Clove-transmissibility of <Emphasis Type="Italic">Pseudomonas salomonii</Emphasis>, the causal agent of ‘Café au lait’ disease of garlic     

Marie-Agnès Jacques  Nathaëlle Luçon  Sandrine Houdault 《European journal of plant pathology / European Foundation for Plant Pathology》2009,124(4):695-700

Bacterial blight of garlic, caused by Pseudomonas salomonii, results in leaf and sheath necrosis and sometimes leads to soft rot and plant death. The epidemiology of this bacterial disease, known as ‘Café au lait’ disease, is poorly understood and no resistant cultivars are currently available. To develop control strategies for this disease, we investigated principal sources of inoculum. The pathogen was isolated from bulbs from plants with typical vegetative symptoms of bacterial blight. Subsequent development of typical foliar symptoms on plantlets originating from symptomatic bulbs demonstrated transmission of the pathogen in the planting material. In one of three field experiments the contamination rate of planting stock influenced the disease incidence in field-grown garlic. The importance of planting stock as a source of inoculum was demonstrated here and should be evaluated relative to other potential sources such as crop debris, soil or alternate hosts in order to develop successful control strategies.  相似文献   

Nutritive value of edible forage from two <Emphasis Type="Italic">Leucaena leucocephala</Emphasis> cultivars with different growth habit and morphology     

E. González-García  O. Cáceres  H. Archimède  H. Santana 《Agroforestry Systems》2009,77(2):131-141

The nutritive value of edible forage from Leucaena leucocephala cv. Cunningham (CUNN) and cv. CNIA-250 (CNIA) was determined during the rainy (R) and dry (D) seasons of Cuba without fertilization or irrigation. Forage was supplied ad libitum and the French system of total faeces collection was used for nutritive value determination and expression by using six adult castrated Pelibuey wethers for each determination. There were noticeable differences in the chemical composition and nutritive value between the two cultivars which were also influenced by year season. The highest protein and energy content were found in CNIA and during the rainy season which could also explain its higher forage intake and digestibility, while CUNN expressed higher DM and nutrient yield throughout the year, mainly due to advantages in tree size and morphology (higher ramification and proportion of leaves, and acceptable branch length). Quality and nutritive value results indicated that these Leucaena cultivars have a suitable potential as supplements for sustainable ruminant nutrition strategies during both seasons of the year; CNIA, because of its smaller height, is strongly recommended for agrosilvopastoral small ruminant browsing systems.  相似文献   

A comparison of mortality rates between top height trees and average site trees   总被引：1，自引：0，他引：1  

Daniel Mailly  Mélanie Gaudreault  Geneviève Picher  Isabelle Auger  David Pothier 《Annals of Forest Science》2009,66(2):202-202

? Although comparisons between methods of selecting trees for site index estimates are well documented in the literature, little is known on mortality rates of different canopy tree cohorts used for that purpose.

? This study was initiated to test the hypothesis that the mortality rates of top height trees are lower than those of codominants only or a combination of codominant and dominant trees. To test this hypothesis, we used records from a network of permanent sample plots in Québec and studied the fate of different cohorts of site trees for five different species.

? Our results did not show clear evidence of lower mortality rates for top height trees. Instead we found that depending on the species, top height trees have lower (Populus tremuloides, Pinus banksiana), higher (Picea mariana, Abies balsamea) or equal mortality rates (Betula papyrifera) than codominant trees or codominant and dominant trees combined.

? These results suggest a tendency for shade intolerant species to maintain lower top height tree mortality rates over time when compared to shade tolerant species. In the latter case, it is also shown that spruce budworm epidemics (Choristoneura fumiferana) did not change the pattern of mortality rates of site trees of A. balsamea.

