Study of Resistance to Orobanche ramosa in Host (Oilseed Rape and Carrot) and Non-host (Maize) Plants

Orobanche ramosa is a parasitic Angiosperm responsible for severe yield losses in several economical crops. It is a serious threat in oilseed rape in France and Morocco and is appearing in carrot crops in Morocco. In this study, several varieties of oilseed rape and carrot were screened in order to identify resistant cultivars and to characterize the resistance mechanisms involved. All the 15 oilseed rape varieties tested were susceptible. In carrot, the varieties 'Colmar à coeur rouge' and 'Nantaise demi-longue' were susceptible, whereas 'Palaiseau' and 'Buror' were resistant. In the susceptible 'Colmar à coeur rouge' carrot no defence reactions were found and the development of the parasite inhibited carrot tap root formation. In the resistant carrot varieties, the parasite germinated, became attached to the host root but became necrotic before emergence. In 'Buror' carrot, formation of a mechanical barrier was associated with the restriction to the cortex of the parasite. In maize cv. 'Vigni', a non-host of O. ramosa, thickening of xylem vessels, cell divisions in the central cylinder and formation of an encapsulation layer were observed in association with restricted development of Orobanche haustoria.     

The Eurotiomycete <Emphasis Type="Italic">Apinisia graminicola</Emphasis> as the causal agent of a leaf spot disease on the energy crop <Emphasis Type="Italic">Miscanthus</Emphasis> x <Emphasis Type="Italic">giganteus</Emphasis> in Northern Germany

Miscanthus x giganteus is a fast growing, perennial energy crop for temperate climates. Because of its high annual biomass production rates and its characteristics as a low-input crop, an expansion of field cultivation can be anticipated to cover increasing demands for sustainable biomass production. However, knowledge about pathogens that could have an impact on biomass production is still limited for M. giganteus. Here, we report about the isolation of the filamentous fungus Apinisia graminicola from necrotic leaf lesions of M. giganteus grown on a field trial plot in Northern Germany. Inoculation assays with the isolated A. graminicola strain confirmed its capacity to cause a leaf spot disease on M. giganteus. Additional inoculation assays revealed that A. graminicola also caused necrotic lesions on leaves of the model grass Brachypodium distachyon. Generally, symptoms of A. graminicola-caused leaf spot disease were stronger on B. distachyon compared to M. giganteus. Incubation temperatures above 22 °C during A. graminicola infection resulted in stronger disease symptoms on both, M. giganteus and B. distachyon leaves. Microscopic analysis of cross sectioned, infected leaf tissue revealed an epiphytic mycelium formation on the surface and an endophytic colonization of the mesophyll leave tissue, especially in M. giganteus. Our results revealed that the isolated A. graminicola strain is a causal agent of a leaf spot disease on grass leaves. Its potential on endophytic growth in M. giganteus might open new possibilities in studying this type of plant-fungal interaction on a cellular and molecular level in an energy crop.     

Plasma renin activity and plasma concentrations of aldosterone, cortisol, adrenocorticotropic hormone, and alpha-melanocyte-stimulating hormone in healthy cats

A pathogenetic role of the renin-angiotensin-aldosterone system has been implicated in cats in both systemic arterial hypertension and hypokalemic myopathy. Yet, measurement of plasma aldosterone concentrations (PACs) and plasma renin activity (PRA) has not unequivocally pointed to hyperaldosteronism as a cause of these conditions. To obtain appropriate reference ranges, this study included a large number (130) of healthy house cats of different breeds without a history of recent illness and plasma concentrations of urea and creatinine below the upper limit of the respective reference ranges. In addition, the pituitary-adrenocortical axis was studied by measuring plasma concentrations of adrenocorticotropic hormone (ACTH), alpha-melanocyte-stimulating hormone (alpha-MSH), and cortisol. Reference ranges for PACs (110-540 pmol/L; 40-195 pg/mL), PRA (60-630 fmol/L/s; 0.3-3 ng/mL/h), and the aldosterone to renin ratio (ARR) (0.3-3.8) were very similar to those established in the same laboratory for humans in a supine position. No breed differences were found. The ARRs in neutered cats were significantly higher than in intact cats, primarily because of low PRA in neutered cats. The ARRs of cats > or = 5 years of age were significantly higher than those of cats < 5 years of age. The plasma concentrations of ACTH, alpha-MSH, and cortisol did not correlate significantly with PAC. Thus, although blood sampling was performed in cats in nonstandardized positions and was associated with a wide variation of stress responses, the references ranges of PAC, PRA, and ARR were similar to the relatively narrow limits established for humans under standardized conditions. The effects of neutering and aging on PRA and ARR warrant further investigation.     

