2). Patients with aneurysm had multiple dissections of cervical vessels (18/35 versus 7/36; P:=0.005) and arterial redundancies (20/35 versus 11/36; P:=0.02) more frequently than patients without aneurysm. They were also more often migrainous (odds ratio=2.7 [95% CI, 0.8 to 8.5]) and tobacco users (odds ratio=2.2 [95% CI, 0.7 to 6.3]). Clinical and anatomic follow-up information was available for 35 (100%) and 33 patients (94%), respectively. During a mean follow-up of >3 years, no patient had signs of cerebral ischemia, local compression, or rupture. At follow-up, 46% of the aneurysms involving symptomatic ICA were unchanged, 36% had disappeared, and 18% had decreased in size. Resolution was more common for VA than for ICA aneurysms (83% versus 36%). None of the aneurysms located on an asymptomatic ICA had disappeared.

CONCLUSIONS

Although aneurysms due to CAD frequently persist, patients carry a very low risk of clinical complications. This favorable clinical outcome should be kept in mind before potential harmful treatment is contemplated.

Motion artifacts of the aorta simulating aortic dissection on spiral CT

PURPOSE

Motion artifacts of the ascending aorta may impair image quality and simulate an intimal flap or a false channel. The purpose of this study is to evaluate the prevalence, amplitude, and extent of motion artifacts of the aorta in spiral CT and to specify the effects of acquisition and reconstruction parameters on these artifacts.

METHOD

One hundred seventy-one thoracic spiral CT examinations were retrospectively analyzed by two reviewers. The analysis sought to determine the presence, location, amplitude, and extent of artifacts of the ascending aorta.

RESULTS

Aortic artifacts were detected on spiral CT in 57% of cases. The mean amplitude and mean extent were 4+/-4 and 6+/-7 mm, respectively. Artifacts in the ascending aorta were significantly higher with the 360 degrees linear interpolation (LI) algorithm than with the 180 degrees LI algorithm.

CONCLUSION

The prevalence of motion artifacts on spiral CT is higher in this study than the reported prevalence in incremental CT. However, this higher prevalence is significantly reduced when the 180 degrees LI algorithm is used.

A glutathione S-transferase cDNA identified by mRNA differential display is upregulated during somatic embryogenesis in Cichorium

CHI-GST1, a cDNA encoding a glutathione S-transferase, was isolated by differential display in leaf tissues of chicory, during the early stages of somatic embryogenesis. Expression analysis of the gene by Northern blot indicated that the transcript accumulation is specific of the leaf developing somatic embryogenesis and is not observed in leaf tissue of the non-embryogenic cultivar.

A nonsymbiotic hemoglobin gene is expressed during somatic embryogenesis in Cichorium

After differential screening of a cDNA library corresponding to genes expressed during the early stages of somatic embryogenesis in leaf tissue from the Cichorium hybrid '474' (C. intybus L., var. sativumxC. endivia L., var. latifolia) a nonsymbiotic hemoglobin cDNA was obtained. Studies of the expression of the gene corresponding to this clone by Northern blot analysis suggest that in Cichorium a nonsymbiotic hemoglobin gene is specifically expressed under somatic embryogenesis-inducing conditions, and that its expression is not related to stress caused by wounding or tissue culture conditions.

Phosphorus supply, arbuscular mycorrhizal fungal species, and plant genotype impact on the protective efficacy of mycorrhizal inoculation against wheat powdery mildew

