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S. A. Selim K. M. S. Aziz A. J. Sarker H. Rahman 《Veterinary research communications》1991,15(4):327-333
Faecal samples from 434 calves under 1 year of age (307 diarrhoeal and 127 normal) were collected from three dairy farms and one village in selected areas of Bangladesh. The samples were tested by an enzyme-linked immunosorbent assay (ELISA) to detect the presence of rotavirus antigen. Of 402 dairy calves tested, 28 (7.0%) were positive, of which 21 (7.2%) were from diarrhoeic calves and 7 (6.3%) from non-diarrhoeic calves. Rotavirus infection varied from farm to farm (2.7–9.2%) and there was no positive response from any of the 32 village calves. Rotavirus was most commonly found in calves of 1 week of age or less (up to 22.2% in one group) but was not found in any calves later than 6 months of age. More than 80% of rotavirus-positive samples from diarrhoeic calves exhibited a titre of 128 or more (geometric mean 345±4.5), whereas non-diarrhoeal calves had titres less than or equal to 128 (geometric mean=29±1.9), suggesting that rotavirus infection in calves in Bangladesh was mostly associated with diarrhoea. 相似文献
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R. Pontzen H. Scheinpflug 《European journal of plant pathology / European Foundation for Plant Pathology》1989,95(1):151-160
With three plant pathogens,Botrytis cinerea, Venturia inaequalis and Puccinia graminis f. sp.tritici, the time course of sterol biosynthesis during spore germination was examined by labeling experiments along with the question whether this pathway could be inhibited by triazole fungicides. Conidia ofB. cinerea andV. inaequalis are able to synthesize sterols immediately after the beginning of the germination process when the germ tubes have not yet emerged. On the contrary uredospores ofP. graminis start sterol biosynthesis after 6 to 8 h germination time almost at the end of the germ tube phase, indicating that sterol reserves of the spores are likely to be used for the germ tube growth.The sterol C-14 demethylation appeared to be the rate limiting step within the sterol biosynthetic pathway: the half life of 24-methylenedihydrolanosterol was less than 1 h forB. cinerea. It was more than 1 h forV. inaequalis and 3 h forP. graminis. Independent of these differences in the time course of sterol biosynthesis and in the C-14 demethylation rate, the synthesis of sterols in germinating spores was strongly inhibited by triazole fungicides in all three pathogens examined. In contrast toP. graminis, this inhibition could be demonstrated withB. cinerea andV. inaequalis even in ungerminated conidia, indicating that the fungicides were rapidly taken up and reached their target within 1 or 2 h. These results are discussed along with the question whether spore germination can be used as a bioassay for the estimation of sensitivities of triazole fungicides. 相似文献
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C. Nuninger-Ney F. -J. Schwinn T. Staub 《European journal of plant pathology / European Foundation for Plant Pathology》1989,95(1):137-150
The inherent resistance risk forMonilinia fructicola against sterol-biosynthesis inhibitors (SBIs) was estimated inin vitro andin vivo laboratory studies. Several mutant strains were selected on media amended with the triazole fungicides penconazole, etaconazole or the morpholine fungicide fenpropimorph.The potential forM. fructicola to develop resistance to the triazoles or to the morpholines was similar.The level of resistance attained did not differ for the two classes of fungicides after a single cycle of treatment with nitrosoguanidine (NTG). Attemps to select mutants with a higher level of resistance to penconazole after successive mutagenic treatments were successful. Most of the mutants were less fit than wild-type strains. Mutants with a low level of resistance had an almost normal mycelial growth rate, whereas growth of mutants with a higher level of resistance was significantly reduced. Spore production was highest in the wild-type strains, similar to the latter in a few resistant strains and less in most others. Only one mutant with an intermediate level of resistance could successfully compete in a mixed population with a wild type strain during successive infection cycles on peaches. Resistance was not stable in highly resistant mutants. Cross resistance to the inhibitors of 14-methylsterol demethylation (DMIs) tested was confirmedin vitro andin vivo for all mutant strains. One DMI-resistant mutant was also resistant to fenpropimorph and two fenpropimorph-resistant mutants were resistant to penconazole. 相似文献
