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Interaction between Esca-Associated Fungi, Grapevine Calli and Micropropagated Shoot Cultures of Grapevine
Full text linkCallus of the grapevine cv. Italia, micropropagated shoot cultures of the cv. Italia, Matilde and Sangiovese
and callus of the tobacco cv. White Burley were cultivated on modified LS and MS-media. Phaeomoniella chlamydospora
(Pch), Phaeoacremonium aleophilum (Pal) and Fomitiporia punctata (Fop) grew well in the presence of calli and
vitroplants of all the grapevine cultivars which stimulated the growth of the fungi, but growth of the calli and vitroplants
was reduced. All three fungi inhibited callus growth more strongly in grapevine than in tobacco. Fop had the greatest
inhibitory effect on grapevine callus. Symptom severity also differed between cultivars. All three fungi invaded callus
tissue after entirely overgrowing its surface. Hyphae were observed within the callus mass, where several cellular
aggregates showed melanin-like deposits, particularly when invaded by Pal. On the foliar lamina of vitroplants
symptoms were produced before and after the invasion of the plantlets by each fungus. Symptoms consisted in light
green or chlorotic, rounded or irregular spots between the veins or along the leaf margin. The combination Pal vs.
vitroplant gave the fastest host-pathogen response. The susceptibility or resistance of calli or vitroplants to escaassociated
fungi could be a means to select grapevine for resistance to these fungi
Occurrence and distribution of sugar beet viruses in Lebanon
No full textField surveys were carried out in the main sugar beet growing areas of Lebanon to assess the occurrence
and distribution of viral diseases. A total of 1002 samples from 115 commercial fields were serologically assessed for
Beet Necrotic Yellow Vein Furovirus (BNYVV), Beet Yellows Closterovirus (BYV), Beet Mosaic Potyvirus (BtMV), Beet
Western Yellow Luteovirus (BWYV) and Cucumber Mosaic Cucumovirus (CMV). ELISA tests revealed that 39.5% of
samples were infected with one or more viruses. BtMV was the most common (56.5%), followed by BYV (29.5%),
BNYVV (17%) and BWYV (11%). Mixed infections were detected in 5.2% of the samples. CMV was not encountered.
Direct tissue printing of plants infected with BtMV, BYV and BWYV on a nitrocellulose membrane gave very strong
positive reactions
The structure of the exopolysaccharide fraction from Pseudomonas savastanoi strain ITM519 and the defence-response it induces in non-hosts plants
Full text linkThe main exopolysaccharide (EPS) obtained from the phytopathogenic bacterium Pseudomonas savastanoi
pv. nerii, strain ITM519, has a very complex highly branched structure consisting of fucose, galactose, Nacetylgalactosamine
and N-acetylglucosamine. EPS triggers a defence response in non-host plant cells. This capability
could be a consequence of the complex and heterogeneous structure of the molecule, part of which might mimic
elicitors produced in the plant–pathogen interaction
Specific SCAR Primers for Fungi Associated with Wood Decay of Grapevine
Full text linkRAPD (Random Amplified Polymorphic DNA) analysis, a technique based on the polymerase chain reaction,
was applied to explore variation in 178 isolates of Fomitiporia punctata, 94 of Phaeomoniella chlamydospora
and 34 of Phomopsis viticola, selected as being representative of fungal populations from different vineyards and
locations. The analysis showed a broad genetic variability in F. punctata and a very high genetic uniformity in P.
chlamydospora. With P. viticola, isolates belonging to different vegetative compatibility groups were investigated;
the analysis evidenced high genetic similarity among isolates within groups and broad inter-group variation. For
each pathogen, specific RAPD markers were selected, cloned and sequenced. The obtained sequences were used to
design sequence-characterised amplified region (SCAR) primers specific for each pathogen. These are being used to
develop molecular diagnostic tools
Interactions between Three Fungi Associated with Esca of Grapevine, and Their Secondary Metabolites
Full text linkThe effect of the culture filtrates, crude organic extracts of culture filtrates, metabolites such as scytalone,
pullulan and oligosaccharides produced by three fungi associated with esca, Phaeomoniella chlamydospora (Pch),
Phaeoacremonium aleophilum (Pal) and Fomitiporia punctata (Fop), on the growth of the fungi themselves, was
studied in vitro. At 1:1 dilution, the culture filtrates of Pal and Pch inhibited Fop completely, whereas at 1:2 dilution
they only increased Fop growth latency. Fop was not inhibited by crude organic extracts of Pal or Pch. Growth of Pal
was slightly stimulated at the lowest concentrations of Pch crude extracts, whereas it was inhibited at the highest
concentration. Scytalone (at 1 mg ml-1), pullulan (at 0.2 mg ml-1) and oligosaccharides up to 2.5 kDa (2 mg ml-1) did not
affect the radial growth of Fop
Lantana camara in the soil changes the fungal community structure and reduces impact of Meloidogyne javanica on mungbean
No full textChanges in the fungal community resulting from nematode suppression were studied by comparing the
number of fungal species in the soil and mungbean roots between soils with and without amendment with Lantana
camara. Addition of L. camara to the soil at 1% (w:w) significantly reduced the Meloidogyne javanica population
density in the soil and in the roots of mungbean, as well as subsequent root-knot infestation of mungbean, confirming
that nematode suppressiveness was induced by this organic amendment. L. camara amendment was associated with
an increase in fungal populations, especially those with nematicidal activity. The soil was probably the major source
of fungal endophytes in mungbean roots since nearly all the endophytic fungi were also found in the soil. L. camaraamended
soils contained several fungi that were not found in unamended soil, including an Acremonium sp., Aspergillus
fumigatus, Drechslera australiensis, Fusarium culmorum, Penicillium notatum and Trichoderma viride.
The fungi in the inner root tissues of mungbean growing in L. camara-amended soil included an Acremonium sp., F.
solani, Macrophomina phaseolina, Penicillium sp., and Trichoderma viride. Only T. viride was not encountered in
the inner root tissues of mungbean in unamended soil. M. phaseolina and F. solani were isolated with relatively high
frequency from the inner root tissues of mungbean growing in unamended soils while the remaining endorhizal fungi
were more frequent in amended soils. M. phaseolina, though isolated extensively from the inner root tissues, either
did not occur in the soil or was not isolated by the soil dilution technique used. When fungi from soil amended with L.
camara were tested for their nematicidal and hatch-inhibiting activity, Aspergillus niger produced the greatest nematode
mortality, while T. viride caused the greatest inhibition of egg hatching of M. javanica