Penetration of light into carpet, and responses of the European house-dust mite (Dermatophagoides pteronyssinus) to varying light intensity and diurnal cycle

This study examined the question of what effect exposure to light might play in determining the vertical distribution of house-dust mites in carpet, and the degree to which light penetrates worn and unworn carpets of different pile conformation (loop- versus cut-pile), height and colour. The effect on population increase of a diurnal lighting cycle versus continual darkness was also investigated. It was found that the penetration of light into carpets was largely unaffected by pile colour or conformation. Pile height was an important factor, however, and for a given height within the pile, light intensity was higher in carpets subjected to a greater degree of wear. This corresponded to the reduction in effective pile height that occurs with carpet use. Whilst the differences observed were sometimes large (up to two-fold for a given height within the pile), Petri dish studies suggested no mite preference for habitation of areas of low light intensity compared to high intensity. Additionally, culturing mites under a diurnal light cycle was shown to be no more efficient than culturing in complete darkness. These results suggest that exposure to light is not an important determinant of house-dust mite behaviour, or their ability to colonise textile substrates.     

Generation of a transgenic rice seed-based edible vaccine against house dust mite allergy

As an alternative approach to conventional allergen-specific immunotherapy, transgenic rice seed expressing a major house dust mite (HDM) allergen, Der p 1, was developed as an edible vaccine. The C-terminal KDEL-tagged Der p 1 allergen specifically accumulated in seed endosperm tissue under the control of the endosperm-specific GluB1 promoter. Der p 1 reached a maximum concentration of 58 μg/grain and was deposited in the endoplasmic reticulum (ER)-derived protein body I (PB-I). Plant-derived Der p 1 was posttranslationally modified with high-mannose-type glycan structures. Glycosylated Der p 1 displayed reduced IgE binding capacity in comparison with its unglycosylated counterpart in vitro. Our results indicate that transgenic Der p 1 rice seeds are a safe, potential oral delivery vaccine for the treatment of HDM allergy.     

Parasitoid-induced mortality of house fly pupae by Pteromalid wasps in the laboratory

House fly, Musca domestica L., pupae were exposed to six species of pteromalid parasitoids, Muscidifurax zaraptor Kogan and Legner, M. raptor Girault and Sanders, M. raptorellus Kogan and Legner, Pachycrepoideus vindemiae (Rondani), Spalangia nigroaenea Curtis, and Urolepis rufipes Ashmead. Exposures were made for 48 h at six parasitoid-to-host ratios to measure the effect of parasitoid density on parasitoid-induced mortality (PIM) of hosts (excluding mortality as measured by parasitoid emergence). PIM was evident at all parasitoid-to-host ratios for all six species. Fly eclosion declined with a corresponding increase in the parasitoid-to-host ratio; the reverse was generally true for PIM. Parasitoid emergence increased initially with a corresponding increase in the parasitoid-to-host ratio to a point (depending on the parasitoid species), but then declined. The three Muscidifurax spp. and P. vindemiae exhibited similar behavior and generally avoided previously stung hosts until ovipositional restraints broke down at the higher parasitoid-to-host ratios. S. nigroaenea and U. rufipes exhibited little ovipositional restraint, resulting in a high proportion of PIM of hosts. Understanding factors that influence PIM will provide better evaluations of field releases of parasitoids to control flies and will aid in the development of the most economic procedures for large scale rearing of pteromalid parasitoids.     

