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51.
ABSTRACT Two strains of plant growth-promoting rhizobacteria (PGPR), Bacillus pumilus SE34 and Pseudomonas fluorescens 89B61, elicited systemic protection against late blight on tomato and reduced disease severity by a level equivalent to systemic acquired resistance induced by Phytophthora infestans or induced local resistance by chemical inducer beta-amino butyric acid (BABA) in greenhouse assays. Germination of sporangia and zoospores of P. infestans on leaf surfaces of tomato plants treated with the two PGPR strains, pathogen, and chemical BABA was significantly reduced compared with the noninduced control. Induced protection elicited by PGPR, pathogen, and BABA were examined to determine the signal transduction pathways in three tomato lines: salicylic acid (SA)-hydroxylase transgenic tomato (nahG), ethylene insensitive mutants (Nr/Nr), and jasmonic acid insensitive mutants (def1). Results suggest that induced protection elicited by both bacilli and pseudomonad PGPR strains was SA-independent but ethylene- and jasmonic acid-dependent, whereas systemic acquired resistance elicited by the pathogen and induced local resistance by BABA were SA-dependent. The lack of colonization of tomato leaves by strain 89B61 suggests that the observed induced systemic resistance (ISR) was due to systemic protection by strain 89B61 and not attributable to a direct interaction between pathogen and biological control agent. Although strain SE34 was detected on tomato leaves, ISR mainly accounted for the systemic protection with this strain. 相似文献
52.
Physiological responses of transported goats treated with ascorbic acid during the hot-dry season 总被引:1,自引:0,他引:1
The aim of the present study was to determine the physiological responses of transported Red Sokoto goats (RSG) treated with ascorbic acid (AA). Ten RSG treated orally with ascorbic acid served as experimental subjects, while seven goats treated with sterile water served as the control. The goats were transported for 8 h. The ambient temperature and relative humidity during the study period fluctuated between 21 and 38°C and 51 and 91%, respectively, which indicated that the season was thermally stressful and did not favor transportation of goats. The rectal temperature obtained in the control goats was significantly higher (P < 0.01) than the value in the experimental goats after transportation. There was a significant decrease (P < 0.05) in eosinophil counts and an increase (P < 0.01) in neutrophil counts and neutrophil : lymphocyte ratio recorded in the control goats after transportation, which suggested that the control goats were physically and emotionally stressed. The control goats lost 11.9% of their initial liveweight, while the experimental goats lost only 1.04% after transportation. Multiple stresses, including extreme meteorological factors, acted upon the transported goats and impaired their homeostatic mechanism. In conclusion, AA administration in goats reduced the adverse effects of road transportation stress. 相似文献
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甜瓜蔓枯病菌子实体法分离及A型菌株产孢条件研究 总被引:1,自引:0,他引:1
为解决甜瓜蔓枯病菌(Didymellabryoniae)组织分离法中枯萎病菌污染和单孢分离法操作复杂的问题,采用挑取单个子实体分离纯化获得甜瓜蔓枯病菌A型菌株。该菌株在12h荧光/12h黑暗的常规光照条件下,不能形成分生孢子器,但经过一定时间的暗处理和间歇紫外灯(12h紫外灯/12h黑暗)照射后则能够产生大量分生孢子。研究了光照、温度、pH值、培养基、碳源、氮源对产孢量的影响。综合各种因素,A型菌株产生分生孢子的最佳条件为:7d暗培养和4d间歇紫外灯处理的光照条件下,只含有磷酸二氢氨的马铃薯平板培养基,25℃时产生的分生孢子量最多。 相似文献
55.
Chu-Hui Chiang Chun-Yee Lee Ching-Hsien Wang Fuh-Jyh Jan Shih-Shun Lin Tsung-Chi Chen Joseph A. J. Raja Shyi-Dong Yeh 《European journal of plant pathology / European Foundation for Plant Pathology》2007,118(4):333-348
Papaya ringspot virus (PRSV) HA 5-1, a nitrous acid-induced mild mutant of severe strain HA, widely applied for control of PRSV by cross-protection,
was used to study the genetic basis of attenuation. Using infectious clones, a series of recombinants was generated between
HA 5-1 and HA and their infectivity was analyzed on the systemic host papaya and the local lesion host Chenopodium quinoa. The recombinants that contained mutations in P1 and HC-Pro genes caused attenuated infection on papaya without conspicuous
symptoms, similar to HA 5-1. The recombination and sequence analyses strongly implicated two amino acid changes in the C-terminal
region of P1 and two in HC-Pro of HA 5-1 involved in the attenuated infection on papaya. The recombinants that infected C. quinoa plants without local lesions contained the same mutations in the C-terminal region of HC-Pro for attenuated infection on
papaya. We conclude that both P1 and HC-Pro bear important pathogenicity determinants for the infection on the systemic host
papaya and that the mutations in HC-Pro affecting pathogenicity on papaya are also responsible for the inability to induce
hypersensitive reaction on C. quinoa. 相似文献
56.