A potential alternative strategy to chemical control of plant diseases could be the stimulation of plant defense by arbuscular mycorrhizal fungi (AMF). In the present study, the influence of three parameters (phosphorus supply, mycorrhizal inoculation, and wheat cultivar) on AMF protective efficiency against Blumeria graminis f. sp. tritici, responsible for powdery mildew, was investigated under controlled conditions. A 5-fold reduction (P/5) in the level of phosphorus supply commonly recommended for wheat in France improved Funneliformis mosseae colonization and promoted protection against B. graminis f. sp. tritici in a more susceptible wheat cultivar. However, a further decrease in P affected plant growth, even under mycorrhizal conditions. Two commercially available AMF inocula (F. mosseae, Solrize®) and one laboratory inoculum (Rhizophagus irregularis) were tested for mycorrhizal development and protection against B. graminis f. sp. tritici of two moderately susceptible and resistant wheat cultivars at P/5. Mycorrhizal levels were the highest with F. mosseae (38 %), followed by R. irregularis (19 %) and Solrize® (SZE, 8 %). On the other hand, the highest protection level against B. graminis f. sp. tritici was obtained with F. mosseae (74 %), followed by SZE (58 %) and R. irregularis (34 %), suggesting that inoculum type rather than mycorrhizal levels determines the protection level of wheat against B. graminis f. sp. tritici. The mycorrhizal protective effect was associated with a reduction in the number of conidia with haustorium and with an accumulation of polyphenolic compounds at B. graminis f. sp. tritici infection sites. Both the moderately susceptible and the most resistant wheat cultivar were protected against B. graminis f. sp. tritici infection by F. mosseae inoculation at P/5, although the underlying mechanisms appear rather different between the two cultivars. This study emphasizes the importance of taking into account the considered parameters when considering the use of AMF as biocontrol agents.

Are ineffective defence reactions potential target for induced resistance during the compatible wheat-powdery mildew interaction?

Powdery mildew caused by Blumeria graminis f.sp. tritici, an obligate aerial biotrophic fungus, would be one of the most damaging wheat (Triticum aestivum) diseases without the extensive use of conventional fungicides. In our study, the expression levels of some basal defence-related genes were investigated during a compatible interaction in order to evaluate wheat reactions to infection, along with the different stages of the infectious process in planta. As fungal conidia initiated their germination and developed appressorial germ tube (AGT), early defence reactions involved the expression of a lipoxygenase (LOX)- and an oxalate oxidase (OXO)-encoding genes, followed by activations of corresponding LOX (EC 1.13.11.12) and OXO (EC 1.2.3.4) activities, respectively. When penetration of AGT took place, up-regulation of chitinases (CHI) and PR1-encoding genes expression occurred along with an increase of CHI (EC 3.2.1.14) activity. Meanwhile, expression of a phenylalanine ammonia-lyase-encoding gene also took place. Up-regulation of a phospholipase C- and lipid transfer proteins-encoding genes expression occurred during the latest stages of infection. Neither the phi glutathione S-transferase (GST)-encoding gene expression nor the GST (EC 2.5.1.13) activity was modified upon wheat infection by powdery mildew. Whether these defence reactions during such a compatible interaction are markers of immunity or susceptibility, and whether they have the ability to contribute to protection upon modulation of their timing and their intensity by resistance inducers are discussed.

Correlation of cytological and biochemical parameters with resistance and tolerance to Mycosphaerella graminicola in wheat

This study investigated the infection process of Mycosphaerella graminicola and enzyme activities related to reactive oxygen species (ROS) or oxylipin biosynthesis in four French wheat cultivars with variable resistance to M. graminicola infection. At field level, cultivars Caphorn, Maxyl and Gen11 were susceptible, whereas Capnor showed high levels of quantitative resistance. Moreover, Capnor and Gen11 were tolerant, i.e., their yield was less affected by infection compared to non-tolerant Maxyl and Caphorn. These four cultivars were inoculated under laboratory conditions with the M. graminicola IPO323 reference strain. Cytological and biochemical responses were studied on collected first plantlet leaves and several features discriminated between cultivars. However, resistance and tolerance had no impact on the fungal infection process. Levels of lipoxygenase (LOX), peroxidase (PO) and glutathione-S-transferase (GST) activities were also compared with regard to cultivar resistance or tolerance to M. graminicola. LOX, PO and GST activities did not discriminate resistance and tolerance profiles, although a low level of PO in inoculated and non-inoculated plants could be associated with tolerance. In addition, cell necrosis correlated positively with LOX in non-tolerant cultivars, while mycelia surrounding stomata were positively correlated with PO in the resistant cultivar. GST activity presented correlations between cytological and biochemical parameters only for susceptible cultivars. Stomatal and direct penetration were positively correlated with GST activity in the susceptible non-tolerant cultivars, while these correlations were negative in the tolerant cultivar. When combining cytological and biochemical observations with resistance and tolerance profiles, for each cultivar and at each time point, cultivars could be classified in tight accordance with their previous field characterisation. Moreover, tolerance allowed us to distinguish susceptible cultivars when both biochemical and cytological parameters were considered together.