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Monitoring and efficacy of selected insecticides for European corn borer (<Emphasis Type="Italic">Ostrinia nubilalis</Emphasis> Hubn., Lepidoptera: Crambidae) control     

Renata Bažok  Jasminka Igrc Barèiæ  Tomislav Kos  Tanja Gotlin Èuljak  Martina Šiloviæ  Siniša Jelovèan  Antonela Kozina 《Journal of pest science》2009,82(4):311-319

The European corn borer (ECB), Ostrinia nubilalis (H?bner) (Lepidoptera: Crambidae), is the major arthropod pest of corn in Croatia. However, chemical control is carried out only in maize for seed production, and in sweet corn. A 3-year investigation was carried out in corn fields in northwest Croatia to establish the most attractive pheromone lure for ECB monitoring, the optimal timing of insecticide applications, and the efficacy of selected insecticides against ECB. During each of the 3 years, the pheromone lures E, Z and E/Z («Isagro») were evaluated in the field from May to July. Insecticides were sprayed 14–20 days after the maximal capture in 2002 and 2003. In 2004, three different trials were set up: one trial with one early treatment (when corn was in the R49 development stage according to the extended BBCH scale); one with one late treatment (when corn was in the R65 development stage according to the BBCH scale); and one with two treatments in both stages. In the trials studying Bacillus thuringiensis var. kurstaki (B.t.k.), insect growth regulators (IGR), spinosad and classical chemical insecticides were applied. Pheromone lure E was the most attractive for monitoring ECB flights throughout 2 years of investigation. Insecticide efficacy depended on application timing. The insecticides most suitable for integrated pest management (IPM) programs, including spinosad, B.t.k. and IGR, resulted in high (spinosad) to moderate (B.t.k.) efficacy. The efficacy of IGRs indicates the need for earlier application. The efficacy of chemical insecticides depended on the year and the insecticide. The organophosphate (OP) insecticides and pyrethroids gave moderate to good results; imidacloprid did not provide significant efficacy. One application of all insecticides based on proper (early) timing resulted in the same efficacy as two applications of the same insecticides.  相似文献   

Lack of fitness costs associated with pyriproxyfen resistance in the B biotype of Bemisia tabaci     

David W Crowder  Christa Ellers‐Kirk  Bruce E Tabashnik  Yves Carrière 《Pest management science》2009,65(3):235-240

BACKGROUND: The insect growth regulator pyriproxyfen has provided effective control of the whitefly Bemisia tabaci Gennadius in many countries. Here, whether or not fitness costs were associated with pyriproxyfen resistance in a laboratory‐selected resistant strain (QC02‐R) of the B biotype was determined. RESULTS: Mortality caused by pyriproxyfen and fitness traits over time were measured in unselected and selected hybrid strains, which were created by crossing individuals of the resistant strain with individuals of a susceptible strain. Fitness costs were not associated with resistance in QC02‐R, as mortality caused by pyriproxyfen did not increase over time in unselected hybrid strains and fitness traits were similar in unselected and selected hybrid strains. Using a new method to examine the inheritance of resistance, based on data from fitness cost experiments, it was estimated that pyriproxyfen resistance is controlled by two loci in the QC02‐R strain. CONCLUSION: The lack of fitness costs associated with pyriproxyfen resistance could promote the evolution of resistance in field populations with similar traits to QC02‐R. Copyright © 2008 Society of Chemical Industry  相似文献   

Seasonal variation in transcript abundance in cork tissue analyzed by real time RT-PCR     

Soler M  Serra O  Molinas M  García-Berthou E  Caritat A  Figueras M 《Tree physiology》2008,28(5):743-751

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Light interception and partitioning between shoots in apple cultivars influenced by training     

Stephan J  Sinoquet H  Donès N  Haddad N  Talhouk S  Lauri PE 《Tree physiology》2008,28(3):331-342

