Spread Of Fungus Research Articles

Transformation ofFusarium virguliforme,the Causal Agent of Sudden Death Syndrome of Soybean

Fusarium virguliforme is a soil-borne pathogen that causes sudden death syndrome (SDS) in soybean. SDS is an important disease that causes significant losses in soybean growing areas worldwide. Little is known about the interaction between F. virguliforme and soybean. We have developed a protoplast-based fungal transformation system for F. virguliforme. One of the applications of the transformation system was the production of a green fluorescent protein (GFP)-expressing fungal transformant. The GFP-expressing fungus can be used to study fungal infection processes including fungal penetration, colonization, and spread, especially at the early stages of disease development. Furthermore, in an attempt to increase the genetic resources available to identify and characterize fungal virulence genes involved in the F. virguliforme-soybean system, we generated random insertional mutations in F. virguliforme using restriction enzyme mediated integration.

Impact of Verticillium longisporum on Yield and Morphology of Winter Oilseed Rape (Brassica napus) in Relation to Systemic Spread in the Plant

AbstractThe impact of Verticillium longisporum on single plant and whole plot yield of oilseed rape (OSR) was studied in field experiments with natural infection or artificial soil infestation. Disease incidence (DI) and disease severity (DS) correlated with the amount of inoculum provided at four different levels by addition of infested rapeseed straw to the soil. DI and DS were higher in 2003, a year with higher average soil and air temperatures, than in 2004, at similar levels of added inoculum. Maximum DI and DS levels achieved with artificial soil infestation were 54.3% and 0.57 (rating scale from 0 to 2), respectively, which was insufficient to induce significant yield reduction in whole plots. In contrast, a significant decrease in yield was recorded on single naturally infected plants removed from the field at growth stage (GS) 83 to 85. Yield losses of single plants accounted for 20 to more than 80% at DS levels above 5 (scale 0 to 9). The systemic spread of V. longisporum was significantly delayed in plants in the field with substantial colonization of the shoots not occurring before maturity stages. However, fungal systemic spread into the shoots was faster in 2003, consistent with the visual disease assessment in the field. Conversely, the pathogen systemically spread after 28 days in plants (susceptible cultivar ‘Falcon’) in the greenhouse. Root dip inoculation with conidia suspension induced earlier and more severe disease symptoms than microsclerotia added to the soil. In contrast to the field, intense stunting was recorded on inoculated plants in the greenhouse. The susceptible cultivar, ‘Falcon’, showed higher DS, stronger reduction in root and shoot lengths and a faster fungal spread in the plant tissue than the moderate susceptible cultivar, ‘Talent’. Climatic conditions appear to be responsible for the strong delay in fungal invasion of plants in the field. This may prevent the plants from stunting and mitigate the overall yield effects of the disease. This study indicates a significant yield damage potential of V. longisporum in areas with DI above 60% and conditions accelerating the systemic pathogen spread in the plants.

A Ten-Year Study of the Effectiveness of an Educative Programme in Ensuring the Ecological Sustainability of Recreational Activities in the Brisbane Ranges National Park, South-Eastern Australia

Managing the spread of cinnamon fungus, an exotic root-rotting pathogen which kills a wide range of native plants, is an over-riding management concern in the Brisbane Ranges National Park of south-eastern Australia. Parks Victoria has implemented a suite of approaches for informing recreational users about the disease and its ecological impacts. To assess longitudinal changes in the effectiveness of the educative programme, recreational users were surveyed in 1993 and in 2003. 81% were not aware of cinnamon fungus dieback in 1993; the proportion in 2003 was almost unchanged at 83%. Despite the lack of awareness of cinnamon fungus dieback, a large majority (76% in 1993; 74% in 2003) of respondents replied that they had viewed information boards in the park or read visitor guides with information on the disease and its ecological impacts. When recreational users were informed of the impact of infection, there was unanimous support for track closures for quarantine purposes. Our findings indicate that current methods of educating recreational users about cinnamon fungus dieback are not effective. Recommendations are made to improve the penetration of the educational and interpretive information, including the incorporation of affective and cognitive approaches.