Intracranial aneurysm on CTA: demonstration using a transparency volume-rendering technique

We report an interesting transparency study using a volume-rendering technique applied to CT angiography in a patient with a sylvian aneurysm. On a single view, all the information required for the aneurysmal treatment could be analyzed. Comparison with maximum intensity projection and virtual endoscopy reconstructions was performed.

A Plant Nutrient- and Microbial Protein-Based Resistance Inducer Elicits Wheat Cultivar-Dependent Resistance Against Zymoseptoria tritici

The induction of plant defense mechanisms by resistance inducers is an attractive and innovative alternative to reduce the use of fungicides on wheat against Zymoseptoria tritici, the responsible agent of Septoria tritici blotch (STB). Under controlled conditions, we investigated the resistance induction in three wheat cultivars with different susceptible levels to STB as a response to a treatment with a sulfur, manganese sulfate, and protein-based resistance inducer (NECTAR Céréales). While no direct antigermination effect of the product was observed in planta, more than 50% reduction of both symptoms and sporulation were recorded on the three tested cultivars. However, an impact of the wheat genotype on resistance induction was highlighted, which affects host penetration, cell colonization, and the production of cell-wall degrading enzymes by the fungus. Moreover, in the most susceptible cultivar Alixan, the product upregulated POX2, PAL, PR1, and GLUC gene expression in both noninoculated and inoculated plants and CHIT2 in noninoculated plants only. In contrast, defense responses induced in Altigo, the most resistant cultivar, seem to be more specifically mediated by the phenylpropanoid pathway in noninoculated as well as inoculated plants, since PAL and CHS were most specifically upregulated in this cultivar. In Premio, the moderate resistant cultivar, NECTAR Céréales elicits mainly the octadecanoid pathway, via LOX and AOS induction in noninoculated plants. We concluded that this complex resistance-inducing product protects wheat against Z. tritici by stimulating the cultivar-dependent plant defense mechanisms.

PROTECTION EFFICACY AND MODES OF ACTION OF TWO RESISTANCE INDUCERS ON WHEAT AGAINST SEPTORIA TRITICI BLOTCH

Septoria tritici blotch caused by Mycosphaerella graminicola is one of the most devastating foliar diseases of wheat. Disease control relies heavily on fungicides, but frequent development of fungal resistance and the negative impact of their extensive use on the environment and human health increasingly compromise this control strategy. Plant resistance inducers could be an alternative to conventional fungicides to control in a more durable manner this pathogen. Here, we tested in the greenhouse two resistance inducers (FSOV7 and FSOV10) on two wheat cultivars, Alixan (susceptible) and Altigo (resistant), against M. graminicola. FSOV7 conferred a significant protection level on both cultivars, while FSOV10 conferred a significant protection level on the resistant cv. Altigo only. Furthermore, the modes of action of the two inducers were examined using cytological, biochemical and molecular approaches. In planta, investigation of the infection process showed that FSOV10 significantly reduced fungal spore germination, whereas FSOV7 did not. An association of protection efficacy with a decrease of fungal biomass and fungal β-1, 4-endoxylanase and protease activities was observed in both cultivars. However, no association of plant peroxidase activity with protection efficacy was recorded, whatever the cultivar and the resistance inducer. A RT-qPCR assay revealed significant inductions of the expression of genes involved in different defence pathways; further statistical analyses should determine which genes are associated with the observed protection efficacies. This study showed significant inducer-cultivar interactions on wheat against M. graminicola and allowed us to investigate the modes of action on wheat of the two studied resistance inducers.