番茄潜叶蛾对不同类型杀虫剂的敏感性

【目的】番茄潜叶蛾是一种对番茄具有毁灭性危害的世界入侵害虫,本研究测定了不同类型药剂对入侵害虫番茄潜叶蛾的毒力活性及防治效果,为生产中科学防治番茄潜叶蛾提供理论依据。【方法】采用室内毒力测定方法,计算各药剂对不同龄期幼虫的毒力回归方程;采用田间防效评价方法,得出药后1~21 d各药剂对幼虫的防效,综合比较分析不同类型药剂对番茄潜叶蛾的控制作用。【结果】室内毒力测定结果表明,植物源杀虫剂印楝素和抗生素类杀虫剂甲氨基阿维菌素苯甲酸盐对番茄潜叶蛾的毒性相对最强,其中印楝素对1龄幼虫的毒力最强,其LC₅₀为3.22 mg·L^-1,甲氨基阿维菌素苯甲酸盐对2~4龄幼虫的毒力最强,其LC₅₀分别为7.1046、7.5663和4.375 mg·L^-1;其次是苯甲酰脲类杀虫剂氯虫苯甲酰胺和合成杀虫剂乙基多杀菌素;拟除虫菊酯类杀虫剂高效氯氰菊酯、昆虫生长调节剂类杀虫剂甲氧虫酰肼对番茄潜叶蛾也有较好的毒杀作用;新烟碱类杀虫剂吡虫啉、噻虫嗪、烯啶虫胺对番茄潜叶蛾的毒性相对较弱。田间防效结果表明,抗生素类杀虫剂甲氨基阿维菌素苯甲酸盐的防效相对最高、持效性最好,药后第7、14和21天防效分别为74.11%、71.42%和60.03%;其次是苯甲酰脲类杀虫剂氯虫苯甲酰胺、合成杀虫剂乙基多杀菌素和拟除虫菊酯类杀虫剂高效氯氰菊酯;植物源杀虫剂印楝素的持效性较好,药后第7~21天的防效均高于50%;昆虫生长调节剂类杀虫剂甲氧虫酰肼以及新烟碱类杀虫剂吡虫啉、噻虫嗪、烯啶虫胺对番茄潜叶蛾的田间防效相对较弱。【结论】抗生素类杀虫剂甲氨基阿维菌素苯甲酸盐、苯甲酰脲类杀虫剂氯虫苯甲酰胺和合成杀虫剂乙基多杀菌素可作为生产中防治番茄潜叶蛾的首选药剂,具有较好的应用前景,植物源杀虫剂印楝素和拟除虫菊酯类杀虫剂高效氯氰菊酯可作为交替使用药剂。     

House dust mite, Dermatophagoides pteronissinus increases expression of MCP-1, IL-6, and IL-8 in human monocytic THP-1 cells

The house dust mite (Dermatophagoides pteronissinus) plays an important role in the pathogenesis of allergic diseases, including atopic dermatitis, and asthma. Monocyte chemotactic protein 1 (MCP-1/CCL2)/IL-6/IL-8 (CXCL8) plays a pivotal role in mediating the infiltration of various cells into the skin of atopic dermatitis and psoriasis. The aim of this study was to investigate the effect of D. pteronissinus extract (DpE) on expression of MCP-1/IL-6/IL-8 mRNA and protein and the signal transduction in the human monocytic cell line, THP-1. The mRNA and protein expression of MCP-1/CCL2, IL-6, and IL-8 were elevated by DpE in a time and dose-dependent manner in THP-1 cells. The increased expression of MCP-1, IL-6, and IL-8 was not affected by aprotinin (serine protease inhibitor) or E64 (cysteine protease inhibitor). We found that MCP-1 and IL-6 expression due to DpE was related to Src, protein kinase C δ (PKC δ), extracellular-signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK) and IL-8 expression was involved in Src family tyrosine kinase, PKC δ, ERK. DpE increased the phosphorylation of ERK and p38 MAPK after 5 min and peaked at 30 min. The activation was significantly blocked by PP2, an inhibitor of Src family tyrosine kinase and rottlerin, an inhibitor of PKC δ (p < 0.01). DpE increases MCP-1, IL-6, and IL-8 expression and transduces its signal via Src family tyrosine kinase, PKC, and ERK in a protease-independent manner. This finding may contribute to the elucidation of the pathogenic mechanism triggered by DpE .     