Complement induction and complement evasion in patients with cerebral aspergillosis

Cerebral aspergillosis is a mostly lethal infection of the central nervous system. Former results identified low cerebral complement levels as one cause for insufficient immune reaction. Therefore we studied cerebral complement expression after fungal invasion and investigated putative mechanisms of Aspergillus spp to cope with the complement-induced selection pressure. Brain tissue derived from patients with cerebral aspergillosis or non-infected individuals was analyzed immunohistochemically for complement synthesis. Correlations between expression levels were determined statistically. Increased complement synthesis, a prerequisite for strengthened antifungal potency, was visible in resident astrocytes, neurons, oligodendrocytes as well as in infiltrating macrophages after fungal infection. Surprisingly, microglia, although regarded as major immune cells, only marginally participated in synthesis of most complement proteins. Several evasion mechanisms were found that help the fungus to establish a cerebral infection even in the presence of complement: Fungal hyphae limit the surface deposition of C3 and thus interfere with complement-dependent phagocytosis. Furthermore, the “sealing off” in brain abscesses not only inhibits fungal spreading but also forms protection shields against complement attack. Complement indeed seems to represent an important selection pressure and evokes the development of fungal evasion mechanisms. Counteractions for these evasion processes might represent interesting therapeutic approaches.

Phenolic acids composition of maize kernels modulates in planta fungal growth and Trichothecenes B production byF. graminearum?

Kinetics of fungal spread and Trichothecenes B (TCT B) contamination were achieved using four hybrids of Maize characterized by different levels of resistance. Inoculation was performed using a toxigenic Fusarium graminearum strain 5 days after flowering into the silk channel. In addition, phenolic acids composition was evaluated at the different grain filling stages for the four hybrids. Results are discussed with regards to a potential involvement of phenolic acids in limitation of toxins accumulation and resistance level.

Altered expression of the costimulatory molecules CD80, CD86, CD152, PD-1 and ICOS on T-cells from paracoccidioidomycosis patients: Lack of correlation with T-cell hyporesponsiveness

T-cell proliferative hyporesponsiveness, a hallmark of paracoccidioidomycosis immune responses, underlies host’s failure in controlling fungus spread, being reversible with antifungal treatment. The mechanisms leading to this hypoproliferation are not well known. Since costimulatory molecules have been shown to profoundly regulate T-cell immune responses, we investigated the hypothesis that the determinants of the responder versus tolerant state may be the regulated expression of, or signaling by, costimulatory molecules. Expression of CD80, CD86, CD28, CD152, ICOS and PD-1 costimulatory molecules were examined on T-cells and monocytes harvested from stimulated and unstimulated PBMC cultures of active paracoccidioidomycosis patients and healthy individuals cured of past paracoccidioidomycosis. Stimuli were gp43, the immunodominant component of Paracoccidioides brasiliensis, and a Candida antigen. While CD28 expression, critical for optimal T-cell activation, was comparable between patients and controls, CD152, PD-1 and ICOS, which preferentially deliver negative signaling, were overexpressed on patients’ stimulated and unstimulated T-cells. PBMC cultures were carried out in presence of the respective blocking antibodies which, however, failed to restore T-cell proliferation. CD80 and CD86 were equally expressed on patients’ and controls’ monocytes, but overexpressed on patients’ T-cells. Blockade with the respective blocking antibodies on day 4 of the culture also did not restore T-cell proliferation, while, on day 0, differentially inhibited Candida and gp43 responses, suggesting that different antigens require different costimulatory pathways for antigen presentation. Our data favors the hypothesis, raised from other foreign antigen models, that prolonged in vivo antigen exposure leads to an adaptive tolerance T-cell state which is hardly reverted in vitro.