Evaluation of a single dose versus a divided dose regimen of danofloxacin in treatment of Actinobacillus pleuropneumoniae infection in pigs

A single versus a divided dose regimen of danofloxacin was evaluated in treatment of porcine Actinobacillus pleuropneumoniae infection using clinical observations combined with biochemical infection markers: C-reactive protein, zinc and ascorbic acid. Twenty hours after experimental infection, the 18 pigs received danofloxacin intravenously as a single dose of 2.5mg/kg or four doses of 0.6 mg/kg administered at 24h intervals. These dosage regimens resulted in similar AUCs of the plasma danofloxacin vs time curve. The maximum concentration was 3.5-fold higher using the single dose regimen, while the time with concentrations above the MIC was 2.5-fold longer using the fractionated regimen. Using the single dose regimen, temperature was normalised 32 h post-infection. In contrast, normalisation was delayed until 44 h post-infection using four low doses and a relapse with elevated temperatures at 52 and 68 h was observed. No other significant differences between the treatments were found, neither regarding clinical, haematological nor biochemical observations. The use of the more convenient single dose regimen was appropriate, as it was at least equivalent to the fractionated regimen.     

Real-time polymerase chain reaction testing for the detection of Mycobacterium genavense and Mycobacterium avium complex species in avian samples

Diagnosis of avian mycobacteriosis, caused by Mycobacterium genavense or species belonging to the Mycobacterium avium complex (MAC), is problematic. Polymerase chain reaction (PCR) offers rapid and sensitive detection of minute quantities of DNA, and conventional protocols have been used for evaluating avian specimens. The recent development of real-time PCR offers several advantages over conventional PCR. In attempts to improve diagnosing avian mycobacteriosis, a real-time TaqMan PCR assay was developed targeting the 65-kD heat shock protein gene of M. genavense and MAC spp. Nineteen reference isolates, 16 clinical isolates, and 32 avian tissue samples were used to evaluate the assay. When sufficient amplicons were produced, the species of mycobacteria was determined by standard sequencing of TaqMan PCR products and compared with results from commercial mycobacteriology laboratories and/or standard sequencing of conventional PCR products. The TaqMan PCR detected DNA from reference isolates of M. genavense, MAC spp., and Mycobacterium tuberculosis complex spp. Of the clinical isolates, the TaqMan PCR detected DNA from 10 of 12 Mycobacterium avium avium isolates and two of three Mycobacterium avium intracellulare isolates. For the tissue samples, the TaqMan PCR amplified DNA in six of nine samples that were identified by sequencing of conventional PCR products and/or by commercial mycobacteriology laboratories as being MAC spp. positive and three of four samples that were positive for M. genavense. There was some disagreement between speciation results from the TaqMan PCR and those from commercial mycobacteriology laboratories or conventional PCR or both. This disagreement was suspected to be because of relatively small numbers of base pairs in the TaqMan PCR products. The TaqMan PCR may provide a useful tool for evaluating clinical samples for DNA from mycobacteria species that most commonly infect birds; however, further refinement is needed in order to improve sensitivity and provide more accurate speciation.     

塔里木河下游阿拉干断面胡杨林空间分布特征及其影响因素

通过小尺度生态监测与遥感数据分析获取塔里木河下游荒漠河岸林现状信息,集中对阿拉干断面设立的100hm2长期监测样方内的胡杨树进行了详细的调查,对该断面胡杨林空间分布特征及其影响因素进行了分析。研究结果表明：塔里木河下游的胡杨具有伴河生长的特性;随着离河距离的增加,胡杨株数呈递减趋势;大部分胡杨主要分布在离河道200m范...     

