1,721,027 research outputs found
Root and crown tot of olive caused dy Phytophthora spp.
Full text linkPhytophthora root and crown rot has been traditionally considered a minor disease of olive. However, in recent years it has
been recognized as an emerging problem in several olive-growing countries such as Australia, Italy and Spain probably as a
consequence of the expansion of plantings in new areas with heavy soils and the more intensive use of irrigation in both olive nurseries and commercial groves. The disease has been reported from most olive-growing countries and is caused by several soil -borne species of Phytophthora, including P. cinnamomi, P. citricola, P. cryptogea,
P. drechsleri, P. gonapodyides, P. inundata, P. megasperma,P. nicotianae and P.palmivora. Diagnosis is currently based on the
isolation and identification of isolates by both traditional and molecular methods. New molecular techniques are currently available that could be applied for both the identification of isolates and Phytophthora infections directly in host-tissues as well as insoil and water samples. A number of dedicated databases could improve the efficiency of these techniques. Moreover, DNA analysis has greatly contributed to phylogenetic studies of Phytophthora. Control of Phytophthora root and crown rot of olive is mainly based on preventive measures
Impairment of leaf hydraulics in young plants of Citrus aurantium (sour ornage) infected by Phoma tracheiphila
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Characterisation of Phoma tracheiphila by RAPD-PCR, microsatellite-primed PCR and ITS rDNA sequencing and development of specific primers for in planta PCR detection
No full textThirty six isolates of Phoma tracheiphila from Italy, the causal agent of the "mal secco" disease on Citrus species, were characterised by different molecular tools in comparison with representative isolates of other phytopathogenic Phoma species. These included analysis of the distribution of RAPD and microsatellite markers and sequencing of the internal transcribed spacer (ITS) region of the nuclear rRNA genes. The results obtained with 12 RAPD primers (92 markers) and 7 microsatellite primers (56 markers) suggest that Italian isolates of P. tracheiphila are genetically homogeneous, leading to identical patterns upon amplification with all the tested primers. Accordingly, ITSI-5.8S-ITS2 sequences were highly conserved (98-100% identity along a 544-characters alignment) among all the isolates of P. tracheiphila. A neighbor-joining analysis of ITS sequences of P. tracheiphila in comparison with those of other Phoma species, as well as with alignable sequences from anamorphic and teleomorphic taxa retrieved in BLAST searches, revealed a close relationship between P. tracheiphila and Leptosphaeria congesta. A pair of P. tracheiphila-specific primers was designed on the consensus sequence (555 residues) obtained from the alignment of the newly generated P. tracheiphila ITS sequences. A PCR-based specific assay coupled to electrophoretic separation of amplicons made it possible to detect P. tracheiphila in naturally infected Citrus wood tissue collected from both symptomatic and symptomless plants. The limit of detection was 10 pg of genomic DNA and 5 fg of the ITS target sequence
Efficacia del Valifenalate contro specie terricole di Phytophthora patogene di piante ornamentali
No full textI risultati confermano che il valifenalate su piante erbacee e arbustive è un prodotto sistemico e dimostrano che questo p.a., proposto come antiperonosporico, può essere efficace anche contro i marciumi radicali di piante ornamentali causate da specie terricole di Phytophthora
Efficacy of the fungicide valiphenal against crown rot of rose caused by Phytophthora citrophthora
No full textCrown and root rot caused by soilborne species of Phytophthora are common diseases of container-grown ornamental plants in nursery. Crown rot of Rose caused by P. citrophthora has been recently reported in Sicily (southern Italy). Valiphenal (IR 5885) is a systemic dipeptide fungicide of the valinamide class of compounds and is active against Oomycetes. This new fungicide is under development by the italian agrochemical company ISAGRO against powdery mildews of grapevine, potatoes and vegetables. In this study, the efficacy of Valiphenal and other experimental active ingredients was tested for the first time against crown rot of Rose. Phosetyl-Al (Aliette) was used as a reference product. Minigreffe plants of ‘Red France’ Rose on Rosa indica-major as rootstck, grown in pots (diameter 16 cm) in a plastic-house were used in all experiments. Plants were wound inoculated on the stem with agar plugs taken from P. citrophthora colonies growing on potato dextrose agar. Wounds were sealed with Parafilm and symptoms were evaluated at various time intervals after inoculation. Valiphenal, alone or mixed with biostimulants, such as the leaf organic fertilizer Siapton, was applied as foliar spray at the dose of 0.75 g/l a. i., 7 days before the inoculation. In all experiments Valiphenal proved to be as effective as Phosetyl-Al in reducing the length of the cankers on the stems of inoculated plants. Five months after the inoculation, plants treated with Valiphenal or Phosetyl-Al did not show symtoms of stem dieback whereas all nontreated control plants wilted. The addition of Siapton increased the efficacy of Valiphenal but results were not consistent among experiments. No symptoms of phytotoxicity were observed on treated plants
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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