The Use of a GUS Transformant of Trichoderma Harzianum, Strain T3a, to Study Metabolic Activity in the Spermosphere and Rhizosphere Related to Biocontrol of Pythium Damping-off And Root Rot     

Helge Green  Nina Heiberg  Kirsten Lejbølle  Dan Funck Jensen 《European journal of plant pathology / European Foundation for Plant Pathology》2001,107(3):349-359

The activity of Trichoderma harzianum in the spermosphere and rhizosphere of different plant species was studied by use of a beta-glucuronidase (GUS) transformant (strain T3a). Hereby, direct observation of micro-habitats supporting metabolic activity of T. harzianum is reported. Germination of conidia and mycelial growth were not supported by exudates from healthy roots of various ages. Instead, growth and activity of T. harzianum depended on access to dead organic substrates such as seed coats, decaying roots, and wounds, including those caused by infecting pathogens. A correlation between the GUS activity of T. harzianum and the biomass of Pythium ultimum in infected roots was established. On the basis of our observations, we suggest that the biocontrol ability of T. harzianum involves competition with the pathogen for substrates including the seed coat, and wounded or infected root tissue.  相似文献   

Effects of photoperiod on sex steroids and gonad maturation in Arctic charr     

Marianne Frantzen  Arne M. Arnesen  Brge Damsgrd  Helge Tveiten  Helge K. Johnsen 《Aquaculture (Amsterdam, Netherlands)》2004,240(1-4):561-574

Four groups of Arctic charr (age 3+), previously exposed to natural photoperiod, were subjected to different photoperiod regimes from February 20: Simulated natural photoperiod (SNP; Tromsø 70°N), continuous light (LD 24:0) followed by short day (LD 6:18) from either May 1 (L_Feb–May) or June 25 (L_Feb–June), or continuous light (LD 24:0) throughout the experiment (L_Continuous). In females, peak levels of estradiol-17β and testosterone were 6 and 10, 6 and 7, and 3 and 5 weeks advanced, in L_Feb–May, L_Feb–June and L_Continuous, respectively, whereas in males plasma levels of 11-ketotestosterone peaked 8 weeks earlier in L_Feb–May and L_Feb–June than in SNP and L_Continuous. Median ovulation time in L_Feb–May and L_Feb–June was advanced by 10 weeks compared to SNP and L_Continuous, and median spermiation time (first observation of running milt in each individual) in L_Feb–May, L_Feb–June and L_Continuous was advanced by 10, 7 and 5 weeks, compared to SNP. A switch from long to short day early in the reproductive cycle (L_Feb–May and L_Feb–June) apparently resulted in stronger synchronization of both ovulation and spermiation. Ovulation in L_Feb–May and L_Feb–June occurred over 3 weeks (L_Feb–May) and 8 weeks (L_Feb–June), as compared to 10 weeks in the SNP group, whereas all males (except one individual) began spermiating over a period of 3 weeks (L_Feb–June), or less (L_Feb–May), as compared to 7 weeks in the SNP group. Lack of a short day stimulus (L_Continuous), on the other hand, resulted in larger variation in the timing of final maturation, with ovulation and spermiation being spread over 15 weeks. Low egg survival in L_Feb–May (17% versus 60% and 97% for L_Continuous and SNP) indicate that a long day signal of 10 weeks early in the reproductive cycle may be too short to ensure good egg and sperm quality. Photoperiod manipulation did not affect the proportion of maturing fish.  相似文献   

Automated image analysis as a tool to quantify the colour and composition of rainbow trout (Oncorhynchus mykiss W.) cutlets     

Lars Helge Stien  Fredrik Manne  Antti Kause  Anders Kiessling 《Aquaculture (Amsterdam, Netherlands)》2006,261(2):695-705

The goal of this paper is to propose and evaluate automated image analysis methods for describing muscle cutlets in rainbow trout. The proposed automated image analysis methods were tested on a total of 983 scanned images of trout cutlets, and included quality traits such as fat percentage, flesh colour and the size of morphologically distinguishable subparts of the cutlet. A sub-sample of 50 images was randomly selected for manual segmentation of the cutlet, the dorsal fat depot and the red muscle and regions. The identification of these regions by manual and automatic image analysis correlated strongly (r = 0.97, r = 0.95 and r = 0.91, respectively). The estimated fat percentage obtained from image analysis, based on the area of visible fat and the colour of the cutlet flesh, correlated well with chemical fat percentage measured by mid-infrared transmission spectroscopy (MIT) (r = 0.78). The automated image analysis methods are therefore a reliable means of predicting the fat percentage of trout cutlets. Principal component analysis (PCA) loading plots were used to identify subsets of variables from the image analysis of special significance for further studies; cutlet area, dorsal fat depot area, red muscle area, back height, cutlet width, and width of left and right abdomen wall were among the variables selected. PCA loading plots of different colour variables indicated that simple statistical coefficients such as percentiles and mean values can be used to quantify different aspects of flesh colour. In conclusion, the methods presented here provide a powerful toolbox for describing important morphological structures and quality traits of trout cutlets.  相似文献   

