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Enhancement of a pentacyclic tyrosine kinase inhibitor production in Cladosporium cf. cladosporioides by Cladosporol
Full text linkThe binaphthyl derivative cladosporol A was
supplied from 60 to 200 mg l−1 to shaken cultures of Cladosporium cf. cladosporioides. Compared to blank, fungal
biomass was not affected by adding cladosporol till 100 mg l−1: it rather increased at higher ratios between 150
and 200 mg l−1. The production of the major pentacyclic metabolite 1, a cytokine production and tyrosine kinase inhibitor, was enhanced tenfold when cladosporol was
supplied at the highest ratio (200 mg l−1) to shaken growing cultures of the fungus. The bioconversion of cladosporol to cladosporol D through reductive cleavage of the epoxide group was also observed. Interest in this kind of metabolites lies in their potential activity vs DNA topoisomerase I
Biocontrol of Rust Fungi by Cladosporium tenuissimum
Full text linkThis chapter examines whether Cladosporium
tenuissimum Cooke, a destructive
hyperparasite of rust spores, can be
exploited as a BCA of rust fungi. It reports on
tests carried out to evaluate C. tenuissimum
effectiveness against rusts in the genera
Melampsora, Cronartium, Peridermium,
Uromyces and Puccinia, focusing on its
modes of action, the fine-level analysis of
the fungal host–hyperparasite interface, the
antifungal compounds it produces, and its
ability to reduce disease, both in vitro and in
planta. Since effective biological control is
impossible without due consideration of the
ecology of the BCA, as well as of the other
partners involved, and an examination of
their spatial relationships and interaction
with the environment, attention is also paid
to the biological nature of the fungus,
in particular to those characteristics that
enable it to survive in natural habitats and
retain activity under varying environmental
conditions
Acremines H–N, novel prenylated polyketide metabolites produced by a strain of Acremonium byssoides
Full text linkFive novel metabolites, acremines H–N, have been isolated from malt extract–peptone–glucose agar
cultures of a strain of Acremonium byssoides. Their structures and stereochemistry were elucidated using
a combination of 13C and 1H homo and heteronuclear 2D NMR experiments. Acremines H–N inhibited
the germination of sporangia of Plasmopara viticola
Integrazione di caratteri molecolari, micro-morfologici e chemiotassonomici per la caratterizzazione di Cladosporium tenuissimum, iperparassita di agenti di ruggine
No full textThe results of far-reaching investigations on strains of the rust hyperparasite Cladosporium tenuissimum are presented here. The micromorphology of three mycophylic Cladosporium species obtained from public culture collections was analyzed by means of SEM and compared with that of four C. tenuissimum strains isolated from aecidiospores of Cronartium flaccidum and Peridermium pini in different European areas. Such fungi were also compared for their ability to produce secondary metabolites in vitro. SEM observations revealed strong differences in shape and size among conidia of the investigated species: in particular, in C. herbarum and C. tenuissimum they were baculate, and in C. cladosporioides and C. sphaerospermum they presented a streaked-wrinkled ornamentation; moreover they were smaller and rather roundish in C. sphaerospermum, while in C. herbarum, C. cladosporioides and C.tenuissimum they were oblong. Unlike the other Cladosporium spp., C. tenuissimum strains produced in culture a typical yellow pigmentation, diffusible in the agar medium, constituted by a family of related meatbolites, the cladosporols A-E. Such compounds had antifungal activity as inhibitors of germination of Uromyces appendiculatus urediniospores, and reduced the radial growth of several other phytopathogens. The analysis of informative DNA regions has highlighted the occurrence of sequence variants suitable to distinguish C. tenuissimum from the congeneric species C. sphaerospermum, C. cladosporioides, C. oxysporum and C. herbarum. The hyperparasite displayed with these species a sequence homology of 94.6, 96.3, 94.4 and 95.2% respectively in a 540bp fragment from ITS1-5.8S-ITS2 region of rDNA. The internal 5.8 S gene turned out to have identical lenght (161bp) in all the species except C.herbarum (160bp). The only differences in the gene were a T-C transition at residue 13 in C. sphaerospermum, a G-T transversion at residue 21 in C. cladosporioides, another transversion at residue 81 in C.tenuissimum and a loss of a G residue at position 141 in C.herbarum. Microscopic observations already made at the interface between C.tenuissimum and Cronartium flaccidum or Uromyces appendiculatus confirmed an active hyperparasitism of rust spores by C. tenuissimum. These investigations need further in-depth studies taking into consideration the ecology of the hyperparasite and the favourable environmental conditions which seem to support this active intraction. The analysis of independent distinguishing features, like cultural, morphological and chemical characters, supplemented with biomolecular investigations, enabled us to verify the adequacy of taxonomic positioning of the hyperparasite strains in C. tenuissimum species and constitute a valuable approach to examine in detail the nature of the hyperparasite