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H. D. Frinking R. Verweij 《European journal of plant pathology / European Foundation for Plant Pathology》1989,95(1):63-72
Colonization of rose by powdery mildew (Sphaerotheca pannosa) is described in terms of mycelium growth, conidiophore production and sporulation in time. The data used are gathered during different years, put together and treated by means of graphic models. Colonies could be separated into fast and slow growing colonies. Colonies initiated on leaves of increasing age showed a decreasing growth rate. Production of conidiophores and conidia started on the same day, and the relative activity of conidiophore production reached its maximum 6 days after the end of the latency period, followed 1 day later by the maximum activity of conidium production. Both conidiophore and conidium production continued for a long time at a low level. The effect of leaf age on conidiophore production found expression in differences in production rate during the first days of colony development and in final production levels. Observations on naturally infected leaves in an outdoor experiment showed a rapid decrease of sporulation on leaves of 10 days and older. Highest percentages of sporulating leaf area were observed on leaves between 7 and 10 days old. 相似文献
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G. J. Bollen D. Volker A. P. Wijnen 《European journal of plant pathology / European Foundation for Plant Pathology》1989,95(1):19-30
Samples of heavily infested crop residues were incorporated in static compost heaps (2.5–4.6 m3) of the Indore type. Temperature increased to 50–70°C within 6 days depending on the type of crop residues used and the location within the heap. The heat phase (>40 °C) lasted 2–3 weeks and was followed by a c. 5-months maturation phase (<40 °C). Among the 17 pathogens tested, onlyOlpidium brassicae and one of the four formae speciales ofFusarium oxysporum that were tested survived composting, but also their inoculum was greatly reduced.Survival during specific phases of composting was studied by incorporation and retrieval of samples at various stages of the process.F. oxysporum f. sp.melonis was completely inactivated andO. brassicae andPlasmodiophora brassicae were almost completely inactivated during the short heat phase. The three pathogens survived the long-lasting maturation phase without loss of viability. Heat evolved during composting was found to be the most important factor involved with sanitation of crop residues. The possible involvement of fungitoxic conversion products and microbial antagonism is discussed. 相似文献
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W. J. Blok G. J. Bollen 《European journal of plant pathology / European Foundation for Plant Pathology》1993,99(3):29-40
Replant disease is a common phenomenon in asparagus growing in the Netherlands. It is distinct from the decline phenomenon reported from many other asparagus producing area’s. The involvement of autotoxins from root residues of former asparagus crops was evaluated. Residues of aspar agus roots decompose extremely slowly. At two locations, each with fields where asparagus production was terminated 1 and 10 years before, biomass of root residues was 4180 and 11060 kg dw ha?1 after 1 year and 420 and 1140 kg dw ha?1 after 10 years.Although 10-year-old residues were for the greater part decomposed, crude aqueous extracts inhibited root growth of asparagus seedlings significantly and even more of garden cress. In root observation boxes with field soil mixed with non-sterilized or sterilized asparagus root fragments, growth of secondary roots was inhibited. Non-sterilized strawberry roots did not inhibit root growth, suggesting that effects of organic matter were not involved. In a pot experiment, sterilized asparagus root fragments inhibited root growth when added at a rate of 20 g1?1, but not a 2 g1?1 Addition of non-sterilized root fragments strongly inhibited root growth at both levels. This was probably due to simultaneous infection byFusarium oxysporum present in these residues. When an asparagus field is replanted, the amount of root residues left behind in soil after termination of the crop in the previous season is about 2 g dw 1?1, that corresponds to approx. 11000 kg dw ha?1. This level is too low for considering direct growth inhibition by autotoxins as a major factor. Their possible indirect effects are briefly discussed. 相似文献