Structure of the house dust mite allergen Der f 2: implications for function and molecular basis of IgE cross-reactivity

The X-ray structure of the group 2 major allergen from Dermatophagoides farinae (Der f 2) was determined to 1.83 A resolution. The overall Der f 2 structure comprises a single domain of immunoglobulin fold with two anti-parallel beta-sheets. A large hydrophobic cavity is formed in the interior of Der f 2. Structural comparisons to distantly related proteins suggest a role in lipid binding. Immunoglobulin E (IgE) cross-reactivity between group 2 house dust mite major allergens can be explained by conserved surface areas representing IgE binding epitopes.     

不同土壤水盐条件下多枝柽柳(Tamarix ramosissima)对胡杨(Populus euphratica)幼苗的影响

目前胡杨更新困难,种群处于退化阶段,而与其生态位高度重叠的多枝柽柳却在扩张。为探讨多枝柽柳对胡杨生长的影响,本研究设置了3个水平的水分、盐分梯度,对胡杨进行了单种和混种的盆栽控制实验,通过测定胡杨幼苗的生长和存活状况,分析不同水、盐梯度下多枝柽柳如何影响胡杨生长。结果表明：（1）多枝柽柳伴生降低当年生胡杨幼苗的存活率,随着水分条件改善,胡杨存活率提高,而盐分对存活率没有显著的影响。（2）水分、盐分和伴生模式几个因子对胡杨的生长特征的影响存在显著的交互作用（P<0.05）。各水盐条件下,多枝柽柳会不同程度降低胡杨幼苗的株高、主根长和地上地下生物量,而根冠比增大。混种条件下,胡杨幼苗对水盐的响应更为敏感。（3）相对竞争强度对水盐环境有明显的响应（P<0.05）,随水分条件改善,地上、地下相对竞争强度降低。多枝柽柳对胡杨的生长产生不良影响的机制是通过快速消耗土壤的水分,从而导致胡杨幼苗水分亏缺。土壤水分条件是胡杨和多枝柽柳幼苗共存的关键因素,在水分供给不足的情况下,对水分偏好的差异导致胡杨无法通过实生苗进行有效的更新从而加剧胡杨种群的衰退,而多枝柽柳更为耐旱的特性使其逐步占据河岸的生境。我们的研究结果强调了两个树种对环境因子的适应性差异决定了河岸带植被发育过程中植物-土壤的相互作用导致胡杨在演替过程中表现出的衰退现象。     

Practical aspects of fumonisin production under laboratory conditions

Studies were performed to develop an efficient method for fumonisin toxin production in sufficient quantities for animal toxicological experiments, on the basis of three earlier published fumonisin toxin production methods. Three absolutely necessary factors were taken into account and tested in a serial experiment. TheFusarium verticillioides strain MRC 826 was directly inoculated onto soaked, autoclaved, whole maize kernels (50 g/1.71 jar). The inoculation was performed by standard spore suspension (l×l0⁶/ml), a 5/2 surface/volume culture was prepared and incubated at 25 °C for 5 weeks. To maintain the optimal a_w of approximately 1.00, the evaporated water was re-filled weekly. A final concentration of 4454±1060.9 ppm fumonisin B₁ was reached, with good repeatability. In the laboratory practice, consistent production of constant amounts of FB₁ can be obtained by applying the above settings.     

Properties of Bacillus anthracis spores prepared under various environmental conditions

Bacillus anthracis makes highly stable, heat-resistant spores which remain viable for decades. Effect of various stress conditions on sporulation in B. anthracis was studied in nutrient-deprived and sporulation medium adjusted to various pH and temperatures. The results revealed that sporulation efficiency was dependent on conditions prevailing during sporulation. Sporulation occurred earlier in culture sporulating at alkaline pH or in PBS than control. Spores formed in PBS were highly sensitive towards spore denaturants whereas, those formed at 45°C were highly resistant. The decimal reduction time (D-10 time) of the spores formed at 45°C by wet heat, 2 M HCl, 2 M NaOH and 2 M H₂O₂ was higher than the respective D-10 time for the spores formed in PBS. The dipicolinic acid (DPA) content and germination efficiency was highest in spores formed at 45°C. Since DPA is related to spore sensitivity towards heat and chemicals, the increased DPA content of spores prepared at 45°C may be responsible for increased resistance to wet heat and other denaturants. The size of spores formed at 45°C was smallest amongst all. The study reveals that temperature, pH and nutrient availability during sporulation affect properties of B. anthracis spores.     