Joseph Aubert Mouen Bedimo Daniel Bieysse Ibrahim Njiayouom Jean Pierre Deumeni Christian Cilas Jean Loup Nottéghem 《European journal of plant pathology / European Foundation for Plant Pathology》2007,119(4):391-400
In the high altitude regions of Africa, coffee berry disease (CBD), caused by Colletotrichum kahawae, is the main constraint for arabica coffee (Coffea arabica) production. However, certain agricultural practices can reduce losses caused by the disease and thereby promote optimum
production. On small family farms in Cameroon, mixed cropping with fruit trees, intercropping with food crops and maintenance
pruning of coffee trees are very widespread agricultural practices that can affect CBD epidemics. Consequently, an epidemiological
study was conducted to assess how cultural practices affected the disease in an arabica coffee smallholding in Cameroon. The
disease was monitored on a weekly basis over four successive years (2002–2005) on coffee trees in diverse cultural situations.
Cultural practices likely to reduce losses due to CBD were identified. The infection rate was significantly lower on coffee
trees grown intensively than on coffee trees grown in the traditional manner. Coffee trees located under the shade of fruit
trees were significantly less attacked than those located in full sunlight. In addition, berries on the leafless parts of
branches, near the main trunk of the coffee tree, were less infected than those on leafy sections. These results show that
maintenance pruning, removal of mummified berries, and mixed cropping with shade plants are cultural practices which create
environmental conditions that limit CBD development. 相似文献
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Roots from healthy and diseased mature ponderosa pine, Pinus ponderosa Laws., trees were excavated from a site near Burns, Oregon. The diseased trees were infected with black-stain root disease, Leptographium wageneri Kendrick, or annosus root disease, Heterobasidion annosum (Fr.) Bref., or both. Axial hydraulic conductivity of the roots was measured under a positive head pressure of 5 kPa, and the conducting area was stained with safranin dye to determine specific conductivity (k(s)). In diseased roots, only 8-12% of the cross-sectional xylem area conducted water. Resin-soaked xylem completely restricted water transport and accounted for 13-16% of the loss in conducting area. In roots with black-stain root disease, 17% of the loss in conducting area was associated with unstained xylem, possibly resulting from occlusions or embolisms. Based on the entire cross-sectional area of infected roots, the k(s) of roots infected with black-stain root disease was 4.6% of that for healthy roots, whereas the k(s) of roots infected with annosus root disease was 2.6% of that for healthy roots. Although these low values were partly the result of the presence of a large number of diseased roots (72%) with no conducting xylem, the k(s) of functional xylem of diseased roots was only 33% of that for healthy roots. The low k(s) values of functional xylem in diseased roots may be caused by fungus induced occlusions preceding cavitation and embolism of tracheids. The k(s) of disease-free roots from diseased trees was only 70% of that for healthy roots from healthy trees. The disease-free roots had the same mean tracheid diameter and tissue density as the healthy roots, suggesting that the lower k(s) in disease-free roots of diseased trees may also have been caused by partial xylary occlusions. 相似文献
60.
Paul Joseph Dimitri Bakirtzis Audrey Vieille 《Wood material science & engineering》2015,10(1):130-144
AbstractSaving lives and properties are of primary importance in fire disasters. Unfortunately, current fire detectors are not fast enough to allow the detection of many fires, especially, at the smouldering stages. Some preliminary studies on laevoglucosan (LG), as an important product from cellulose degradation, have shown interesting properties and could be detected by devices classified as “electronic noses” (e-noses). In the present work, the mechanisms of pyrolysis of some ligno-cellulosic materials were investigated using thermo-gravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy and by a tube furnace with a view to determining the major degradation products from wood, white paper and cardboard samples. Additionally, an odour sensor, made of tin oxide semiconductor thin film, was employed to evaluate its sensitivity in detecting LG. It was found that LG can be readily found among the thermal degradation products of cellulosic materials in question, and that the metal oxide sensor employed was sufficiently sensitive in detecting its presence. Therefore, the work opens up the potential of using such a sensor as an “e-nose” for the early detection of fires stemming from forest product fire loads in storage places and in other enclosures. 相似文献