Components of the gene network associated with genotype-dependent response of wheat to the Fusarium mycotoxin deoxynivalenol

The Fusarium mycotoxin deoxynivalenol (DON) facilitates fungal spread within wheat tissue and the development of Fusarium head blight disease. The ability of wheat spikelets to resist DON-induced bleaching is genotype-dependent. In wheat cultivar (cv.) CM82036 DON resistance is associated with a quantitative trait locus, Fhb1, located on the short arm of chromosome 3B. Gene expression profiling (microarray and real-time RT-PCR analyses) of DON-treated spikelets of progeny derived from a cross between cv. CM82036 and the DON-susceptible cv. Remus discriminated ten toxin-responsive transcripts associated with the inheritance of DON resistance and Fhb1. These genes do not exclusively map to Fhb1. Based on the putative function of the ten Fhb1-associated transcripts, we discuss how cascades involving classical metabolite biotransformation and sequestration processes, alleviation of oxidative stress and promotion of cell survival might contribute to the host response and defence against DON.

Native Valve Aspergillus Endocarditis Complicating Lung Transplantation

We present 2 cases of Aspergillus endocarditis occurring in lung transplant recipients, both of whom were treated with early surgical intervention and triazole anti-fungal agents. Neither had evidence of airway colonization/infection with Aspergillus post-transplant, suggesting hematogenous spread of fungi at the time of surgery as a possible mechanism of infection. One case was successfully treated and discharged from the hospital, but, despite initial recovery, death occurred 10 months later due to a recurrence of Aspergillus endocarditis. Aspergillus endocarditis should be considered a relapsing disease and survivors of the condition should receive ongoing anti-fungal therapy.

Alien fungal species distribution: the study case of Favolaschia calocera

Invasive organisms (especially plants and animal species) are considered to be one of the main causes of global biodiversity loss. Up to now, few papers have dealt with the spreading of fungi. The establishment of the geographic origin of alien organisms could be useful to assess their impact on the environment. Favolaschia calocera is a basidiomycete species which was first described from Madagascar, and successively observed in New Zealand in 1969, where it has currently been recorded in more than 200 stands. It has recently also been reported in Australia, Thailand, China, Kenya, and Reunion Island. F. calocera was found in Genoa, Italy, in 1999: this recording represented the first in Europe. Till now, Favolaschia specimens have been collected in six areas around Genoa. F. calocera was observed growing on debris of various vascular plant species (Pteridophytes, Conifers, Mono- and Dicotyledons), thus showing to be a polyphagous species. Because it is spreading, it needs to be monitored. The main goal of our research is to investigate, through molecular phylogeographic analysis, the origin of the Italian strains. The sequencing of the ribosomal DNA ITS region of the Italian specimens followed by Neighbour-joining analysis showed that they cluster with the specimens from New Zealand, Kenya, Norfolk Island and Reunion Island. Hypotheses on the origin and introduction way as well as on its mechanisms of spreading are provided.

A fungal growth model fitted to carbon‐limited dynamics of Rhizoctonia solani

Here, a quasi-steady-state approximation was used to simplify a mathematical model for fungal growth in carbon-limiting systems, and this was fitted to growth dynamics of the soil-borne plant pathogen and saprotroph Rhizoctonia solani. The model identified a criterion for invasion into carbon-limited environments with two characteristics driving fungal growth, namely the carbon decomposition rate and a measure of carbon use efficiency. The dynamics of fungal spread through a population of sites with either low (0.0074 mg) or high (0.016 mg) carbon content were well described by the simplified model with faster colonization for the carbon-rich environment. Rhizoctonia solani responded to a lower carbon availability by increasing the carbon use efficiency and the carbon decomposition rate following colonization. The results are discussed in relation to fungal invasion thresholds in terms of carbon nutrition.