Induction of resistance in wheat by bacterial cyclic lipopeptides

Three families of lipopeptides (LPs), surfactin, iturin (including mycosutilin) and fengycin, produced by the rhizabacterium Bacillus subtilis have received considerable attention for their antimicrobial, cytotoxic, antitumor, immunosuppressant and surfactant properties. Among them, iturins and fengycins generally display a strong in vitro antifungal activity. In addition, surfactins are powerful bio surfactants, and although they don't show any direct fungitoxicity, they exhibit some synergistic effect with the antifungal activity of iturins. The aim of our work is to characterize mycosubtilin, surfactin and fengycin, for their ability to protect wheat against two pathogens, Blumeria graminis f.sp. tritici (Bgt), an obligate parasitic fungus responsible for powdery mildew and Mycosphaerella graminicola (Mg), an hemibiotrophic fungus causing Septoria leaf blotch, two of the most important diseases of this crop. In a first step, we measured the protection efficacy of a preventive treatment with LPs against powdery mildew on wheat leaves. At least 41% and 44% protection levels were obtained when surfactin and mycosubtilin, respectively, were sprayed on wheat leaves at doses corresponding to 4g.ha(-1) in the field. We also tested in vitro the impact of LPs on germination of spores. No direct antifungal effect of LPs was observed on Bgt conidia germination, irrespective of the tested concentrations. However, fengycin strongly decreased the germination of Mg conidia and also considerably delayed its growth. Mycasubtilin completely inhibited conidial germination and therefore also its growth while surfactin did not remarkably affect either germination or growth of this fungus. In a second step, RT-qPCR was used to investigate elicitor and priming effects of surfactin and mycosubtilin on the expression levels of defence-related genes. In non-infectious conditions, both surfactin and mycosubtilin induced the expression of two peroxidase encoding genes (POX2, POX381), however, the expression of LOX (lipoxygenase), AOS (allene oxide synthase) genes involved in the octadecanoid pathway, as well as of the pathogenesis-related genes PR1 was only induced by mycosubtilin. In infectious conditions, only surfactin induced the expression of these genes in response to pBgt, mycosubtilin did not exhibit any priming effect. Depending on the targeted pathogen and on the type of LP, these molecules could exhibit direct antifungal effect and/or defence induction, through either elicitation or potentialisation.

MECHANISMS INVOLVED IN MYCORRHIZAL WHEAT PROTECTION AGAINST POWDERY MILDEW

In France, the Ecophyto 2018 national action plan will set out to reduce the use of pesticides by 50% by 2018, if possible. To achieve this goal, the use of arbuscular mycorrhizal (AM) fungi could be a potential alternative method allowing the control of crop diseases. The inoculation by AM fungi has been demonstrated to protect plants against soil-borne pathogens, but little is known about their effectiveness against aerial pathogens, such as the biotrophic fungus Blumeria graminis f.sp. tritici (Bgt) causing wheat (Triticum aestivum) powdery mildew. In the present study, wheat plants were grown in pots, under controlled conditions. Using various phosphorus (P) concentrations, the effectiveness of three AM inocula (Rhizophagus irregularis (Ri), Funneliformis mosseae (Fm)) and Solrize, a mixture of Ri and Fm) in Orvantis wheat cultivar, were tested. After 42 days of culture, mycorrhizal (M) and non-mycorrhizal (NM) wheat plants were infected by Bgt. A satisfactory mycorrhizal rate was obtained with the phosphorus concentration P/5 (P corresponding to the dose used in wheat fields in = 62 mg/L). Our work shows, for the first time, (i) a protective effect of AM inoculation against wheat powdery mildew, reaching up to 73% with Fm inocula, and (ii) its ability to induce a systemic resistance in wheat. Thereafter, we investigated mechanisms involved in this protection. Control plants, M plants, infected plants by Bgt, and M-infected plants were compared at: (i) cytological level, our results revealed that papillae and whole-fluorescent cells presence was induced, conversely fungal haustorium formation in epidermal cells was reduced within M plants leaves (ii) enzymatic level-by assessing defense enzyme activities (lipoxygenase, peroxidase) known as defense markers were measured 24, 48, 72 and 96 hours after infection (hai). The importance of these activities in the defense pathways induced in wheat by AM fungi will be discussed.