Establishment of phosphate-solubilizing strains of Azotobacter chroococcum in the rhizosphere and their effect on wheat cultivars under green house conditions

A pot experiment was conducted in the green house to investigate the establishment of phosphate solubilizing strains of Azotobacter chroococcum, including soil isolates and their mutants, in the rhizosphere and their effect on growth parameters and root biomass of three genetically divergent wheat cultivars (Triticum aestivum L.). Five fertilizer treatments were performed: Control, 90 kg N ha^—1, 90 kg N + 60 kg P₂O₅ ha^—1, 120 kg N ha^—1 and 120 kg N + 60 kg P₂O₅ ha^—1. Phosphate solubilizing and phytohormone producing parent soil isolates and mutant strains of A. chroococcum were isolated and selected by an enrichment method. In vitro phosphate solubilization and growth hormone production by mutant strains was increased compared with soil isolates. Seed inoculation of wheat varieties with P solubilizing and phytohormone producing A. chroococcum showed better response compared with controls. Mutant strains of A. chroococcum showed higher increase in grain (12.6%) and straw (11.4%) yield over control and their survival (12—14%) in the rhizosphere as compared to their parent soil isolate (P4). Mutant strain M37 performed better in all three varieties in terms of increase in grain yield (14.0%) and root biomass (11.4%) over control.     

Influence of mite infestation on the longevity and fecundity of the mosquitoMansonia uniformis (Diptera: Insecta) under laboratory conditions

A study relating to the influence of mite infestation on the longevity and fecundity of the mosquito,Mansonia uniformis was carried out in the laboratory. It was found that the mite parasitism does influence the quantity of blood ingested, survivorship and the time lag between feeding and egg-laying. However fecundity and hatching percentages were not affected.     

Treatment with a sphingosine analog after the inception of house dust mite-induced airway inflammation alleviates key features of experimental asthma

Background

In vivo phosphorylation of sphingosine analogs with their ensuing binding and activation of their cell-surface sphingosine-1-phosphate receptors is regarded as the main immunomodulatory mechanism of this new class of drugs. Prophylactic treatment with sphingosine analogs interferes with experimental asthma by impeding the migration of dendritic cells to draining lymph nodes. However, whether these drugs can also alleviate allergic airway inflammation after its onset remains to be determined. Herein, we investigated to which extent and by which mechanisms the sphingosine analog AAL-R interferes with key features of asthma in a murine model during ongoing allergic inflammation induced by Dermatophagoides pteronyssinus.

Methods

BALB/c mice were exposed to either D. pteronyssinus or saline, intranasally, once-daily for 10 consecutive days. Mice were treated intratracheally with either AAL-R, its pre-phosphorylated form AFD-R, or the vehicle before every allergen challenge over the last four days, i.e. after the onset of allergic airway inflammation. On day 11, airway responsiveness to methacholine was measured; inflammatory cells and cytokines were quantified in the airways; and the numbers and/or viability of T cells, B cells and dendritic cells were assessed in the lungs and draining lymph nodes.

Results

AAL-R decreased airway hyperresponsiveness induced by D. pteronyssinus by nearly 70%. This was associated with a strong reduction of IL-5 and IL-13 levels in the airways and with a decreased eosinophilic response. Notably, the lung CD4⁺ T cells were almost entirely eliminated by AAL-R, which concurred with enhanced apoptosis/necrosis in that cell population. This inhibition occurred in the absence of dendritic cell number modulation in draining lymph nodes. On the other hand, the pre-phosphorylated form AFD-R, which preferentially acts on cell-surface sphingosine-1-phosphate receptors, was relatively impotent at enhancing cell death, which led to a less efficient control of T cell and eosinophil responses in the lungs.

Conclusion

Airway delivery of the non-phosphorylated sphingosine analog, but not its pre-phosphorylated counterpart, is highly efficient at controlling the local T cell response after the onset of allergic airway inflammation. The mechanism appears to involve local induction of lymphocyte apoptosis/necrosis, while mildly affecting dendritic cell and T cell accumulation in draining lymph nodes.     