The Occurrence of Pathogenic Fungi During Flax Growing Season in Central Lithuania

Experiments designed to study the variation of diversity of pathogenic fungi occurring in fibre flax agrocenosis during the growing season were conducted at the Lithuanian Institute of Agri- culture Upytė Experimental Station during 1999-2002. The Upytė Experimental Station is situated in Central Lithuania. Phytopathological analyses of seed, soil and plants were done at the laboratory of the Upytė Experimental Station as well as at the Biodestructor Research Laboratory of the Institute of Botany. There were identified in the rhizosphere 9 fungal species belonging to 9 genera. On flax seedlings were identified fungi belonging to 13 genera. On flax leaves at green maturity stage was identified only Oidium lini. On flax stems at green maturity stage were identified fungi belonging to 12 genera. On mature flax stems were found fungi belonging to 15 genera. On flax seed during the experimental years were identified fungi belonging to 16 genera. The number of fungi identified on seeds varied each year, depending on the year's weather conditions during the seed ripening period. Having summarised the results, we can assert that pathogenic fungi Fusarium spp. and Colletotrichum lini, were found both on seed and plant vegetative parts during the whole assessment period. Species composition of fungi present on seed differed depending on the weather conditions. A larger number and more diverse species were found on the seed that ripened during the years with wet growing sea- sons (2000 and 2001) whereas the seed that ripened during dry growing seasons (1999 and 2002) was less infected with fungi. The spread of fungi on stems and leaves was also determined by the weather conditions. Many species of fungi were identified in 2001, when flax crops were lodged; stems and capsules were damaged by hail, and in 2000, when there was much rainfall.

Vascular-Streak Dieback: A New Encounter Disease of Cacao in Papua New Guinea and Southeast Asia Caused by the Obligate Basidiomycete Oncobasidium theobromae

ABSTRACT The basidiomycete Oncobasidium theobromae was identified as the cause of a devastating disease of cacao named vascular-streak dieback (VSD) in Papua New Guinea in the 1960s. VSD now causes losses among cacao seedlings and kills branches in mature cacao trees throughout Southeast Asia and parts of Melanesia. The characteristic symptoms include a green-spotted chlorosis and fall of leaves beginning on the second or third flush behind the stem apex, raised lenticels, and darkening of vascular traces at the leaf scars and infected xylem. Eventually complete defoliation occurs and, if the fungus spreads to the trunk, the tree will die. O. theobromae is a highly specialized, near-obligate parasite of cocoa. It is a windborne, leaf-penetrating, vascular pathogen, and may have evolved as an endophyte on an as yet unidentified indigenous host. The rate of disease spread on cocoa is limited because basidiocarps develop only on fresh leaf scars during wet weather, and basidiospores remain viable for a few hours on the night they are shed. Consequently, very few new infections occur beyond 80-m from diseased trees. Transmission of the disease through seed or infected cuttings has not been demonstrated. Strict quarantine measures applied to the movement of intact plants are crucial in reducing spread of the disease. Integrated management, including the planting of less susceptible genotypes, nursery construction and management, canopy pruning and shade management, provides effective control.

Compatible and Incompatible Interactions in Wheat Involving the Bt-10 Gene for Resistance to Tilletia tritici, the Common Bunt Pathogen

ABSTRACT The infection of wheat lines Neepawa (susceptible), and its sib BW553 that is nearly isogenic for the Bt-10 resistance gene by differentially virulent races T1 and T27 of common bunt (Tilletia tritici), was followed for 21 days following seeding (dfs) using fluorescence and confocal microscopy. Spore germination was nonsynchronous and all spore stages including germination were observed 5 to 21 dfs. Initial host perception of pathogen invasion, based on autofluorescence in epidermal cells adjacent to the appressoria, was similar in both compatible and incompatible interactions, and occurred as early as 5 to 6 dfs. The total number of sites on a 1-cm segment of coleoptile adjacent to the seed that exhibited autofluorescence was similar in both the compatible and incompatible interactions and rose to a maximum of 35 to 40 per 1 cm length of coleoptile following 17 dfs, although new infection events were observed as late as 21 dfs. In the compatible interaction, the autofluorescence became more diffuse 10 to 12 dfs, emanating in all directions in association with fungal spread. In the incompatible interaction, autofluorescence remained restricted to a small area surrounding the penetration site. Two different reaction zones that extended further in tissues surrounding the penetration point in the incompatible interaction compared with the compatible interaction were identified. The accumulation of callose around invading fungal hyphae was observed during both the compatible and incompatible interactions from 8 to 21 dfs. While callose accumulation was more extensive and widespread in the incompatible interaction, it was clearly present in compatible interactions, particularly in treatments involving BW553. These results were confirmed by expression of callose synthase transcripts that were more abundant in BW553 than in Neepawa and were upregulated during pathogen infection in both compatible and incompatible interactions.

