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Lymington, United Kingdom

Katis N.I.,Aristotle University of Thessaloniki | Chatzivassiliou E.K.,Aristotle University of Thessaloniki | Chatzivassiliou E.K.,Agricultural University of Athens | Clay C.M.,Horticulture Research International | And 5 more authors.
Journal of Plant Pathology | Year: 2011

In a 10-year survey several Eggplant mottled dwarf virus (EMDV) isolates were collected from diverse hosts from all over Greece. In this study, an IC-RT-PCR assay was developed for the detection of the virus. Degenerate primers were designed on conserved regions of the glycoprotein (G) gene of various plant nucleorhabdoviruses. Based on the initial genetic information obtained, EMDV-specific primers were subsequently designed. The method successfully amplified a 284 bp product from all (76) virus samples originating from tobacco, cucumber, eggplant, Pittosporum tobira and Capparis spinosa (caper). Sequence analysis and Western blot were done for further characterization of representative isolates. Two isolates from tobacco (EMDV-Tob) and cucumber (EMDV-Cu) were also subjected to electron microscopy and host range studies. Sequence analysis of the partial G gene confirmed the classification of EMDV within nucleorhabdoviruses. Genetic comparisons among the EMDV isolates tested indicated low levels of variation with the caper isolate, which is reported for the first time in Greece, being the most deviating isolate. This is the first molecular assay developed for the detection of EMDV and also the first sequence information obtained of its genome. Source

Munir M.,University of Reading | Munir M.,King Faisal University | Hadley P.,University of Reading | Carew J.,University of Reading | And 3 more authors.
Pakistan Journal of Botany | Year: 2015

After 80% seed germination plants of an early flowering cultivar Chimes White of Antirrhinum were subjected to five set-point temperature regimes (14, 18, 22, 26 and 30°C) for two consecutive years to observe their effects on the flowering time and leaf numbers using photo-thermal model. Findings revealed a curvilinear response of flowering time to temperatures that is plants flowered after 34 (31.8°C), 35 (25.3°C), 37 (23.1°C), 43 (19.5°C) and 68 days (14.6°C) of transplantation in 2002 whereas in 2003 flowering time was recorded as 30 (31.5°C), 29 (27.5°C), 34 (24°C), 39 (22.5°C) and 67 days (15.1°C). Similarly, rate of progress to flower per day was increased linearly up to plateau at 28°C set-point temperature, thereafter, no changes in rate of progress to flower is observed which indicated that 28°C is the ceiling temperature for the flower initiation and development of cultivar Chimes White. A three to six days difference in flowering time was observed below ceiling temperature which might be due to the difference between the light integrals (0.9 MJ.m-2.d-1) in two years. Non-significant difference was observed regarding leaf numbers data in both years i.e. 9-10 leaves in 2002 and 8-9 leaves in 2003. Predicted data estimated from the photo-thermal model plotted against the actual data which showed a best fit, hence, the model application is validated which would assist growers to use it for plant scheduling. © 2015, Pakistan Botanical Society. All rights reserved. Source

Li B.,Chinese Academy of Agricultural Sciences | Cao X.,Chinese Academy of Agricultural Sciences | Cao X.,Chinese Academy of Sciences | Chen L.,Ningxia Entry Exit Inspection and Quarantine Bureau | And 8 more authors.
Plant Disease | Year: 2013

Blumeria graminis f. sp. tritici, the pathogen that causes wheat powdery mildew, can oversummer as mycelia or conidia on leaves of volunteer wheat plants in cool mountainous areas in China. In this study, the regions in China where B. graminis f. sp. tritici can oversummer were identified on the basis of the probability that temperature remains below a critical temperature that is lethal to B. graminis f. sp. tritici. Two methods, one describing the relationship between the average temperature (20 to 26°C) in a given continuous 10-day period and wheat powdery mildew severity, the other describing the relationship between the average temperature (26 to 33°C) and the number of lethal days on powdery mildew development, were used to calculate the oversummering probability using weather data for 743 sites across China. Spatial interpolation based on the ordinary kriging method was conducted for the regions without observation. Oversummering probability values were similar for most locations estimated between the two methods. The B. graminis f. sp. tritici oversummering regions in China were identified to be in mountainous or high-elevation areas, including most regions of Yunnan, west and central areas of Guizhou, south and northwest Sichuan, south and east Gansu, south Ningxia, north and west Shaanxi, central-north Shanxi, west Henan and Hubei, and some regions in Qinghai, Tibet, and Xinjiang. When the oversummering sites from this study were compared with observed survey data for some of these sites, about 90% of sites where B. graminis f. sp. tritici oversummering was observed had been found suitable by both methods. The coincidence frequency and the area under the receiver operating characteristic curve for model 2 were higher, albeit only slightly, than those for model 1. Thus, both methods may be used to assist in disease management and further investigation on pathogen oversummering. © 2013 The American Phytopathological Society. Source

Pettitt T.R.,Horticulture Research International | Wainwright M.F.,Horticulture Research International | Wakeham A.J.,Warwick HRI | Wakeham A.J.,University of Worcester | White J.G.,Warwick HRI
Plant Pathology | Year: 2011

A detached leaf assay was developed to determine the pathogenicity of Pythium isolates to cut-flower chrysanthemum roots. Leaves from young plants were excised and inoculated by insertion of a plug of mycelium into a slit cut in the excised petiole. After incubation leaves were assessed for presence and extent of necrosis. Necrosis indicated pathogenicity and was consistently confirmed by comparisons with whole plant inoculations. The rate of necrosis spread also gave some indication of virulence. Isolates of Pythium sylvaticum, P. ultimum and HS group were the most virulent, with a mean rate of spread of 14·6mm per day, significantly (P<0·05) faster than the mean rate of spread, 1·6mm per day, of less virulent isolates. Less virulent isolates included P. irregulare, P. oligandrum and P. aphanidermatum. The latter was unexpected, as P. aphanidermatum is an important species in pythium root rot epidemics in chrysanthemums elsewhere. The value of the detached leaf assay for screening large numbers of isolates was demonstrated in a survey of isolates from clinic samples from chrysanthemum nurseries and in a series of dilution-plating experiments looking at numbers of Pythium propagules in commercial chrysanthemum beds showing root rot. In the survey, the predominant pathogenic species was identified as P. sylvaticum and the most likely source of infection was contaminated soil as opposed to blocking media or irrigation water, whilst in soil colonization studies the use of detached leaf assays demonstrated a relationship between pathogenic inoculum concentration in soil and the expression of root rot symptoms. © 2011 The Authors. Plant Pathology © 2011 BSPP. Source

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