一株水稻纹枯菌拮抗细菌的分离与鉴定

Isolation and identification of an antagonistic bacterium against Rhizoctonia solani,the causing agent of rice sheath blight

【目的】从土壤中分离并鉴定水稻纹枯菌拮抗细菌,测定其体外抑菌和温室防治效果。【方法】采用系列稀释法和平板对峙法筛选拮抗细菌,基于形态、生理特征及16S rDNA序列鉴定其分类地位,采用种子细菌化温室试验测定其防效。【结果】从蔬菜根际土壤中筛选出一株纹枯菌拮抗细菌,命名为kwkjT4。菌株具有明显的体外抑菌活性,对水稻纹枯病的温室防效与井冈霉素相当,初步鉴定为假紫色色杆菌(Chromobacterium pseudoviolaceum)。最适生长条件为pH 7.0,温度32°C,培养时间为36 h;抑菌活性物质产生的最适培养条件为pH 6.0,温度28°C,培养时间为48 h;表明两者并不一致。【结论】kwkjT4菌株在水稻纹枯病的生物防治中具有潜在的应用价值。这是C.pseudoviolaceum拮抗纹枯菌的首次报道。

[Objective] This study is aimed to isolate and characterize antagonistic bacteria from soil,and evaluate their in vitro inhibition and control efficacy against Rhizoctonia solani,the causing agent of rice sheath blight in a green house.[Methods] Serial dilution method and dual culture technique on agar plate were used for screening bacteria.Strain identification was based on morphological and physiological characteristics,and phylogenetic analysis of 16S rDNA sequence.Control efficacy against rice sheath blight was evaluated by seed bacteriza-tion tests in a green house.[Results] An antagonistic bacterial strain against Rhizoctonia so-lani was isolated and screened from vegetable rhizosphere soil.The strain,designated as kwkjT4,exhibited excellent in vitro inhibition against the fungal pathogen.Its control efficacy against rice sheath blight was comparable to that of jinggangmycin.It was preliminarily iden-tified as a strain of Chromobacterium pseudoviolaceum.The optimal growth conditions of the strain were as follows： pH 7.0,temperature 32 °C,incubation time 36 h.Inconsistence with those for the bacterial growth,the optimal conditions for accumulating inhibitory substances were pH 6.0,temperature 28 °C,and incubation time 48 h.[Conclusions] Strain kwkjT4 had potentials for the biological control of rice sheath blight.This is the first report on the antago-nism of C.pseudoviolaceum against Rhizoctonia solani.