Using dual culture method and dilution separating methods,53 strains of antagonistic bacteria on Ascochyta citrullina were obtained in 48 soil samples.Among the tested bacterial strains,only strains G8 and Sh34 showed strong and stable antagonistic activities against A.citrullina.in the present test,strains G8 and Sh34 inhibited the growth of ten plant pathogenic fungi.The extent of inhibition of A.citrullina and Sclerotinia scleotiorum reached over 76%.The two strains were shown to produce chitinase.Pot trials in greenhouse showed that effects of the fermentated broth of G8 and Sh34 strains against cucumber gummy stem blight disease reached 62.5% and 51.0%,respectively.On the basis of their morphological and biochemical characteristics as well as analysis of the partial sequence of their 16SrDNA,G8 and Sh34 were identified as Bacillus subtilis strains.
The article briefly summarized the characteristic of the humoral and cell-mediated immunity of ducks,and reviewed the progress of Riemerella anatipestifer vaccine research and development and its'efficiency test methods.
In greenhouse, the cotton (cv.Simian 3) seedling roots were treated by different concentrations of propyl dihydrojasmonate (PDJ) varying from 1 to 50 mg·L~(-1). Two days after the treatment, cotton gained resistance to cotton Verticillium wilt and the concentration of 10 mg·L~(-1) was more effective. The Phenylalanine amonnia lyase (PAL) activity of cotton seedlings pretreated by 10 mg·L~(-1) PDJ and inoculated with Verticillium dahiliae increased significantly compared with those water-treated within 7 days. Meanwhile, increment of lignin content, Peroxidase (POD) activity and MDA content were also observed in PDJ-treated and inoculated with Verticilluim dahiliae leaves. These changes coincide with the expression of PDJ-induced resistance exactly. Thus, the increment of lignin, MDA content and activities of PAL and POD were considered to be involved in the biochemical mechanisms of PDJ-induced resistance of cotton seedling to Verticillium dahliae.
An antagonistic bacterium strain BSH-4 was isolated from rhizosphere soil of cucumber in the greenhouse.Dual culture test indicated that the strain was highly inhibitory to Sclerotinia sclerotiorum by making the mycelium swollen and curly,the protoplasm inside brown and concentrated,and the production of sclerotium delayed.Treat with fermentation broth of BSH-4,the disease control efficacy was 81.6% on detached leaves test,and 68.3% on pot trials.And the recovering rate was attained to 74.4% when sclerotial blight infected stems of cucumber was treated in the field.All the efficacies of BSH-4 broth excelled that of dimethachlon fungicide.The fermentation broth of BSH-4 had no impact on seed germination rate,but also promoted the growth of cucumber seedling.Identification by morphological observation,physiological and biochemical determinations,and 16S rDNA sequences analysis showed that the strain was belonged to Bacillus pumilus.
Botulism is a potentially lethal paralytic disease caused by botulinum neurotoxin,correct and rapid diagnosis is essential for therapy.This paper reviewed the current advance of the laboratory diagnostics of botulism including detection of botulinum neurotoxin,culture methods,molecular detection and genetic characterization of Clostridium botulinum.
Plant-parasitic nematode Ditylenchus destructor is one of the most serious pathogens of crops and vegetables.In this study,volatiles produced by two Bacillus subtilis strains BL02 and G8 both displayed 100% nematicidal activity(NA) against D.destructor in sealed dishes.When exposed to these nematicidal volatiles,the nematodes gradually reduced movement within 1-12 h and stopped completely after 24 h.The effective volatiles were extracted using solid-phase micro-extraction(SPME) and further identified by gas chromatography-mass spectrometry(GC-MS) technique.The detected volatile organic compounds(VOCs) included alkyls,alcohols,esters,ketones,acid,amine,oxime,phenols and heterocyclic compounds.This study provided useful information for the exploitation of microbial bioactive volatiles and was the first report about the potential application of bacterial volatiles in biocontrol of plant-parasitic nematode.
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