Efficacy of entomopathogenic nematodes against neonate larvae of <Emphasis Type="Italic">Capnodis tenebrionis</Emphasis> (L.) (Coleoptera: Buprestidae) in laboratory trials

The efficacy of five entomopathogenic nematode strains of the families Steinernematidae and Heterorhabditidae was tested against the neonate larvae of Capnodis tenebrionis. The nematode strains screened included two of Steinernema carpocapsae (Exhibit and M137), and one each of S. feltiae (S6), S. arenarium (S2), and Heterorhanditis bacteriophora (P4). Exposure of neonate larvae of Capnodis to 10 and 150 infective juveniles (IJs) per larva (equivalent to 3 and 48 IJs/cm² respectively) in test tubes with sterile sand, resulted in mortality between 60–91% and 96–100%, respectively. At a concentration of 150 IJs/larva, all of the nematode strains were highly virulent. Both S. carpocapsae strains (Exhibit and M137) caused infection and mortality to larvae more quickly than the other strains. However, at a lower concentration assay (10 IJs/larva), S. arenarium was the most virulent strain. The penetration rate as an indicator of entomopathogenic nematode infection was also evaluated. The highest value was recorded for S. arenarium (36%), followed by H. bacteriophora (30.6%), S. feltiae (23.1%), and S. carpocapsae (20.7%).     

Survival of Theileria parva-infected adult Rhipicephalus appendiculatus under laboratory and quasi-natural conditions

Adult Rhipicephalus appendiculatus Muguga, having high or low intensities of Theileria parva Muguga infection in their salivary glands, were exposed to 20 °C and 85% relative humidity in the laboratory or quasi-natural conditions. Survival of the ticks and T. parva infections in their salivary glands was then monitored over a two year period. Ticks, having an average infection level of 2 infected acini per female, survived for up to 70 or 106 weeks after moulting under the laboratory or quasi-natural conditions respectively. Those having an infection level of 26 infected acini per female, survived for a similar duration except that those under quasi-natural conditions survived for a slightly shorter duration (102 weeks). Similarly, T. parva parasites survived for much longer periods under quasi-natural conditions than under the laboratory conditions. They survived for up to 38 or 78 weeks post salivary gland infection under the laboratory or quasi-natural conditions respectively in both categories of infection levels. There was apparently a density dependent relationship in T. parva survival, with a dramatic fall in infection occurring in ticks with high levels of infection between weeks 10 and 18 or weeks 38 and 46 post salivary gland infection in those exposed to laboratory or quasi-natural conditions before levelling off. This revised version was published online in July 2006 with corrections to the Cover Date.     

Development of the starfish <Emphasis Type="Italic">Asterias amurensis</Emphasis> under laboratory conditions

Under laboratory conditions the development of the starfish Asterias amurensis Lütken from Vostok Bay (Sea of Japan) was studied at 14 and 17°C. At 14°C and a salinity of 31.6–32.6, ciliated coeloblastulae hatched from egg envelopes 19 h after fertilization. At this temperature the development proceeded slowly and stopped at the stage of bipinnaria. At 17°C and normal salinity of seawater, the development of A. amurensis was successful. The swimming blastula appeared in 14 h. It took 30.5 h for the embryos to reach the gastrula stage. The larvae began swimming in a horizontal position with the apical tip ahead. The dipleurula appeared at 60 h. These larvae began feeding. At 71 h after the beginning of development, the early bipinnaria has developed. In the larva, the edged ciliated band, the preoral plate, and the anal plate were already formed. At the age of 4.2 days, the larvae reached the stage of bipinnaria and the brachiolaria stage developed by 26–28 days after fertilization. The larvae had three identical brachiolar arms with attachment papillae on their tips and an attachment disk. In 37–44 days (at 17°C) the pelagic phase of A. amurensis development was completed by the attachment of larvae to the bottom plates and termination of metamorphosis. Most likely, the specificity to a substrate is not expressed in the brachiolaria of A. amurensis. They can settle on almost any hard substrate which is coated with a bacterial film. The newly settled juvenile starfish had five well-developed arms and moved using their ambulacral podia.Original Russian Text Copyright © 2005 by Biologiya Morya, Kashenko.     