Possible Root Infection of Cercospora beticola in Sugar Beet

A potential primary infection site of the foliar pathogen Cercospora beticola in sugar beet is described. Sugar beet seedlings of the susceptible cv. Auris were grown in a standard soil for 14 days. A monoconidial culture of a C. beticola isolate was grown to produce conidia. In experiment 1, roots were immersed in a conidial suspension of isolate code IRS 00-4, or in tap water (control), for 2 days. After incubation seedlings were potted in a peat – fine river sand mixture and placed at low relative humidity (RH) (<80%) or high RH (100%). Twelve days after infection, seedlings at high RH showed more disease incidence (90%) than seedlings grown at low RH (disease incidence = 25%), whereas no disease symptoms developed in the control seedlings. Cercospora leaf spots (CLSs) developed on the cotyledons, leaves, petioles and stems of the seedlings. In experiment 2, roots were immersed in a conidial suspension of isolate code IRS 00-2 for 5 h. Thirty-four days after infection at high RH, 100% disease incidence was observed in the treated seedlings and one CLS in the control treatment. First indications of leaf spot development were observed as reddish purple discolouration of individual parenchymatic cells. Because splash dispersal and symptoms due to infested soil were excluded, we showed that it is possible to obtain CLS symptoms in sugar beet seedlings when their roots were immersed in conidial suspensions of C. beticola, thus demonstrating that roots can be a primary infection site.     

Evaluation of foliar resistance in potato to Phytophthora infestans based on an international field trial network

During the period 2000–03, local potato cultivars in Estonia, Latvia, Lithuania, Poland and Denmark were tested for foliar resistance to Phytophthora infestans (late blight) in an international field trial network. Four standard cultivars were included in the trials: Sava, Oleva, Danva and Kuras. Primary disease-assessment data were entered into a common database, and parameters from the disease progress curves were calculated and made available on interactive web pages. A regression model, using relative area under disease progress curve (RAUDPC) values for cv. Oleva as a reference, was developed for the estimation of 1–9 scale values, where 1 = most susceptible. Standard deviations for the estimated 1–9 scale values and a nonparametric rank stability analysis of RAUDPC were used to evaluate the stability of resistance of the cultivars. Overall, the results showed stability of resistance for cvs Sava, Oleva and Danva, but not for Kuras. Use of the Internet-based Web-Blight service in this study facilitated comparison of results among countries for the level and stability of resistance. The estimated 1–9 scale values were similar to, or slightly lower than, those from official cultivar lists or from the European Cultivated Potato Database, especially for the more resistant cultivars. Possible reasons for discrepancies from different sources and locations are discussed. It is concluded that RAUPDC and the derived 1–9 scale values are useful for ranking cultivars for resistance to P. infestans , but this information is not detailed enough for use in a decision support system for late blight control.     

Untersuchungen zur ökologischen situation ostdeutscher landwirtschaftsbetriebe

Repräsentative ostdeutsche Landwirtschaftsbetriebe sind hinsichtlich ihrer Umweltverträglichkeit bewertet worden. Dazu diente eine Methode, die für ca. 30 relevante Umwelt‐Gefährdungspotentiale aus den Bereichen Düngung, Bodenschutz, Pflanzenschutzmitteleinsatz, Agrarraumgestaltung, Artendiversität, Energiebilanz und Tierbesatz kritische Umweltbelastungen formuliert und damit aktuelle Betriebsdaten wertend vergleicht.

Die Ergebnisse zeigen eine sehr differenzierte Situation. Während Stoffbelastungen mit Konsequenzen für die Nahrungsqualität weitgehend unkritisch sind, bestehen Defizite vor allem als “Altlasten”; in den Bereichen Bodenschutz und Agrarraumgestaltung.

Beziehungen zwischen Intensität und Umweltverträglichkeitsbewertung werden diskutiert.