The effect of two training systems (Central Leader with branch pruning versus Centrifugal Training with minimal pruning, i.e., removal of fruiting laterals only) on canopy structure and light interception was analyzed in three architecturally contrasting apple (Malus domestica Borkh.) cultivars: 'Scarletspur Delicious' (Type II); 'Golden Delicious' (Type III); and 'Granny Smith' (Type IV). Trees were 3D-digitized at the shoot scale at the 2004 and 2005 harvests. Shoots were separated according to length (short versus long) and type (fruiting versus vegetative). Leaf area density (LAD) and its relative variance (xi), total leaf area (TLA) and crown volume (V) varied consistently with cultivar. 'Scarletspur Delicious' had higher LAD and xi and lower TLA and V compared with the other cultivars with more open canopies. At the whole-tree scale, training had no effect on structure and light interception parameters (silhouette to total area ratio, STAR; projected leaf area, PLA). At the shoot scale, Centrifugal Training increased STAR values compared with Central Leader. In both training systems, vegetative shoots had higher STAR values than fruiting shoots. However, vegetative and fruiting shoots had similar TLA and PLA in Centrifugal Trained trees, whereas vegetative shoots had higher TLA and PLA than fruiting shoots in Central Leader trees. This unbalanced distribution of leaf area and light interception between shoot types in Central Leader trees partly resulted from the high proportion of long vegetative shoots that developed from latent buds. These shoots developed in the interior shaded zone of the canopy and therefore had low STAR and PLA. In conclusion, training may greatly affect the development and spatial positioning of shoots, which in turn significantly affects light interception by fruiting shoots.  相似文献   

Mechanical analysis of the strains generated by water tension in plant stems. Part II: strains in wood and bark and apparent compliance     

Alméras T 《Tree physiology》2008,28(10):1513-1523

Tree stems shrink in diameter during the day and swell during the night in response to changes in water tension in the xylem. Stem shrinkage can easily be measured in a nondestructive way, to derive continuous information about tree water status. The relationship between the strain and the change in water tension can be evaluated by empirical calibrations, or can be related to the structure of the plant. A mechanical analysis was performed to make this relationship explicit. The stem is modeled as a cylinder made of multiple layers of tissues, including heartwood, sapwood, and inner and outer bark. The effect of changes in water tension on the apparent strain at the surface of a tissue is quantified as a function of parameters defining stem anatomy and the mechanical properties of the tissues. Various possible applications in the context of tree physiology are suggested.  相似文献   

Correction of moisture effects on near infrared calibration for the analysis of phenol content in eucalyptus wood extracts     

Thomas Giordanengo  Jean-Paul Charpentier  Jean-Michel Roger  Sylvie Roussel  Loïc Brancheriau  Gilles Chaix  Henri Baillères 《Annals of Forest Science》2008,65(8):803-803

? Methods based on near infrared spectroscopy used to assess wood properties are susceptible to variations in physical parameters (temperature, grain size, etc.). As wood is a hygroscopically sensitive material, we studied the effects of moisture on near infrared absorbance and calibration to accurately determine the application potential of this technique under routine.

? A collection of Eucalyptus urophylla × E. grandis hybrid wood pieces were analysed to obtain reference calibration of polyphenol contents in wood extracts via NIR spectra acquired under constant moisture conditions. Other specimens from the same source were assessed to obtain spectra for eight moisture contents spanning a broad variation range. The effects of moisture on absorption and on estimates based on a reference model were analysed.

? An increase in moisture content prompted a rise in near infrared absorption over the entire spectrum and for water O-H absorption bands. The polyphenol content estimates obtained by assessing specimens against the reference calibration at variable moisture contents revealed prediction bias. Five correction methods were then tested to enhance the robustness relative to moisture.

? In-depth calibration and external parameter orthogonalization (EPO) were found to be the most efficient methods for offsetting this factor.

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North American P type of Heterobasidion annosum shows pathogenicity towards Pinus halepensis in Italy     

M. Scirè  L. D’Amico  E. Motta  T. Annesi 《Forest Pathology》2008,38(5):299-301

During a survey on the distribution of Heterobasidion root rot, the North American P group of H. annosum was recorded causing root rot on Aleppo pine, Pinus halepensis, in the gardens of a historical villa in Rome. This is the first report of Heterobasidion root rot on P. halepensis in its natural distribution area, the Mediterranean Basin.  相似文献