Comparison of growth habits under various light conditions between two climax species, Castanopsis sieboldii and Castanopsis cuspidata, with special reference to their shade tolerance

Two experiments were conducted to examine the difference in shade tolerance between two climax species, Castanopsis sieboldii and Castanopsis cuspidata, in Aichi Prefecture in the warm-temperate climate of Japan. In the growth experiment, the seedlings of the two species were raised under five light conditions, 100%, 30%, 10%, 3% and 1% relative light intensity (RLI). The growth of C. sieboldii highly exceeded that of C. cuspidata, particularly under higher light conditions. In the heavy shading experiment, the seedlings of the two species were grown under three light conditions (0, 0.15 and 0.3% RLI). While all seedlings of C. sieboldii died within 2 years under 0.15 and 0.3% RLI, about half of the seedlings of C. cuspidata survived more than 2 years under 0.15% RLI, and about 70% survived more than 4 years under 0.3% RLI. It was concluded that C. cuspidata was more shade tolerant than C. sieboldii, and the possibility that C. sieboldii might be more tolerant of the drought stress than C. cuspidata was discussed.     

Performance of the tsetse fly Glossina pallidipes reared under simple laboratory conditions

A simple grass-thatched hut was used to rear Glossina pallidipes Austen. Constructed to allow free flow of air, the temperature and humidity inside correspond to that of the outside environment. Pupae used to start the colony were obtained from pregnant females from Lambwe Valley, Western Kenya. Nine day-old females were paired with 12 day-old males for 7 days after which they were separated.Colony performance was evaluated on the basis of female survival, number and weight of puparia produced, and mortality rates. The emergence rate of puparia weighing more than 30 mg was above 80%. Data on the performance of the colony between June 1985 and June 1986 are presented. We suggest that the simple nature of the rearing facility and its direct contact with the outside environment have facilitated the colonization of the flies.

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Résumé Une cage très simple, conçue pour assurer l'arrivé d'air, et le maintien de l'humidité et de loa température extérieure, a été employée pour conserver et élever G. pallidipes. Les pupes utilisées pour constituer la souche provenaient de Lambwe valley (ouest du Kénya). Des couples de femelles vieilles de 9 jours et de mâles de 12 jours ont été consitués, les sexes ont ensiute été séparés. La performance de la souche a été estimée en fonction de la survie des femelles et du nombre et du poids des pupes produites, et des taux de mortalité. Plus de 80% des pupes ont pesé 30 mg et plus, et le taux d'émergence a été de 80%. Les résultats fournis concernent les performances observées entre juin 1985 et juin 1986. Nous estimons que la simplicité du dispositif d'élevage et le contact direct avec les conditions écologiques externes ont facilité l'éstablissement de la souche.

     

Combination of the antifeedant bean flour and the predator Cheyletus malaccensis suppresses storage mites under laboratory conditions

Stored product mites are pests of serious economic and medical importance. Recently, it has been shown that the biological control of these pests based on the use of natural compounds and predators had a high potential for success. In this study, we investigated the suppression of three pest mites by combination of the predator Cheyletus malaccensis Oudemans, 1913 and bean flour (Phaseolus vulgaris), which is an antifeedant. Wheat grain (100 g) was contaminated with 100 individuals (Acarus siro (Linnaeus, 1758), Aleuroglyphus ovatus (Troupeau, 1878) or Tyrophagus putrescentiae (Schrank, 1781)). We added bean flour in concentrations of 0, 1, 5 and 10 g kg⁻¹ (wt/wt) and/or the predator with initial predator/prey ratios 0, 1/50, 1/25 and 1/10. The experiment was carried out under abiotic conditions that are optimal for pest development. After 21 days, pest and predators numbers were recorded. Application of flour significantly reduced populations of A. siro, slightly reduced populations of T. putrescentiae, the efficiency increased with increasing concentration. A. ovatus was not affect by bean flour. Populations of all mite species were successfully reduced by the sole addition of C. malaccensis, with a higher efficiency at higher Cheyletus ratios. The additive effect of the predator and flour was mainly apparent in the reduction of T. putrescientae. The population of C. malaccensis was not affected by the presence of bean flour. It is therefore recommended to use bean flour for the reduction of A. siro, a combination of bean flour and Cheyletus for the reduction of T. putrescientae, and only Cheyletus for the reduction of A. ovatus. Handling Editor: Arne Janssen.     