Hystological studies on the mycoparasitism of Cladosporium tenuissimum and urediniospores of Uromyces appendiculatus
No full textInteractions between the mycoparasite Cladosporium tenuissimum and the bean rust Uromyces appendiculatus were
studied through light and electron microscopy in vitro at the host–parasite interface. Urediniospore germination
decreased on contact with ungerminated C. tenuissimum conidia, possibly due to antibiosis mechanisms. C. tenuissimum
grew towards the bean rust spores and coiled around their germ tubes. Penetration of the urediniospores occurred either
enzymatically and/or mechanically, through appressorium or infection cushion structures, from which a thin penetrating
hypha was generated. Enzyme production by the mycoparasite was suggested by the loosening of the matricial
components of the spore wall, which sometimes left chitin fibrils visible. Mycoparasite hyphae grew within the host
spore, emptied its content, and emerged profusely forming conidiophores and conidia. C. tenuissimum was able to grow
on media containing laminarin, suggesting the ability of producing glucanases, but not when chitin was used as the sole
carbon source. Conidia that had been grown on a sugar-rich medium, filtered, and extracted with organic solvents, were
found to contain cladosporol and related compounds. Complete control of the bean rust disease was achieved by
application of C. tenuissimum culture filtrates but not by conidial suspensions. This is the first report of parasitism by
C. tenuissimum on U. appendiculatus. These investigations provide additional observations on a genus besides
Melampsora and Cronartium from which this fungus has been isolated and tested to date. The possible role of
environmental factors for the exploitation of this organism as a biocontrol agent is also mentioned
Effect of phlobaphene accumulation in maize kernel on Fusarium ear rot level in Lombardia
No full textFusarium ear rot (FER) is one the most serious maize fungal diseases especially in Lombardia, the most important maize producer region in Italy. The main aetiological agents of FER are Fusarium species belonging to Gibberella fujikuroi species complex, in particular F. verticillioides and F. proliferatum. FER usually does not lead to significant yield losses, but its causal agents are well known producers of mycotoxins such as fumonisins. Control measures in Italy consist of one - two treatments against the European corn borer, but additional preventive means are required in order to assure a more effective protection. Breeding efforts have been undertaken to increase resistance to FER and in particular phlobaphenes seem to be able to reduce the fumonisin accumulation in kernels.
The aim of this study was to assess the effect of pericarp phlobaphenes on FER rating under field conditions. Two hybrids, one with P1-rr allele providing pigmentation in pericarp and the other carrying P1-wr allele without phlobaphenes accumulation in pericarp, were sown in 2011 and 2012 in four different locations in Lombardia. The frequency and severity of FER, together with the incidence of latent infections caused by G. fujikuroi clade and the fumonisin content, were assessed in each genotype at the four field trials.
Significant but not univocal differences in FER frequency and severity between the two genotypes were found only in 2012. Latent infections were significantly more frequent on P1-wr genotype in two fields and on P1-rr in the same location for two years. A similar distribution pattern was also found in the fumonisin level. Statistical analysis showed that FER indexes are positively correlated with both latent infections and fumonisin accumulation and significantly influenced not only by the presence of phlobaphenes, but also by the field location and the year of cultivatio
Antimicrobial activity of some Sri Lankan Rubiaceae and Meliaceae
Full text linkNinety solvent extracts (n-hexane, dichloromethane and methanol) obtained from the leaves, bark and stem of 13 Sri Lankan Rubiaceae and two Sri Lankan Meliaceae plants have been screened for antibacterial and antifungal activities. Morinda tinctoria, Mussaenda frondosa, Psychotria gardneri and Psychotria stenophylla displayed the widest spectrum of
antibacterial activity
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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