Cytological and immunocytochemical studies on responses of wheat spikes of the resistant Chinese cv. Sumai 3 and the susceptible cv. Xiaoyan 22 to infection by Fusarium graminearum

Fusarium head blight (FHB), predominantly caused by Fusarium graminearum and F. culmorum, is one of the most destructive diseases of wheat, reducing grain yield and quality of kernels. In diseased kernels trichothecne mycotoxins accumulate, which are harmful to human and animal health. Pathogen development and host responses to infection by F. graminearum were investigated in wheat spikes of the resistant cv. Sumai 3 and susceptible cv. Xiaoyan 22 to infection by means of electron microscopy and immunogold labelling techniques. The infection process of the pathogen in wheat spikes was similar in both the resistant and susceptible cultivars, but the pathogen developed more slowly in the resistant cv. Sumai 3 compared to the susceptible cv. Xiaoyan 22, indicating that fungal spread was restricted to the spike tissues of the resistant cultivar. The formation of thick-layered appositions and papillae was essentially more pronounced in the infected host tissues of the resistant cultivar than in the susceptible one. s-1,3-glucan was detected in the appositions and papillae. Immunogold labelling studies demonstrated that labelling densities for lignin, thionins and hydroxyproline-rich glycoproteins (HRGP) over the cell walls of the infected tissues of the susceptible wheat cv. Xiaoyan 22 only slightly increased whereas these compounds intensely accumulated in the host cell walls of the infected wheat spikes of the resistant cv. Sumai 3. The labelling densities for the two plant hydrolases, s -1,3-glucanase and chitinase, increased slightly in the infected wheat spike tissues of the susceptible cv. Xiaoyan 22, whereas higher labelling densities of both enzymes were found in the infected wheat spikes from the resistant cv. Sumai 3. Immunogold labelling of the Fusarium toxin DON in the infected wheat spike tissues showed that labelling densities in spike tissues for DON in the resistant cv. Sumai 3 were significantly lower than those in the susceptible cv. Xiaoyan 22. The significance of the induced morphological (e.g. thick-layered wall appositions and papillae) and chemical defence constituents (e.g. s -1,3-glucanase, chitinase, lignin, thionin and HRGP) in resistance to FHB as well as the possible role of DON as an aggressiveness factor in translation of transcripts of defence response genes and spreading of F. graminearum and F. culmorum are discussed.

QTL analysis of resistance to Fusarium head blight in the novel wheat germplasm CJ 9306. I. Resistance to fungal spread

