Study On Screening Antagonistic Actinomycetes Against Tomato Bacterial Wilt

Two hundred and sixty five strains of actionmycetes were isolated from 46 soil samples collected from various areas with different vegetations in Guangxi. Seventy three strains, which showed antagonistic activity against Ralstornia solanacearum, were obtained by means of inhibition zone. Strain St-145 was identified as Streptomyces lavendulae Waksman & Curtis according to its morphological, cultural, physiological and biochemical characteristics, the analysis of the chemical components in its cell wall and 16S rDNA sequence analysis.For the growth of the strain, the optimum pH and temperature were 10.0 and 32℃, respectively. It could use many carbons as carbon source, such as sucrose glucose hydrate,fructose,raffinose,rhamnose,ribose,glycerin, maltose and mannitol,but it could not use inositol as carbon source.Production of antagonistic substance by the strain was considered as one of its antagonistic mechanisms against R.solanacearum. Cultured in different media, the antigonistic substance produced by strain St-145 had different inhibitive effects on R.solanacearum. Of 10 media, the sixth media was the best media for the strain to produce antagonistic subtance. The crude antagonistic substance produced by the strain showed strong inhibition against R.solanacearum, the inhibitory diameter against the pathogen was 15.67 mm.The crude antagonistic substance was stable to pH but sensitive to heat. The water solubility and ion character of the antagonistic substance were analysized by Jack's eight solvents system paper chromatography and pH paper chromatography. The result showed that the antagonistic substance had strong polar. Accoding to the result, we could peculate that it was one of water solubility-alkaline antibiotic.The mycelium of strain St-145 and its crude antibiotic showed widespread antimicrobial spectrum. They could inhibit not only bacteria and yeast, but also fungi, such as Mangnorphe grisea (Cooke)Sacc, Fusarium moniliforme Sheld., Exserohilum turcicum (Pass.) Lenonard & Suggs, Bipolaris maydis (Nishik. & Miyabe) Shoem., Phomopsis sp., Alternaria brassicae (Berk.) Sacc, Alternaria brassicicola (Schw.) Wiltshire,Curvularia lunata (Walker) Boedijin Alternaria musae Bour. et Bat, Alternaria cucumetina (Ell.ct.Ev.)Elliott,...