Biological control of bacterial spot of tomato under field conditions at several locations in North America

Following the relatively successful biological control of bacterial speck of tomato under field conditions at several locations (Phytopathology 92 (2002) 1284), similar selection and testing strategies were employed in an effort to isolate an effective biological control agent for bacterial spot of tomato. Fifty potential biological control agents were isolated from tomato foliage in Alabama (AL) and Florida (FL) and tested under greenhouse conditions in AL for the ability to reduce the foliar severity of bacterial spot of tomato (Lycopersicon esculentum), which is caused by either Xanthomonas campestris pv. vesicatoria or Xanthomonas vesicatoria. Three pseudomonads that provided protection against bacterial speck also were included in the tests. The strains which were most efficacious (i.e., high mean percentage reduction) and consistent (i.e., low standard deviation) in reducing bacterial spot severity in repeated greenhouse experiments were selected for field experiments conducted over the period 1996–1998. Among these strains were Cellulomonas turbata BT1, which provided the highest mean reduction in disease severity [45.2% (SD = 21.0)], and Pseudomonas syringae Cit7 [36.4% (SD = 12.2)], which was the most consistent. Field experiments were conducted in Shorter, AL; Bradenton and Sanford, FL; Clinton, North Carolina; Wooster, Ohio; and London, Ontario, Canada. The highest mean reductions in severity of bacterial spot on foliage, averaged across all locations, were provided by P. syringae Cit7 [28.9% (SD = 11.6)] and Pseudomonas putida B56 [23.1% (SD = 7.4)]. The efficacy and consistency of P. syringae Cit7 against bacterial spot were very similar to those achieved against bacterial speck [28.3% (SD = 12.7)] (Phytopathology 92 (2002) 1284). Unfortunately, neither the bacterial strains nor the standard copper bactericides consistently reduced disease incidence on fruit.     

Three native Pseudomonas fluorescens strains tested under growth chamber and field conditions as biocontrol agents against damping-off in alfalfa

Alfalfa (Medicago sativa) is one of the most important crops used in Uruguay for livestock feeding. Seedling diseases, particularly damping-off, are a critical factor which limits its establishment. Three native Pseudomonas fluorescens strains, UP61.2, UP143.8 and UP148.2, previously isolated from Lotus corniculatus, were evaluated to determine their efficacy as biological control agents for alfalfa seedling diseases in the field. Their compatibility with the alfalfa-Sinorhizobium meliloti symbiosis was also assessed. In growth chamber conditions seed inoculation with Pseudomonas strains did not affect different parameters of alfalfa-rhizobium symbiosis as shown by nodulation rate and shoot dry weight of plants. The presence of the commercial inoculant strains of S. meliloti did not impair colonization by the P. fluorescens and vice versa. In field trials the dynamics of rhizobial rhizospheric populations were not affected by the presence of P. fluorescens. Each P. fluorescens strain successfully colonized alfalfa roots at adequate densities for biocontrol activity. Results showed that P. fluorescens strains provided a 10–13% increase in the number of established plants relative to the control, an intermediate result compared to the fungicide treatment (24%). The alfalfa above-ground biomass was increased by 13% and 15–18% in the presence of the fungicide and P. fluorescens strains, respectively. Therefore, results from this study demonstrated that the three P. fluorescens strains provided effective control against soil-borne pathogens and suggest a potential use in the development of a commercial inoculant to be applied for the control of legume seedling diseases.