荧光93菌体和代谢物对全蚀病菌和小麦生长影响的初步研究

对荧光假单胞菌工程菌剂“荧光93”菌体和代谢物的作用特性进行了比较。结果表明:该菌剂能保护小麦根系免遭全蚀病危害,对植株生长有促进作用。菌体的抑菌能力强于代谢物,浸种处理防效分别为44.8％和27.8％;代谢物具有更强的刺激植株生长作用,在无病条件下,代谢物灌根处理鲜重增加34.5％,菌体处理鲜重增加7.5％。培养基成份对代谢物的作用有一定影响:以马铃薯葡萄糖培养产生的代谢物,抑菌效果好;营养肉汁酵母粉培养产生的代谢物,促生作用好。据此推断,荧光93菌剂代谢产物中含有抑制全蚀病菌和刺激植株生长的物质。     

Need for flagella for complete virulence of Pseudomonas syringae pv. tabaci: genetic analysis with flagella-defective mutants ?fliC and ?fliD in host tobacco plants

The flagellins purified from Pseudomonas syringae pv. tabaci induce a hypersensitive reaction in nonhost tomato cells. To investigate the role of flagella and flagellin in the compatible interaction, we generated two types of flagella-defective mutant. The fliC mutant lost the fliC gene that encodes flagellin protein, whereas the fliD mutant lost the fliD gene that encodes HAP2-capping protein. The two mutants had markedly reduced ability to cause disease symptoms in tobacco leaves. Furthermore, propagation of the mutants in tobacco leaves was less than that in wild-type pv. tabaci. Compared to the inoculation with wild-type pv. tabaci, inoculation with the two mutants did not markedly induce the expression of typical defense response-related genes such as PAL and hsr203J. Complementation of each fliC and fliD gene to the corresponding deficient mutant restored motility and virulence. These results indicate that flagella of P. syringae pv. tabaci are indispensable organelles for complete virulence on host tobacco plants.     

Isolation and characterization of Pseudomonas aeruginosa from sheep with fleece rot in northern and middle Jordan

A total of 162 sheep fleece samples were collected from 2315 sheep clinically examined for evidence of dermatitis. The sheep belonged to 32 flocks raised in northern and middle Jordan. Eighty-three samples showed no obvious abnormalities, whereas the remainder showed exudation (79 samples), fleece discoloration (18) and fleece roughness (40) and abscesses (7). Seventeen Pseudomonas aeruginosa isolates were obtained from these samples. Antibacterial resistance in vitro was common; resistance to tetracycline, amoxycillin, erythromycin and cotrimoxazole was shown by > 90% of the isolates. Resistance to norfloxacin (29.4% of isolates), ciprofloxacin (17.6%) and amikacin (17.6%) was also demonstrated. Fourteen isolates were serum resistant when assessed after 1-3 h incubation in sheep and calf sera, and their count increased by 2-2.9 and 2.5-3.5 respectively.     

The potential of nonpathogenic Fusarium oxysporum and other biological control organisms for suppressing fusarium wilt of banana

The aim of this study was to evaluate the ability of nonpathogenic F. oxysporum and Trichoderma isolates from suppressive soils in South Africa to suppress fusarium wilt of banana in the glasshouse. Several biological control agents and commercial biological control products were included in the study. The isolates were first screened in vitro on potato dextrose agar. In glasshouse evaluations, the fungal and bacterial isolates were established on banana roots before they were replanted in pathogen-infested soil, while the commercial biocontrol agents were applied as directed by the supplier. Banana plantlets were evaluated for disease development after 7 weeks. In vitro tests showed none of the nonpathogenic isolates suppressed Fusarium oxysporum f.sp. cubense ( Foc ), while slight suppression was observed with the two Trichoderma isolates. Results of the glasshouse evaluations revealed that two of the nonpathogenic F. oxysporum isolates, CAV 255 and CAV 241, reduced fusarium wilt incidence by 87·4 and 75·0%, respectively. The known biological control agent Fo47 did not suppress Foc significantly. Pseudomonas fluorescens strain WCS 417, known for its ability to suppress other fusarium wilt diseases (WCS 417), reduced disease incidence by 87·4%. These isolates should be further evaluated for potential application in the field, independently and in combination.     

