Chronopathological aspects of disease incidence in rice (Oryza sativa L.)

Rice seedlings maintained under uncontrolled glasshouse conditions were inoculated with conidial suspensions of a fungal pathogen, Helminthosporium oryzae, at various times during the 24 h. Significant increase in the percent germination and germ tube length of conidia were observed in the rice samples inoculated at 02:00 and 06:00h. The 24 h temporal variation in leaf temperature was positively correlated with variation in stomatal movements. The results indicate a 24 h rhythm in the behavior of the fungal pathogen on the host in relation to the conditions of the growing environment. In all the inoculated seedlings, the appearance of a large number of brown leaf spots was confined to the light span. Among the plants inoculated, earlier initiation of brown leaf spot appearance, maximum number of leaf spots, and highest disease severity were observed when plants were inoculated at 02:00h. There was a positive correlation between disease severity of the host and in vivo values of percent germination of conidia and germ tube length of the pathogen in plants inoculated between 02:00 and 06:00h. The findings of this study implicate that light intensity and temperature could play a predominant role in controlling disease susceptibility rhythms in plants.     

Exudate from sporulating cultures of Hirsutella thompsonii inhibit oviposition by the two-spotted spider mite Tetranychus urticae

The acaricidal mycopathogen Hirsutella thompsonii has been found to secrete metabolites that are active against femaleTetranychus urticae. Specifically, the rose-colored exudate produced on sporulating cultures of Mexican HtM120I strain sterilized female spider mites in a dose-dependent fashion. Topical application of the exudate resulted in a 100% reduction in mite fecundity over the initial six days of experimentation. Depending upon the exudate dosage, mites partially recovered within 3 and 6 d post-treatment and produced a limited number of eggs. The spider mite active HtM120I exudate contained less detectable HtA toxin than the HtM120I broth filtrate, and it was innocuous when injected into the greater wax moth Galleria mellonella L. larvae. Broth filtrates of HtM120I cultures, although toxic to assayed G. mellonella larvae, did not inhibit mite oviposition to the degree or duration of the exudate preparations. These findings suggest that the factor responsible for suppressing oviposition in female spider mites is linked to the sporulation process and is distinct from the well-characterized HtA produced by vegetative cells. This revised version was published online in July 2006 with corrections to the Cover Date.     

Extensive MHC class I-restricted CD8 T lymphocyte responses against various yeast genera in humans

The human cellular immune response against 14 distantly related yeast species was analyzed by intracellular cytokine staining of lymphocytes after ex vivo stimulation of whole blood. While the CD4 T cell response was marginal, extensive MHC class I-restricted CD8 T cell responses were detected against a number of species including spoiling, environmental and human pathogenic yeasts. The yeast-specific CD8 T cells expressed interferon-gamma but lacked expression of CD27 and CCR7, indicating that they were end-differentiated effector memory cells. Mainly intact yeast cells rather than spheroplasts were able to induce cytokine expression in T cells demonstrating that the dominant immunogens were located in the yeast cell wall. Together these data underline the importance of the cellular immune response in protecting humans against yeast and fungal infections. And, from another perspective, recombinant yeast suggests itself as a potential vaccine candidate to efficiently induce antigen-specific CD8 T cell responses.     

Humus bacteria of Norway spruce stands: plant growth promoting properties and birch, red fescue and alder colonizing capacity

We studied the potential of the humus layer of the Norway spruce stands to supply beneficial rhizobacteria to birch (Betula pendula), alder (Alnus incana) and fescue grass (Festuca rubra), representatives of pioneer vegetation after clear-cutting of the coniferous forest. Axenically grown seedlings of these species were inoculated with the acid spruce humus, pH 3.7-5.3. Actinorhizal propagules, capable of nodulating alder, were present in high density (10(3) g(-1)) in humus of long-term limed plots, whereas plots with nitrogen fertilization contained almost none (相似文献   

Evaluation of the pathogenicity and infectivity of entomopathogenic hypocrealean fungi,isolated from wild mosquitoes in Japan and Burkina Faso,against female adult Anopheles stephensi mosquitoes

We investigated the potential of entomopathogenic hypocrealean fungi that naturally occur in or on adult mosquitoes for use as biocontrol agents of vector mosquitoes. The fungi were isolated from wild mosquitoes collected in Japan and Burkina Faso using two isolation methods (with and without surface sterilization). Detected fungal species included Beauveria bassiana sensu lato, Isaria spp., Paecilomyces spp., Lecanicillium spp., and Simplicillium spp. These isolates were used in bioassays against adult female Anopheles stephensi mosquitoes. The median survival time ranged from 5.8 to 14.9 d (control, 17.0 d). Reduced survival times were observed in the isolates from surface-sterilized mosquitoes from Japan, with the isolate B. bassiana s.l. 60-2 exhibiting the highest virulence. This study indicates that adult mosquitoes are naturally infected with various entomopathogenic hypocrealean fungi, and that some of these isolates have the potential for use as fungal pesticides to control vector mosquitoes.     