Fusarium head blight (FHB or scab) caused by Fusarium species is a destructive disease in wheat and barley worldwide. The objectives of our study were to identify quantitative trait loci (QTLs) for resistance to FHB spread (Type II resistance) and to quantify the magnitude of their effects in a novel highly resistant wheat germplasm, CJ 9306. A set of 152 F(7) recombinant inbred lines (RILs) derived from a cross Veery/CJ 9306 and two parents were evaluated for FHB resistance by single-floret inoculation in three greenhouse experiments in 2002 and 2004. Percentage (PSS) and number (NSS) of scabby spikelets at 25 days post-inoculation were analyzed. In total 682 simple sequence repeat (SSR) markers were screened for polymorphism between the two parents, and a genetic linkage map was constructed with 208 polymorphic markers. Ten QTLs associated with FHB resistance were detected, five from CJ 9306 and five from Veery. The major QTL on 3BS (QFhs.ndsu-3BS) was validated in CJ 9306, exhibiting greatest additive effects and explained 30.7% of phenotypic variation for PSS on the overall average of three experiments. Another major QTL on 2DL (QFhs.nau-2DL) from CJ 9306 explained 9.9-28.4% of phenotypic variation, with a significant QTL x environment interaction. QFhs.nau-1AS and QFhs.nau-7BS showed lower additive effects and explained lower variance (4.5-9.5%). A QTL on 5AS, decreasing PSS by 10.3% on average, was validated by simple marker analysis and joint trait/experiment IM/CIM analysis despite insignificance for single-experiment IM and CIM analyses. Likewise, QFhs.nau-2BL and QFhs.nau-1BC from Veery could reduce PSS by 13.2 and 11.4%, respectively. The effects of other three minor QTLs from Veery were significant for one experiment and combined analysis. Comparisons of two- and three-locus combinations suggested that the effects of FHB resistance QTLs/genes could be accumulated, and the resistance could be feasibly enhanced by selection of favorable alleles for multiple loci. Four two-locus combinations and two three-locus combinations were suggested as the preferential choices in practical marker-assisted selection program.

Fungi Isolated from Integument and Guts of <I>Coptotermes formosanus</I> and Their Antagonistic Effect on <I>Gleophyllum trabeum</I>

In our earlier efforts to demonstrate the spread of a brown rot fungus, Gloeophyllum trabeum (Pers.) Murrill by Formosan subterranean termites, Coptotermes formosanus Shiraki, we found not only that C. formosanus does not spread G. trabeum but also that G. trabeum did not survive in the presence of C. formosanus. Further investigation of this antagonistic interaction between this termite and fungus led to a hypothesis that green-spored fungi may be carried by termites and that they play a role in suppressing the growth of G. trabeum. Fungal cultures were isolated from integument and guts of laboratory-maintained colonies of C. formosanus and groups of C. formosanus freshly collected from the field. Only the green-spored fungi were selected from the many fungi isolated. Green-spored fungi isolated from the integument were identified as Aspergillus flavus Link, Trichoderma harzianum Rifai, Trichoderma virens Miller et al., Trichoderma asperellum Samuels, Lieckfeldt & Nirenberg, and Trichoderma ghanense Y. Doi, Y. Abe & J. Sugiyama. A different set of fungi were isolated from the gut, which included A. flavus, Hypocrea virens Chavarri, Samuels and Steward, T. asperellum cultures along with Penicillium janthinellum Biourge and Cladosporium cladosporioides (Fres.) de Vries. A. flavus was associated with every laboratory maintained colony but was associated only with one replication of one of the field collected groups. Our results suggest that A. flavus may be contaminating the colonies that were maintained in the laboratory and the fungus may become proliferous as the colonies become weak. Dual culture tests showed that all the fungi isolated from the integument, and gut were parasites and/or antagonists and that they effectively controlled the growth of G. trabeum. We think termites may be using parasitic fungi to control a brown rot fungus.

Population genetics of the frog-killing fungus Batrachochytrium dendrobatidis

Global amphibian decline by chytridiomycosis is a major environmental disaster that has been attributed to either recent fungal spread or environmental change that promotes disease. Here, we present a population genetic comparison of Batrachochytrium dendrobatidis isolates from an intensively studied region of frog decline, the Sierra Nevada of California. In support of a novel pathogen, we find low diversity, no amphibian-host specificity, little correlation between fungal genotype and geography, local frog extirpation by a single fungal genotype, and evidence of human-assisted fungus migration. In support of endemism, at a local scale, we find some diverse, recombining populations. Therefore neither epidemic spread nor endemism alone explains this particular amphibian decline. Recombination raises the possibility of resistant sporangia and a mechanism for rapid spread as well as persistence that could greatly complicate global control of the pathogen.