Interactions between the external mycelium of the mycorrhizal fungus Glomus intraradices and other soil microorganisms as affected by organic matter     

Annierose Albertsen  Helge Green  John Larsen 《Soil biology & biochemistry》2006,38(5):1008-1014

The influence of organic matter on the interactions between external mycelium of the arbuscular mycorrhizal (AM) fungus Glomus intraradices, the bacterium Burkholderia cepacia and other soil microorganisms was studied in a root-free sand environment. Organic matter amendment, in terms of ground barley leaves, markedly increased the growth of the external mycelium of G. intraradices as estimated both with the fatty acid biomarker 16:1ω5 and hyphal length measurements. Mycelial proliferation of G. intraradices in sand with organic matter was unaffected by both inoculation with B. cepacia and a soil filtrate containing a mixed population of indigenous microorganisms. On the other hand, in the absence of organic matter, both inoculation with B. cepacia and the soil filtrate reduced the growth of G. intraradices, as estimated with measurements of 16:1ω5. In contrast, B. cepacia inoculation increased hyphal length density of G. intraradices in the absence of organic matter. Overall, the presence of external mycelium of G. intraradices increased the bacterial biomass and counteracted a suppressive effect of B. cepacia on the growth of saprotrophic fungi.  相似文献   

Synthesis of the sednet work package 5 outcomes     

Susanne Heise  Sabine E. Apitz  Marc Babut  Helge Bergmann  Piet den Besten  Gerald J. Ellen  Jan Joziasse  Alexandra Katsiri  Vera Maaß  Amy Oen  Adriaan Slob  Sue White 《Journal of Soils and Sediments》2004,4(4):233-235

  相似文献   

策勒沙漠-绿洲过渡带土壤种子库的基本特征   总被引：2，自引：0，他引：2  

马坚  杨远昭  李利  王纯利  张希明 《新疆农业大学学报》2007,30(3):53-59

通过室外萌发法对策勒沙漠-绿洲过渡带土壤种子库的研究发现:该区域土壤中活性种子从总储量上来看较为丰富,其中有12种植物,分属8科,但各植物种的种子数量分配极不均匀,仅有多枝柽柳的种子数量丰富,其它植物种的土壤种子储量相对匮乏,甚至严重匮乏;种子库的生活型组成以多年生草本占优(53.85%),一年生草本植物次之(30.77%);不同群落与地貌类型的种子库间保持着较高的相似性。  相似文献   

EMS and UV irradiation induce unstable resistance against CAA fungicides in <Emphasis Type="Italic">Bremia lactucae</Emphasis>     

Avia E. Rubin  Ayelet-Chen Werdiger  Mathias Blum  Ulrich Gisi  Helge Sierotzki  Dietrich Hermann  Yigal Cohen 《European journal of plant pathology / European Foundation for Plant Pathology》2011,129(2):339-351

Wild type (WT) field isolates of Bremia lactucae failed to germinate in vitro or infect lettuce leaves in the presence of CAA (carboxylic acid amide) fungicides. Minimal inhibitory concentrations (MIC) for mandipropamid, dimethomorph, benthiavalicarb and iprovalicarb were 0.005, 0.5, 0.5 and 5 μg ml⁻¹, respectively. Mutagenesis experiments showed that spores exposed to EMS (ethyl methane sulphonate) or UV irradiation (254 nm) could infect lettuce leaves in the presence of up to 100 μg ml⁻¹ CAA. The proportion of infected leaves relative to the number of spores inoculated (infection frequency) was inversely related to the concentration of CAA used, ranging between 0 and 160 per 1 × 10⁶ spores. Resistant mutants (RM) lost their resistance within 1–14 reproduction cycles on CAA-treated plants. Crosses were made between RMxWT isolates and RMxRM isolates with an attempt to obtain stable homozygous resistant off-springs. Such crosses yielded few resistant but unstable progeny isolates. Mutagenic treatments given to hybrid isolates also failed to produce stable resistance. Previous gene sequencing data showed that stable resistance to CAAs is based on a single SNP in the cellulose synthase 3 (CesA3) gene of Plasmopara viticola. Therefore, we sequenced a 582 bp DNA fragment of Ces3A of WT, RM and hybrid isolates of B.lactucae. No mutation in this gene fragment was found. We conclude that mutagenic agents like EMS or UV may induce resistance to CAA in Bremia lactucae but this resistance is not stable and not linked to mutations in CesA3 gene.  相似文献   