ASCORBIC ACID CONTROLS MYCOSPHAERELLA GRAMINICOLA IN BREAD AND DURUM WHEAT THROUGH DIRECT EFFECT ON THE PATHOGEN AND INDIRECT ACTION VIA PLANT DEFENCE

Septoria tritici blotch (STB) caused by Mycosphaerella graminicola is one of the most devastating foliar diseases on wheat. Due to the emergence of fungicide-resistant M. graminicola strains and in an effort to reduce the impact of pesticides on the environment, considerable interest has been devoted to alternative control strategies. The use of natural products, especially through a defense-activating effect on the host, could be considered. Acid ascorbic (AA) is synthesized by plants and most animal cells with antioxidant properties. This study aimed at: (i) assessing the protective effect of an AA-based product on bread (BW) and durum (DW) wheat (Triticum aestivum and T. durum, respectively) susceptible cultivars against M. graminicola and (ii) investigating the mechanisms involved in wheat protection. Therefore, the foliar application of a formulated AA-based product (50 mg L-) on 3-week-old wheat plants reduced the infection level by more than 75% for both BW and DW. In vitro experiments revealed that AA induced a strong inhibition of spore germination (at 50 mg L.(-1)) and hyphal growth (at 16 mg L.(-1)) for both M. graminicola strains, infecting either BW or DW. Used as a preventive foliar spray on wheat leaves, microscopic observations revealed that AA inhibits in planta spore germination, hyphal growth, leaf penetration, substomatal colonization and eventually sporulation. Moreover, AA treatment also decreased fungal protease and cell wall degrading enzyme activities, putative pathogenicity determinants of M. graminicola. In addition to these effects on the fungus, AA induced defence reactions in both BW and DW. Indeed, in non-inoculated context, eliciting effect was observed on (i) stimulation of enzymatic activities such as lipoxygenase, peroxydase and catalase and (ii) transcript accumulation of genes encoding for pathogenesis-related (PR) proteins (chitinase class IV, peroxidase). In inoculated condition, accumulation of H2O2 and phenolic compounds increased at the penetration site in AA-treated leaves. In addition, AA treatment impacted the phenylpropanoid pathway through the induction of phenylalanine ammonia lyase activity. These results show that, in our conditions, AA both presents an antifungal activity and triggers several plant defences in wheat and suggest its use to control M. graminicola on both DW and BW.

[Exploration of the origin of supra-aortic arterial trunk: can MR angiography with gadolinium injection replace digital angiography?]

Ostial stenosis of the craniocervical vessels are frequently associated with carotid stenosis. Consequently, exploration of the aortic arch is necessary prior to carotid endarterectomy. Contrast-enhanced MR angiography (gRMA) could replace digital substraction angiography (DSA). The goal of this work was to evaluate gRMA for the detection of ostial stenosis of the craniocervical vessels. Twenty two patients with carotid stenosis > 50% on sonography examination prospectively underwent gRMA and DSA. We analyzed the overall quality of each gRMA and the degree of ostial stenosis of the craniocervical vessels (innominate, left carotid, subclavian and vertebral arteries). Thirteen gRMA examination was considered as good quality and 8 as adequate for diagnosis. There was significant correlation between gRMA and DSA for degree of stenosis (k = 0.82, p < 0.0001). gRMA tends to overestimate degree of ostial stenosis, especially for vertebral arteries. We conclude that gRMA is a promising tool but cannot yet be used as a stand-alone procedure for the evaluation of ostial stenosis of the craniocervical vessels.