Asian origin and rapid global spread of the destructive dry rot fungus Serpula lacrymans

The dry rot fungus Serpula lacrymans (Basidiomycota) is the most damaging destroyer of wood construction materials in temperate regions. While being a widespread aggressive indoor biodeterioration agent, it is only found in a few natural environments. The geographical source of spread and colonization by this fungus in human environments is thus somewhat of an enigma. Employing genetic markers (amplified fragment length polymorphisms, DNA sequences and microsatellites) on a worldwide sample of specimens, we show that the dry rot fungus is divided into two main lineages; one nonaggressive residing naturally in North America and Asia (var. shastensis), and another aggressive lineage including specimens from all continents, both from natural environments and buildings (var. lacrymans). Our genetic analyses indicate that the two lineages represent well-differentiated cryptic species. Genetic analyses pinpoint mainland Asia as the origin of the aggressive form var. lacrymans. A few aggressive genotypes have migrated worldwide from Asia to Europe, North and South America and Oceania followed by local population expansions. The very low genetic variation in the founder populations indicate that they have established through recent founder events, for example by infected wood materials transported over land or sea. A separate colonization has happened from mainland Asia to Japan. Our data also indicate that independent immigration events have happened to Oceania from different continents followed by admixture.

A model of cerebral aspergillosis in non-immunosuppressed nursing rats

Central nervous system aspergillosis is an often fatal complication of invasive Aspergillus infection. Relevant disease models are needed to study the pathophysiology of cerebral aspergillosis and to develop novel therapeutic approaches. This study presents a model of central nervous system aspergillosis that mimics important aspects of human disease. Eleven-day-old non-immunosuppressed male Wistar rats were infected by an intracisternal injection of 10 mul of a conidial suspension of Aspergillus fumigatus. An inoculum of 7.18 log(10) colony-forming units (CFU) consistently produced cerebral infection and resulted in death of all animals (n = 25) within 3-10 days. Median survival time was 3 days. Histomorphologically, all animals developed intracerebral abscesses (2-26 per brain) containing abundant fungal hyphae and neutrophils. Fungal culture of cortical homogenates yielded maximal growth on day 3 after infection (5.4 log(10) CFU/g, n = 15) that declined over time. Galactomannan concentrations in cortical homogenates, assessed as an index for hyphal burden, peaked on days 3-5. Fungal infection spread to peripheral organs in 83% of animals. Fungal burden in lung, liver, spleen and kidney was two orders of magnitude lower than in the brain. The successful establishment of a model of cerebral aspergillosis in a non-immunosuppressed host provides the opportunity to investigate mechanisms of disease and to develop novel treatment regimens for this commonly fatal infection.

Chemical-induced resistance against powdery mildew in barley: the effects of chitosan and benzothiadiazole

Chitosan (CHT), a deacetylated chitin derivative, and benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH), a non toxic synthetic functional analogue of salicylic acid, were applied as foliar spray to barley plants (Hordeum vulgare L.), to compare their effectiveness in inducing resistance against Blumeria graminis f. sp. hordei and to investigate the underlying defence response. After an induction phase of 3 days (IP, time elapsed between treatment and fungal inoculation) both compounds reduced significantly the infection on the primary leaf, namely of 55.5% for CHT and of 68.9% for BTH, showing the induction of a good level of local resistance (LAR). A 5-day IP further reduced the infected areas in BTH treated plants (−77.2%) but not in CHT treated ones (−47.1%). Furthermore, both CHT and BTH also induced SAR, being the infection in the second non treated leaves reduced of 57% and 76.2%, respectively, as evaluated at 10-day IP. Both BTH and CHT induced oxidative burst and phenolic compound deposition in treated leaves, creating an hostile environment that slowed down the fungal spreading by impairing haustorium development. However, the greater efficacy of BTH was possibly due to: i) a greater reinforcement of papilla; ii) a higher level and the more homogeneous diffusion of H2O2 in the treated leaf tissues and iii) an induced hypersensitive-like response in many penetrated cells.