Weed seedbank responses to 12 years of applications of composts,animal slurries or mineral fertilisers     

B DE CAUWER  K VAN DEN BERGE  M COUGNON  R BULCKE  D REHEUL 《Weed Research》2010,50(5):425-435

  相似文献   

Prediction of codling moth egg hatch in Germany and Italy using the Californian forecasting model Bugoff21     

N. BLAGO  E. DE BERARDINIS 《EPPO Bulletin》1991,21(3):407-414

The effectiveness of the Californian model Bugoff2 for Cydia pomonella was tested in Germany (4 years) and Italy (2 years), the Italian results confirming the German findings. In the first codling moth generation (air temperatures normally below 30 C) good agreement was found between field observations of egg hatching and the model's forecast. However, the model gave notable differences for the second generation, i.e. 3 weeks in Germany and 1 week in Italy, and a significant difference for the third generation in Italy. These divergencies arise from an overestimation of the development rate of the codling moth in Bugoff 2's heat unit table whenever air temperature exceeds the upper limit for development. As a result of modifications to Bugoff 2, an example of a better simulation of the codling moth egg hatch in Germany and Italy is discussed.  相似文献   

Detection of potato virus Y in early-harvested potato tubers by cDNA hybridization and three modifications of ELISA1     

J. A. DE BOKX  C. CUPERUS 《EPPO Bulletin》1987,17(1):73-79

The standard ELISA method for detection of PVY in dormant potato tubers was compared with recently developed methods: (1) a hybridization technique, using a complementary DNA-probe to PVY^N; (2) three modifications of ELISA (standard monoclonal, Flegg & Clark polyclonal or monoclonal). Sap of six Dutch cultivars secondarily infected with PVY was subjected to these methods directly after lifting and after six subsequent one-week intervals during storage at 20°C. During storage the detectability of PVY decreased, irrespective of the diagnostic method applied. However, decrease was less in susceptible than in resistant cultivars. Although the hybridization technique yielded slightly better results than the standard ELISA procedure, it was time-consuming and involved hazardous reagents. The modifications of ELISA investigated were not, in general, more sensitive than standard ELISA.  相似文献   

3. Determination of the sensitivity of Phytophthora infestans to phenylamides: a semi-quantitative test method     

C. NUNINGER†  N. BOLTON  J. J. DE  WIJS† T. STAUB† 《EPPO Bulletin》1992,22(2):309-311

  相似文献   

Induced resistance in host mixtures and its effect on disease control in computer-simulated epidemics     

C. LANNOU  C. DE  VALLAVIEILLE-POPE H. GOYEAU 《Plant pathology》1995,44(3):478-489

The epidemic simulator EPIMUL was modified and used to study how induced resistance affected the development of epidemics in host mixtures. In the model, induced resistance resulted from the interaction of host tissue with avirulent spores and caused a reduction in the efficacy of virulent spores deposited afterwards. We denned three parameters to describe induced resistance: the level of protection, defined as the magnitude of reduction in the virulent spore efficacy for infecting host tissue; the host surface area protected by an interaction with one avirulent spore; and the duration of protection of the host tissue, in days. In our simulations, induced resistance slowed the epidemics and gave better disease control in the mixtures, even if protection lasted for only 2 days. The disease reduction in the mixture attributable to induced resistance was approximately proportional to the level of protection. The effect of induced resistance increased as the protected area increased. Epidemics were virtually unaffected by induced resistance restricted to the infection site, but the effect of induced resistance initially increased rapidly as larger areas were protected. There was little further gain as the protected area increased from 2·6% to 26%. The influence of induced resistance was reduced when the interactions between virulent and avirulent pathogens were reduced.  相似文献   

Biological control of Fusarium oxysporum f. sp. lycopersici     

A. DE  CAL  S. PASCUAL  I. LARENA  P. MELGAREJO 《Plant pathology》1995,44(5):909-917

Fungi known to produce lytic enzymes were used in an attempt to control wilt of tomato caused by Fusarium oxysporum f. sp. lycopersici (FOL). Some of the fungal species (Penicillium oxalicum, Penicillium purpurogenum and Aspergillus nidulans) damaged hyphae of FOL in vitro and reduced the numbers of microconidia in the soil. Treatments with fungi did not result in a reduction in either chlamydospores of FOL in soil or populations of FOL in the rhizosphere of tomato. P. oxalicum was the most effective agent of biocontrol, and it reduced disease severity in both non-autoclaved (20% decrease) and sterile soil. In sterile soil, P. oxalicum reduced disease with different levels of severity (27% decrease at high levels and 50% decrease at low levels). Disease control by A. nidulans and P purpurogenum was only achieved when disease severity was low in sterile soil (55% and 45%, respectively).  相似文献   

Biological diversity of citrus tristeza virus (CTV) isolates in Spain   总被引：5，自引：1，他引：5  

J. F. BALLESTER-OLMOS  J. A. PINA  E. A. CARBONELL  P. MORENO  A. HERMOSO DE  MENDOZA  M. CAMBRA  L. NAVARRO 《Plant pathology》1993,42(2):219-229