ASSOCIATION BETWEEN SPORULATION AND CELL-WALL DEGRADING ENZYMES IN THE WHEAT PATHOGEN MYCOSPHAERELLA GRAMINICOLA

Mycosphaerella graminicola is a hemibiotrophic fungus that causes Septoria tritici blotch (STB), one of the most serious foliar diseases of wheat. STB can occur with a wide range of disease levels on the host, which depend not only on the pathogenicity of fungal strains, but also on the resistance of host cultivars. Here, we investigated the association between the disease level and fungal cell-wall degrading enzyme and protease activities in three wheat cultivars differing in their resistance levels against M. graminicola. The experiments were carried out in the greenhouse using artificial inoculations with the M. graminicola strain T01193. Disease symptoms scored at 21-day post-inoculation (dpi) were significantly higher on the susceptible and moderately resistant cultivars, Alixan and Premio (48% and 42% of diseased leaf area, respectively), than in the resistant one, Altigo (28% of diseased leaf area). Regarding sporulation, the rate of pycnidial density was significantly higher on Alixan (2.9) compared to Premio and Altigo (1.1 and 1.0, respectively). Further biochemical investigations revealed, by 17 dpi, significant fungal beta-1,4-endoxylanase, beta-1,4-endoglucanase and protease activities, whose amounts increased according to the pycnidial density recorded on the infected leaves. At 21 dpi, the amounts of these activities were significantly higher on Alixan compared to Premio and Altigo (0.36 U/mg, 0.63 U/mg and 2.70 mU/mg total proteins on Alixan, 0.09 U/mg, 0.19 U/mg and 0.72 mU/mg total proteins on Premio and 0.05 U/mg, 0.15 U/mg and 0.52 mU/mg total proteins on Altigo for beta-1,4-endoxylanase, beta-1,4-endoglucanase and protease activities, respectively). These results confirm the importance of CWDE and protease activities in the process of fungal sporulation during the necrotrophic phase of M. graminicola.

PLANT OLIGOSACCHARIDES ENHANCE WHEAT DEFENCE RESPONSE AGAINST SEPTORIA LEAF BLOTCH

Our work provides the first evidence for elicitation and protection effects of preventive treatments with oligosaccharides (20%)-based new formulation (Oligos) against Mycosphaerella graminicola, a major pathogen of bread wheat (BW) and durum wheat (DW). In planta Oligos treatment led to strongly reduced hyphal growth, penetration, mesophyll colonization and fructification. During the necrotrophic phase, Oligos also drastically decreased the production of M. graminicola CWDE activities, such as xylanase and glucanase as well as protease activity in both wheat species, suggesting their correlation with disease severity. Concerning plant defence markers, PR2, Chi 4 precursor-, Per- and LOX-1-encoding genes were up-regulated, while glucanase (GLUC), catalase (CAT) and lipoxygenase (LOX) activities and total phenolic compound (PC) accumulation were induced in both (non-inoculated and inoculated contexts. In inoculated context, a localized accumulation of H2O2 and PC at fungal penetration sites and a specific induction of phenylalanine ammonia-Lyase (PAL) enzymatic activity were observed. Moreover, our experiment exhibited some similarities and differences in both wheat species responses. GLUC and CAT activities and H2O2 accumulation were more responsive in DW leaves, while LOX and PAL activities and PC accumulation occurred earlier and to a stronger extent in BW leaves. The tested Oligos formulation showed an interesting resistance induction activity characterized by a high and stable efficiency whatever the wheat species, suggesting it integration in common control strategies against STB on both DW and BW.

[Intracerebral hematoma associated with reduced apparent diffusion coefficient mimicking acute stroke]

We report the case of a 67 year old patient admitted at our institution for acute onset of left hemiplegia. MRI was done 2 h 30 after symptom onset. Diffusion weighted images showed a hyperintense lesion in the right basal ganglia region with restricted apparent diffusion coefficient (ADC=428. 10(-6) mm(2)/s), a 50% decrease in value compared to the normal left side, consistent with acute ischemia. The lesion was hyperintense and moderately heterogeneous at FLAIR imaging, best seen on echo planar T2W images, with hypointense rim consistent with magnetic susceptibility artifact. The appearance and location of the lesion suggested the possibility of hematoma, which was confirmed at CT. Interpretation of ADC values must be performed in correlation with results at imaging including sequences sensitive to magnetic susceptibility artifacts such as echo planar T2*W and T2W sequences in order to exclude the possibility of underlying hematoma.

