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Infected Trees (infected + tree)
Selected AbstractsEpidemiology of Plum pox virus strain M in GreeceEPPO BULLETIN, Issue 2 2006C. Varveri Plum pox virus has been endemic in Greece since 1967 causing important losses in apricot and to a lesser extent in peach crops. A survey undertaken in 1992 in public and private mother-tree plantations to estimate its incidence revealed that the virus was absent in isolated areas far from commercial stone-fruit crops. Virus titers decrease significantly during the hot months in the infected trees but re-increase in October,November permitting reliable detection. It is virulent M-type isolates which are effectively transmitted by aphids that are mostly recovered. Aphis gossypii and Hyalopterus pruni were the most abundant virus vectors captured during the small scale monitoring undertaken in apricot orchards in 1999 and 2000. Virus spread was monitored in two apricot orchards from 1996 to 2000 and analysed. Initial infections followed a completely random spatial pattern, while loose clusters appeared in succeeding years, to finally reach a uniform distribution representing high infection levels. The nearby ecological conditions greatly affected the rate of disease development. [source] Xanthomonas citri: breaking the surfaceMOLECULAR PLANT PATHOLOGY, Issue 3 2003Asha M. Brunings SUMMARY Taxonomy: Bacteria; Proteobacteria, Gammaproteobacteria; Xanthomonadales; Xanthomonadaceae, Xanthomonas. Microbiological properties: Gram-negative, obligately aerobic, straight rods, motile by a single polar flagellum, yellow pigment. Related species:X. campestris , X. axonopodis , X. oryzae , X. albilineans . Host range: Affects Rutaceous plants, primarily Citrus spp., Fortunella spp., and Poncirus spp., world-wide. Quarantined pathogen in many countries. Economically important hosts are cultivated orange, grapefruit, lime, lemon, pomelo and citrus rootstock. Disease symptoms: On leaves, first appearance is as oily looking, 2,10 mm, similarly sized, circular spots, usually on the abaxial surface. On leaves, stems, thorns and fruit, circular lesions become raised and blister-like, growing into white or yellow spongy pustules. These pustules then darken and thicken into a light tan to brown corky canker, which is rough to the touch. On stems, pustules may coalesce to split the epidermis along the stem length, and occasionally girdling of young stems may occur. Older lesions on leaves and fruit tend to have more elevated margins and are at times surrounded by a yellow chlorotic halo (that may disappear) and a sunken centre. Sunken craters are especially noticeable on fruit, but the lesions do not penetrate far into the rind. Defoliation and premature abscission of affected fruit occurs on heavily infected trees. Useful websites: Pathogenicity of Phytophthora austrocedrae on Austrocedrus chilensis and its relation with mal del ciprés in PatagoniaPLANT PATHOLOGY, Issue 4 2010A. G. Greslebin Field observations, isolations and pathogenicity tests were performed on Austrocedrus chilensis (Cupressaceae) trees to determine the pathogenicity of Phytophthora austrocedrae and its role in the aetiology of the cypress disease mal del ciprés (MDC) in Argentina. It was found that P. austrocedrae is a primary pathogen of A. chilensis. It was isolated from large necrotic lesions in the inner bark, and superficially in the sapwood, at the root collar and stem, in most of the MDC-affected stands surveyed along the range of A. chilensis in Argentina. The main symptom in naturally infected trees was a necrotic lesion extending from killed roots up to 1 m up the tree bole. Seedlings, saplings and adult trees were all susceptible to inoculation with P. austrocedrae. Under favourable experimental conditions (flooding), inoculated seedlings suffered massive mortality in less than a month. The importance of diseases caused by Phytophthora spp. in South American forests is discussed. [source] Seasonal detection of pear decline phytoplasma by nested-PCR in different pear cultivarsPLANT PATHOLOGY, Issue 4 2003M. Garcia-Chapa Seasonal detection of pear decline phytoplasma was studied in three pear cultivars: Bartlett, Limonera and Blanquilla. Samples from 43 infected trees were collected monthly over 2 years and analysed by nested PCR. The three cultivars each showed a different pattern of phytoplasma detection. The maximum detection rate of pear decline phytoplasma occurred in December in the three orchards, and it remained high throughout the winter months. In spring, when new buds appeared and sap was produced, the detection rate decreased. Leaf midribs, buds and stems were compared to determine which sample was more reliable for phytoplasma detection. The best indicators were stems. The presence of phytoplasma in sieve tubes during the dormant season was determined by grafting. The results suggest that phytoplasmas could overwinter in shoots, with the implication that vegetative propagation during this period could also disseminate the disease. [source]
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