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Background: Systemic Epichloë endophytes are common fungal symbionts of many cool-season grasses. They are known for their capability of increasing host plant tolerance against biotic and abiotic stressors, including grass pathogens. However, results on endophyte-mediated disease resistance have been ambiguous, and the underlying mechanisms of disease resistance remain unknown. Aims: We studied how Epichloë endophytes affect naturally occurring pathogen, leaf blotch (Rhynchosporium sp.), infections of wild and cultivated tall fescues (Schedonorus phoenix). Methods: Endophytic and endophyte-free tall fescues were grown in a common garden experiment in southern Finland for eight growing seasons. The experimental plants were subjected to nutrient and water treatments. Results: Our results show that the effects of endophytes on leaf blotch infection incidences varied with plant origins and environmental conditions. Overall, the American cultivar 'Kentucky-31ʹ appeared to have less disease symptoms compared to the Finnish cultivar 'Retu' or the wild grasses. Endophytic wild tall fescues from Gotland Island had lower Rhynchosporium incidences than grasses from Åland Islands or coastal Sweden. Conclusions: These results show that Epichloë endophytes can suppress pathogen Rhynchosporium infections in tall fescues, but pathogen resistance depends on grass origin and environmental conditions. [ABSTRACT FROM AUTHOR]

A growth assay was established for the barley pathogen Rhynchosporium commune with EGFP-tagged fungal mutants. This assay was used to study the effect of four antibiotics (hygromycin B, nourseothricin, kanamycin, phleomycin) and a herbicide (phosphinothricin) on fungal development. Fitting the growth curves to the modified Gompertz model allowed calculating growth parameters, such as lag periods of fungal colony formation and mycelial growth rates as well as EC50 values. Except kanamycin all compounds were efficient inhibitors so that the corresponding resistance-conferring genes can be used as markers for selection of fungal transformation-based mutants. In addition the assay was used to quantify the inhibitory activity of a barley secondary metabolite, the indole alkaloid gramine. [ABSTRACT FROM AUTHOR]

Rhynchosporium consists of two species, R. secalis and R. orthosporum. Both are pathogens of grasses with R. secalis infecting a variety of Poaceae hosts and R. orthosporum infecting Dactylis glomerata. Phylogenetic analyses of multilocus DNA sequence data on R. secalis isolates originating from cultivated barley, rye, triticale and other grasses, including Agropyron spp., Bromus diandrus and Hordeum spp., resolved the monophyletic groups into three species according to their respective hosts. Host specificity according to phylogenetic lineages was confirmed with pathogenicity studies. Because R. secalis was described first on rye this name is retained for Rhynchosporium isolates infecting rye and triticale. Rhynchosporium isolates infecting cultivated barley and other Hordeum spp. and Bromus diandrus belong to a distinct species, R. commune. Similarly isolates infecting Agropyron spp. represent a distinct species of Rhynchosporium, namely R. agropyri. A PCR-RFLP assay was developed as a rapid tool for species identification of R. secalis and R. commune. [ABSTRACT FROM AUTHOR]

Plectosporium alismatis is a fungal pathogen that is being investigated as a biocontrol agent for suppressing starfruit (Damasonium minus), a significant weed of Australian rice fields. The aim of this research was to study the effect of the fungus on weed competition and its interactions with chemical herbicides. Conidial germination was significantly reduced by Londax® (bensulfuron-methyl), while MCPA had no effects. Glasshouse trials showed evidence of synergism between the fungus and 1.56% of the recommended dose of Londax®, in reducing the weed growth. The application of inoculum (conidia suspended in water) in the glasshouse eliminated weed competition with rice. In the field, the reduction in weed growth caused by the fungus did not significantly eliminate starfruit competition with rice. This is thought to be due to the presence of other weeds. [ABSTRACT FROM AUTHOR]

The objective of this work was to evaluate the production of chlamydospores and conidia of Rhynchosporium alismatis in a liquid Czapex-Dox based medium supplemented with increasing concentrations of sodium nitrate and malt extract. In addition, the germination of chlamydospores was evaluated. A high concentration of malt extract (4.4 g L -1 ) as the sole carbon source and a high level of sodium nitrate as the sole nitrogen source (3.3 g L -1 ) were shown to increase chlamydospore production while agitation (150 rpm) enhanced conidial yields. Maximum chlamydospore production (2.03×10 5 ±0.7 total chlamydospores mg DW -1 ) was achieved in cultures grown in a medium supplemented with 8.8 g L -1 malt extract and 5.74 g L -1 sodium nitrate. Two days growth was required for maximum chlamydospore and conidial production, while 6 days was necessary to obtain maximum dry weight accumulation (350 mg per flask). Germination of chlamydospores (90%) was significantly higher than germination of conidia (47%) after 2 days growth. [ABSTRACT FROM AUTHOR]

The fungal pathogen Rhynchosporium alismatis is being developed for biological control of starfruit ( Damasonium minus ), an important aquatic weed in Australian rice fields. The development of R. alismatis in starfruit differs between juvenile and adult plants. Juvenile starfruit plants are stunted as a result of fungal infection, while in adult plants, the main effect is necrosis and chlorosis of floating leaves. A conidial concentration of 1×10 4 conidia mL -1 was adequate to cause disease symptoms on floating leaves, but the stunting effect on juveniles was caused by concentrations of at least 1×10 5 conidia mL -1 . To successfully inoculate juvenile plants, the water must be drained before inoculation to expose plants to the inoculum. The artificial addition of dew periods did not enhance disease development in plants. The stunting of juvenile starfruit plants caused by the infection of R. alismatis may give rice plants a competitive advantage over the weed at the seedling stage [ABSTRACT FROM AUTHOR]

Examines the influence of nutrition on conidial production by Rhynchosporium alismatis in Australia. Correlation between image analysis of diseased leaf discs and low visual assessment; Determination on the fitness of Conidia in small-scale biofermentors; Use of bioassay on Alisma lanceolatum leaves.