CHARACTERIZATION OF A TUNISIAN POPULATION OF MYCOSPHAERELLA GRAMINICOLA USING MITOCHONDRIAL DNA MARKERS

The causal agent of Septoria tritici blotch, Mycosphaerella graminicola, is currently the most frequently reported pathogen on wheat crops worldwide. The populations of this fungus were previously studied in Tunisia using microsatellite markers, but no information is available on the mitochondrial (mt) genetic structure of the fungus in this country. The objective of this study was thus to examine the genetic diversity and population structure of M. graminicola in Tunisia using mtDNA markers. A set 105 monoconidial isolates of the pathogen were sampled in 2012 from four geographical locations in Tunisia (Bizerte, Béja, Kef and Jendouba) and assessed for diversity and polymorphism of three mtDNA sequences (Mg1: 388 bp, Mg2: 570 bp, Mg3: 929 bp) using PCR-RFLP-SSCP. Mg2 and Mg3 were the more polymorphic sequences with 12 and 9 observed alleles, respectively, while Mg1 was the less polymorphic one with only two alleles. Data analyses revealed a moderate mt gene diversity and a low mt haplotype diversity within the population. Further analyses showed a low population differentiation (G(ST) = 0.16) and a moderate gene flow (Nm = 2.61) within the population. Both UPGMA and Bayesian clustering methods confirmed this lack of mt genetic structuration. Our study allowed us to characterize for the first time mt genetic structure of M. graminicola in Tunisia and to report a moderate mt gene diversity, a low mt genotype diversity and a lack of mt genetic structure of the parasite in this country.

[Solitary plasmocytoma of the calvarium]

We report a case of 54 year old patient harboring a solitary painless mass of the calvarium. There was a well-defined biparietal lytic lesion on plain skull radiographics. Computed tomography showed a large hyperdense lesion. This lesion was extraaxial and nearly isointense with gray matter on T1 and T2-weighted MR images, and diffusely enhanced after gadolinium injection. Angiography showed hyperovascularity supplied by middle meningeal and superficial temporal arteries. Imaging study bore some similarities to meningioma. A large extra-axial mass with an important lytic lesion should have led to the diagnosis of plasmocytoma.

Induction of resistance in wheat against powdery mildew by bacterial cyclic lipopeptides

In conventional agricultural practices, fungicides are extensively used to control the development of many fungal plant pathogens. However, the reduction of pesticide applications in the field, which is recommended by authorities and approved by public opinion, may lead to a re-emergence of diseases. Alternative strategies have therefore to be developed in order to control fungal infection; one of them is based on plants natural resistance reinforcement caused by elicitors. Our project aims at characterizing mycosubtilin, surfactin and fengycin, three bacterial cyclic non-ribosomal lipopeptides produced by the rhizobacterium Bacillus subtilis, for their ability to induce resistance in wheat against powdery mildew (Blumeria graminis f.sp. tritici). RT-qPCR approach was used to investigate effect of lipopeptides on expression pattern of defence-related genes, such as PR protein-encoding genes or genes involved in plant defence pathways (reactive oxygen species (ROS) metabolism, lipid peroxidation, phenylpropanoid and octadecanoid pathways) in response to fungus and revealed that expression of LOX and PR1 was strongly induced by surfactin at 24h and 18h after inoculation, respectively. Mycosubtilin seemed to be more efficace to induce expression of OXO and Ltp. Surfactin could also induce expression of chitinase encoding genes but neither surfactin nor mycosubtilin could induce the expression of GSTphi and PAL genes in response to the fungus.

Oligogalacturonides induce resistance in wheat against powdery mildew

Biological activities, priming and protective effects of two oligogalacturonides fractions (OGAs) were assayed during a compatible wheat/Blumeria graminis f. sp. tritici interaction. These fractions were obtained from commercial polygalacturonic acid. They both consisted of oligogalacturonides with polymerisation degrees (DP) ranging from 2 to 25, and one of them was a 30% chemically acetylated fraction. A 5 g x L(-1) solution of each fraction was infiltrated in the first leave of ten-days-old plantlets, and activities of defence-related enzymes were measured 48H post-treatment. Among them, oxalate oxidase and peroxidase activities increased, suggesting an elicitation due to both fractions of oligogalacturonides. Some of the pre-treated plantlets were subsequently submitted to powdery mildew infection. As revealed by 3,3'-diaminobenzidine (DAB) staining, the accumulation of hydrogen peroxide (H2O2) at the penetration site of the fungus increased 21H after inoculation to the same extent in areas of plantlets infiltrated by both fractions. On the other hand, the intensity of fluorescence associated with papillae was higher when plantlets were pre-infiltrated with the acetylated fraction, whereas no difference was observed between control plantlets and those treated with the non-acetylated fraction. Moreover, microscopic assessment of the number of haustoria occurring 40H post-inoculation showed it was only reduced when acetylated fraction was used. Despite different modes of action of these molecules, a similar 45% protective effect occurred in both cases when the oligogalacturonides fractions were sprayed on ten-days-old plantlets.