Pseudomonas sp.20#-5防治烟草黑胫病田间试验初报

20^#-5菌株是本实验室从土壤中分离保存的1株假单胞菌,2006年对其发酵液防治烟草黑胫病进行了田间防效试验。结果显示,不同发病时期20^#-5菌发酵液的防治效果在64.39%～79.70%,高于对照药剂,防治效果较好。不同施药时期调查结果表明,发病前施用20^#-5菌发酵液的防治效果要好于发病后施用,说明20^#-5菌发酵液对烟草黑胫病具有有效的预防作用。     

Genetic characterization by fluorescent AFLP of Pseudomonas savastanoi pv. savastanoi strains isolated from different host species

The genetic diversity of 71 Pseudomonas savastanoi pv. savastanoi strains isolated from different host species and from diverse geographical regions was determined by fluorescent amplified fragment length polymorphism (f-AFLP) analysis. The study was carried out using three different selective primer combinations. Strains of P. syringae pv. syringae , P. syringae pv. phaseolicola , P. syringae pv. glycinea , P. syringae pv. tagetis and P. amygdali were also included as outgroups. Based on cluster analysis of f-AFLP data, all P. savastanoi pv. savastanoi strains showed a high degree of similarity, grouping in a cluster and forming a taxon clearly separate from outgroup strains. AFLP analyses failed to support placing strains of P. savastanoi pv. savastanoi , P. syringae pv. phaseolicola and P. syringae pv. glycinea in the same species. Strains of P. savastanoi pv. savastanoi formed subclusters that correlated with the host species. Strains identified within these subclusters were related to the geographical region where the strains were isolated. Strains of P. savastanoi pv. savastanoi from olive were divided into two subclusters. Strains from oleander were differentiated from those from ash and were divided into two additional subclusters, distinct from olive strains. Three strains isolated from jasmine showed a high level of similarity among them but, at a lower Dice similarity coefficient, were linked to a subcluster including olive strains. Finally, two strains isolated from privet were similar to strains from olive and were included in the same subcluster.     

Phenotypic variability in different strains of Pseudomonas syringae subsp. savastanoi isolated from different hosts

One hundred and sixty strains of Pseudomonas syringae subsp. savastanoi from Olea europaea, Olea europaea var. sylvestris, Nerium oleander, Fraxinus angustifolia and Retama sphaerocarpa, and four type strains of other pathovars were studied, investigating 102 phenotypic traits, among which we include biochemical characteristics, assimilation of different carbon sources, sensitivity or resistance to antibiotics and indoleacetic acid (IAA) production. Results were analysed with an affinity dendrogram via the Jaccard coefficient. They indicate an influence of environmental factors on the formation of the 15 phenons obtained, since isolated (knot) strains from the same species but different geographical areas are segregated. Segregation, also detected in strains from different hosts within the same area, added to the pathogenicity test helps to characterise these strains as different pathovars.     

Leaf necrosis and twig dieback of sweet persimmon (Dyospiros kaki L.) caused by Pseudomonas syringae pv. syringae in Italy

In spring 1996, extensive leaf necrosis and twig dieback were observed on young sweet persimmon (Dyospiros kaki L.) trees, cultivars O'Gosho, Hachija, Mercatelli and Kaki-tipo planted in the Abruzzo region (central Italy). Many trees were killed. When the dieback reached the trunk, in many cases, new vegetation was noticed above the graft point. The cultivar Jiro-C was not affected by the disease. During 1997, no symptoms were observed on any plant. The orchard was planted in a clay soil with a very low content of organic matter. Biochemical, nutritional and pathogenicity tests indicated Pseudomonas syringae pv. syringae van Hall as the causal agent of the disease. This is the first report of this bacterium as a pathogen of sweet persimmon in Europe.     

木麻黄青枯菌的根表吸附及根内增殖与其致病性关系

对 3个不同致病的青枯菌菌株和 7个不同抗病性的木麻黄无性系苗的研究得出 ,各菌株对寄主根表吸附量具有显著差异 ,吸附量与致病性呈负相关 :各菌株在寄主根内的增殖量差别明显 ,增殖量与致病性呈正相关。病菌脂多糖 (LPS)对幼苗根的预处理 ,可使其供体菌的吸附量减少5 8.5 %　 97.3% ,但胞外多糖 (EPS)对供体菌的吸附量无明显影响。洗去EPS和LPS的菌体较完整菌体对根表的吸附量减少 6 3.3%　 74 .2 %。而仅洗去EPS的菌体对根表的吸附有所增加 ,最高达19.1%。各菌体SDS PAGE电泳图谱显示出一定差异 ,其中强毒菌株 6 0 1B具有Rf=0 .35的特异谱带。结果表明青枯菌对木麻黄的致病性与其在寄主根表的吸附情况和在根内的快速增殖具有密切关系。LPS在此病理系统中 ,起着细菌识别因子的作用 ,EPS对LPS进行掩盖 ,二者都是病菌致病性的重要因子