Resistance mechanism to carboxylic acid amide fungicides in the cucurbit downy mildew pathogen Pseudoperonospora cubensis     

Blum M  Waldner M  Olaya G  Cohen Y  Gisi U  Sierotzki H 《Pest management science》2011,67(10):1211-1214

BACKGROUND: Pseudoperonospora cubensis, the causal oomycete agent of cucurbit downy mildew, is responsible for enormous crop losses in many species of Cucurbitaceae, particularly in cucumber and melon. Disease control is mainly achieved by combinations of host resistance and fungicide applications. However, since 2004, resistance to downy mildew in cucumber has been overcome by the pathogen, thus driving farmers to rely only on fungicide spray applications, including carboxylic acid amide (CAA) fungicides. Recently, CAA‐resistant isolates of P. cubensis were recovered, but the underlying mechanism of resistance was not revealed. The purpose of the present study was to identify the molecular mechanism controlling resistance to CAAs in P. cubensis. RESULTS: The four CesA (cellulose synthase) genes responsible for cellulose biosynthesis in P. cubensis were characterised. Resistant strains showed a mutation in the CesA3 gene, at position 1105, leading to an amino acid exchange from glycine to valine or tryptophan. Cross‐resistance tests with different CAAs indicated that these mutations lead to resistance against all tested CAAs. CONCLUSION: Point mutations in the CesA3 gene of P. cubensis lead to CAA resistance. Accurate monitoring of these mutations among P. cubensis populations may improve/facilitate adequate recommendation/deployment of fungicides in the field. Copyright © 2011 Society of Chemical Industry  相似文献   

Long term in situ measurements of gas exchange in a Norway spruce canopy at ambient and elevated ozone levels using a light weight chamber system — System designs and first results     

Teis N. Mikkelsen  Helge Ro-Poulsen 《Water, air, and soil pollution》1995,85(3):1413-1418

The gas exchange system is computer controlled and is designed to measure and control 14 temperature regulated chambers enclosing spruce twigs for several months with minimum ozone absorption. The system is mounted on sun exposed single year classes of a Norway spruce stand in western Jutland, Denmark. Since July 1994 the temperature control system has been in function. Results show that 95% of the temperature measurements inside the cuvettes are within the range ?2 to +3 °C of the ambient temperature. Gas exchange measurements show that the current year shoots have a higher net photosynthesis than the older shoots. The net photosynthesis in current year needles on sunny days is significantly reduced by the 6 h daily 30–40 ppb ozone addition.  相似文献   

Management of urban recreational woodlands: The case of Norway   总被引：1，自引：0，他引：1  

Vegard Gundersen  Lars Helge Frivold  Tor Myking  Bernt-Hvard yen 《Urban Forestry & Urban Greening》2006,5(2):73-82

A questionnaire was mailed to 351 forest supervisors in Norway about the condition and management of urban woodlands important for recreation. The overall respondense rate was 56% and included 29 large urban settlements (10,000 inhabitants) and 168 small urban settlements (200–9999 inhabitants), encompassing about 37% of the Norwegian population. The areas included in the survey cover 194,100 ha, i.e. 1.6% of the forested area. Urban woodlands were defined as the annually most frequently visited forest areas larger than 50 ha. The average size of urban woodlands was about 1000 ha, equal in large and small urban settlements. About 73% of the urban woodlands were closer than 500 m from settlements. The mean proportion of forest in the urban fringe was 40%. Like most forested land in Norway, urban woodlands were mainly privately owned. In large urban settlements the proportion of municipal forest was slightly higher than in small urban settlements. The distributions of forest stand age and tree species composition in urban woodlands did not deviate from the overall forest situation in the region. Silviculture and forest plans were prominent in urban woodlands around both large and small urban settlements, but special plans for recreation and conservation were equally rare. Recreational facilities and conflicts were most common in urban woodlands around large urban settlements. The effect of the recommendations on management of urban woodlands developed during the 1970s is questioned regarding the small differences between urban woodlands and the general forest situation, as well as between woodlands of large and small urban settlements. However, recreational efforts may have been more intensive in smaller neighbourhood woodlands of less than 50 ha, which were beyond the scope of this survey.  相似文献