RELATIONSHIP BETWEEN PATHOGENICITY AND FUNGICIDE TOLERANCE IN THE WHEAT PATHOGEN MYCOSPHAERELLA GRAMINICOLA

Septoria tritici blotch caused by Mycosphaerella graminicola (anamorph: Zymoseptoria tritici) is currently the most devastating disease on wheat crops worldwide, especially in regions with suitable climate conditions such as Western Europe. Pathogen control relies mainly on the use of fungicides and resistant cultivars. However, the durability of chemical and genetic control strategies is increasingly compromised in the field since the fungus frequently develops resistance to fungicides and overcomes host resistance. Here, we assessed the association between pathogenicity and fungicide tolerance in eighteen different M. graminicola strains isolated in 2009 from Northern France. These strains were chosen because they exhibited in preliminary experiments a wide range of in vitro tolerance levels against six demethylation inhibitors (epoxiconazole, cyproconazole, fluquinconazole, propiconazole, prothioconazole and pyrefenox). Inoculation of the Scorpion susceptible wheat cultivar in the greenhouse with these strains revealed a great variability in their pathogenicity levels (disease symptoms ranged from 0 to 66% of leaf area bearing pycnidia). Interestingly, strains with high fungicide tolerance levels caused overall the highest disease symptoms (45% of diseased leaf area on average) when compared to those with low fungicide tolerance levels (22% of diseased leaf area on average), thus confirming the association between pathogenicity level and fungicide tolerance in M. graminicola. The occurrence and selection in the field of fungal genotypes combining both pathogenicity and fungicide resistance should be taken into account in disease management strategies.

Towards a more sustainable agriculture: wheat mycorrhization to protect against powdery mildew

One of the means to reduce the use of pesticides, which are harmful for humans and the environment, is the development of alternative methods to control crop diseases. In this context, arbuscular mycorrhizal inoculation possesses a great potential for crop production by a more sustainable agriculture. Our work aims to (i) determine the optimal conditions for wheat mycorrhization (ii) study the impact of arbuscular mycorrhizal inoculation on a foliar disease of wheat, powdery mildew (Blumeria graminis f.sp. tritici, Bgt), (iii) evaluate the stimulation of natural defences of wheat (Triticuma estivum). Therefore, this work consisted firstly of defining the parameters, affecting the establishment of wheat mycorrhization, such as: phosphorus concentration (62, 12.5, 6.2 mg/L), culture time (4, 5, 6, 7 weeks), arbuscular mycorrhizal species used as an inoculum (Rhizophagus irregularis (Ri), Glomus masseae (Gm) and the mixture of (Ri+Gm)) and wheat cultivars (Orvantis and Lord, sensitive and moderately resistant to Bgt, respectively). Secondly, the protective effect of mycorrhizal inoculation against Bgt was estimated by comparing infection rates of wheat seedlings subjected and non-subjected to AMF. Finally, to better understand the biochemical mechanisms involved in the protection, two enzymatic activities described as defense markers [lipoxygenase (LOX) and peroxidase (POX)] were also assessed. Extensive mycorrhization (about 31%) was obtained at P/5 concentration (12.5 mg/L) when wheat plants were 6 weeks old. The highest colonization rate was obtained when wheat was inoculated with Gm compared to SZE and Ri. The higher resistance level of Lord wheat cultivar against Bgt did not affect the mycorrhizal rate compared to the more susceptible cultivar Orvantis. Our work showed a significant protection level in mycorrhizal (M) wheat plants against Bgt, estimated to about 25 and 43% with Ri and SZE respectively compared to non-mycorrhizal (NM) Orvantis plants. The protection levels percent's were about 30 and 64% for Lord plants. The protection was higher for Lord than Orvantis and seems to depend on the resistance degree. These results suggest the induction of a systemic resistance by mycorrhizal inoculation. Our results showed an increase of both activities (LOX and POX) in wheat infected by Bgt for both (M) and (NM) plants by the inoculum SZE (Ri+Gm) at P/5 phosphorus concentration.