A survey of citrus tristeza virus (CTV) isolates was carried out in most citrus-growing areas in Spain. Twenty-two isolates were selected by geographical origin, cultivar of source tree, and symptoms observed on the host or in preliminary tests, and were biologically characterized.
A wide range of variation in transmissibility by aphids and symptom intensity on nine different indicator species or scion-rootstock combinations was observed among CTV isolates. Mexican lime. Citrus macrophylla , and to a lesser extent citron were the most useful hosts for characterizing these isolates, and leaf symptoms and stem pitting were the most discriminating traits. Positive correlation was observed between symptoms induced on Mexican lime and C. macrophylla , but not between the symptoms induced on these indicators under greenhouse conditions and the homologous symptoms on plants grown in the screenhouse. Some of the traits studied enabled us to establish relatively well-defined groups of isolates, but in most cases a continuous range of variation was obtained and no clear group could be defined.  相似文献   

Windborne spread of ergot disease (Claviceps africana) in sorghum A-lines in Zimbabwe     

D. E. FREDERICKSON  P. G. MANTLE  W. A. J. DE  MILLIANO 《Plant pathology》1993,42(3):368-377

Ergot disease spread rapidly in Zimbabwe amongst replicated plots of male-sterile sorghum A-lines, from a group of centrally situated and precociously inoculated plants. Prominent secondary conidiation by the pathogen, Claviceps africana , on the surface of exuded honeydew provided airborne spores which were trapped in a Burkard continuous spore trap and showed diurnal peaks of concentration in air close to the primary source of inoculum. The rate of disease spread ( r =0·2; range 0·14–0·58) closely matched that recorded for other plant pathogens such as Phytophthora infestans and Puccinia graminis tritici , and it is concluded that the characteristic secondary conidia of C. africana were the principal epidemiological agents within the experimental area. Ergot spread by windborne secondary conidia has significant epidemiological and economic implications for sorghum hybrid breeding in southern Africa.  相似文献   

Racial diversity and complexity in regional populations of Erysiphe graminis f.sp. hordei in France over a 5-year period   总被引：2，自引：3，他引：2  

D. ANDRIVON  C. DE  VALLAVIEILLE-POPE 《Plant pathology》1993,42(3):443-464

The evolution of race patterns in three French regional populations of the barley powdery mildew pathogen Erysiphe graminis f.sp. hordei over a 5-year period showed rapid adaptation to newly introduced host resistance genes. In all three regions, the main change consisted of the replacement of initially abundant races by pathotypes differing markedly from them by their virulence gene combinations. This explained the increase in diversity during the first 3 years of the survey, when the second group of pathotypes became more common in the populations, and its subsequent decrease due to the decline of the first group of races. The mean number of virulence genes per isolate did not vary noticeably over time in the three populations, remaining at about four out of 12 genes tested. However, the distribution of the isolates into virulence complexity classes was greatly modified, fitting a binomial distribution by the end of the study, although significant deviations were apparent in the first 2 years (1986 and 1987). The data indicate that selection, migration and recombination are the most important factors shaping race structure and evolution in powdery mildew populations, and that mutation is of limited significance. No convincing evidence was obtained for the existence of stabilizing selection sensu Vanderplank as the mechanism limiting virulence complexity. Implications regarding spatial and temporal deployment of race-specific resistance genes to control powdery mildew are discussed.  相似文献   

Farmer record of pregnancy status pre-slaughter compared with actual pregnancy status post-slaughter and prevalence of gross genital tract abnormalities in New Zealand dairy cows     

Lawton DE  Mead FM  Baldwin RR 《New Zealand veterinary journal》2000,48(6):160-165

AIMS: To record the prevalence of gross abnormalities of the reproductive tract in culled New Zealand dairy cows, to determine how accurately farmers classify the pregnancy status of their animals and to establish if this was influenced by method of pregnancy diagnosis. METHODS: The reproductive tracts from 1134 cull dairy cows were examined after slaughter and evisceration for the presence of gross abnormalities, ovarian activity and pregnancy at a commercial abattoir. The farmers that had submitted these animals for slaughter were surveyed for information about the farm and herd from which each cow was derived and to establish whether the farmer believed each cow to be pregnant or not. The method that had been used to determine pregnancy status was recorded for each animal. RESULTS: Gross abnormalities were evident in 5.7% of reproductive tracts. Ovarian activity (presence of follicles 5 mm diameter and/or a corpus luteum) was apparent in 88% of non-pregnant cows. Pregnancy was detected in 39% of cows, of which 2.3% carried twins. The pregnancy status evident at slaughter varied from that reported by farmers in 7.0% of the 954 cows for which farmers were able to provide information. Of the cows that had been examined by palpation or ultrasound per rectum prior to slaughter, 10.3% that were recorded as non-pregnant by farmers were pregnant, and 3.2% of those recorded as pregnant were not. Of the cows that had not been examined, 3.8% of those recorded as nonpregnant by farmers were pregnant while 10.4% of those recorded as pregnant were not. There was no apparent association between gross genital tract abnormalities or ovarian activity and the misclassification of pregnancy status. Amongst cows that were pregnant at slaughter the foetus was significantly smaller in cows that had been recorded as 'not pregnant' after palpation or ultrasound examination than in cows that had been recorded as 'not pregnant' on the basis of farmer observation only. CONCLUSIONS: The prevalence of gross abnormalities of the reproductive tract was comparable to that reported in similar studies overseas. Farmer observation as a method of pregnancy detection overestimates pregnancy rate. Pregnancy status may be misclassified or misrecorded following palpation or ultrasound examination of cattle per rectum. Accurate classification of pregnancy status is dependent on the method and timing of pregnancy diagnosis and on minimising errors of diagnosis, cow identification and recording.  相似文献