Maxent modeling for predicting the potential distribution of Sanghuang,an important group of medicinal fungi in China

The ability to identify the spatial distribution of economically important fungal species is crucial for understanding the environmental factors that affect them and for conservation management. A potentially valuable approach for this is maximum entropy (Maxent) spatial distribution modeling, which was applied here to map the potential distribution of three “Sanghuang” mushrooms in China, which include Phellinus baumii, Phellinus igniarius and Phellinus vaninii. Nineteen WorldClim bioclimatic variables, with corresponding altitude data, and 89 spatially well-dispersed species occurrence records were used in the modeling. The relative importance of the environmental variables was evaluated by Jackknife tests in the modeling analysis. The maximum entropy models obtained have high Area Under Receiver Operating Characteristic Curve (AUC) values: 0.956, 0.967 and 0.960, for P. baumii, P. igniarius and P. vaninii, respectively. The bioclimatic variable that most strongly affected distributions of P. baumii and P. vaninii was precipitation in the warmest quarter, while the mean temperature in the warmest quarter affected the distribution of P. igniarius most strongly. Overall, these models could provide valuable help in searching for the target species in areas where it is hitherto unknown, and be the reference of conservation measures for these medicinal fungal species.     

Enzymatic systems involved in decomposition reflects the ecology and taxonomy of saprotrophic fungi

One hundred and eleven strains of Basidiomycota, 39 strains of Ascomycota and 2 strains of Mucoromycotina belonging to wood decomposers that cause white-rot (WR) or brown-rot (BR), other wood associated saprotrophs (WA), litter decomposing cord-forming Basidiomycota (LDF), and saprotrophic microfungi (SA), were screened for the production of hydrolytic enzymes and laccase. The presence of enzyme-encoding genes was also analysed in the published genomes of saprotrophic fungi. Several genes, including those for acidic phosphatase, β-glucosidase and N-acetylglucosaminidase, were common in the genomes with enzyme activity widely displayed by fungi, while other enzymes, such as certain hemicellulases or laccase, were produced less frequently. Enzyme production by saprotrophic fungi was shaped by the combination of their ecophysiology and taxonomy. Basidiomycota exhibited higher activities of all enzymes, except alkaline phosphatase, α-glucosidase, N-acetylglucosaminidase, α-mannosidase and α-fucosidase, than Ascomycota. The SA and BR fungi showed distinct enzyme production patterns, while the enzyme production by WR, LDF and WA was similar. Differences among species were typically reflected in the level of enzyme activity rather than in the absence of enzymes. Enzyme screening results showed that in several cases, fungi exhibited enzyme activity without the presence of the corresponding gene and vice versa. This indicates that the use of genome-derived information for the prediction of potential enzyme production has substantial limitations and cannot replace functional screening of fungal cultures.     

Heart rot hotel: fungal communities in red-cockaded woodpecker excavations

Tree-cavity excavators such as woodpeckers are ecosystem engineers that have potentially complex but poorly documented associations with wood decay fungi. Fungi facilitate cavity excavation by preparing and modifying excavation sites for cavity excavators. Associations between fungi and endangered red-cockaded woodpeckers (RCWs) are particularly interesting because these are the only birds that specialize in excavating into the heartwood of living pines, a process that takes years to complete. Using molecular methods, we examined fungal communities in complete and incomplete RCW excavations, and non-cavity control trees. In addition to finding a high diversity of fungi, we found three groupings of fungal communities corresponding to the three groups of trees sampled. We show that trees selected for cavity excavation by RCWs are infected by distinct fungal communities, and propose two hypotheses to explain this outcome: the bird facilitation hypothesis and the tree selection hypothesis.     

Distribution,occurrence and natural invertebrate hosts of indigenous entomopathogenic fungi of Central India

We report here that, during periodical surveys of insects inhabiting diverse habitats for the collection of entomopathogenic fungi; a large number of isolates were recovered belonging to seven species, from various regions of Madhya Pradesh and Chhattisgarh forest areas and agricultural fields. The most common entomopathogenic fungi such as Beauveria bassiana, Nomuraea rileyi, Paecilomyces farinosus and Paecilomyces fumosoroseus were found to infect various insect hosts species naturally viz. Hyblaea puera, Eutectona machaeralis, Diachrysia orichalcea, Spodoptera litura, and few new insect hosts of these fungal pathogens among Indian insect population were collected for the first time from Central India, such as beetles of Agrilus species, hairy caterpillars of Lymantria species. The isolation, identification, maintenance and pathogenicity assay of these isolates was performed prior to deposition in culture collection center.     

Development of a Real-Time PCR assay for quantitative assessment of uncultured freshwater zoosporic fungi

Recently, molecular environmental surveys of the eukaryotic microbial community in lakes have revealed a high diversity of sequences belonging to uncultured zoosporic fungi. Although they are known as saprobes and algal parasites in freshwater systems, zoosporic fungi have been neglected in microbial food web studies. Recently, it has been suggested that zoosporic fungi, via the consumption of their zoospores by zooplankters, could transfer energy from large inedible algae and particulate organic material to higher trophic levels. However, because of their small size and their lack of distinctive morphological features, traditional microscopy does not allow the detection of fungal zoospores in the field. Hence, quantitative data on fungal zoospores in natural environments is missing. We have developed a quantitative PCR (qPCR) assay for the quantification of fungal zoospores in lakes. Specific primers were designed and qPCR conditions were optimized using a range of target and non-target plasmids obtained from previous freshwater environmental 18S rDNA surveys. When optimal DNA extraction protocol and qPCR conditions were applied, the qPCR assay developed in this study demonstrated high specificity and sensitivity, with as low as 100 18S rDNA copies per reaction detected. Although the present work focuses on the design and optimization of a new qPCR assay, its application to natural samples indicated that qPCR offers a promising tool for quantitative assessment of fungal zoospores in natural environments. We conclude that this will contribute to a better understanding of the ecological significance of zoosporic fungi in microbial food webs of pelagic ecosystems.