弯曲平脐蠕孢拮抗细菌的筛选、鉴定及拮抗作用

【背景】玉米弯曲平脐蠕孢是引起玉米叶斑病的主要病原,严重危害农业生产。利用细菌防治弯曲平脐蠕孢是目前研究的热点。【目的】筛选对玉米弯曲平脐蠕孢有高拮抗性的菌株,对其进行鉴定并探究其拮抗机制。【方法】采用平板对峙法,从玉米田地表下土壤分离获得22株细菌,再经过复筛得到一株对玉米弯曲平脐蠕孢具有较高拮抗活性的菌株L-14。【结果】筛选发现,菌株L-14对层出镰孢(Fusariumproliferatum)、禾谷镰孢(Fusariumgraminearum)、大斑凸脐蠕孢(Exserohilum turcicum)、弯曲平脐蠕孢(Bipolaris papendorfii)和灰霉病菌(Botrytis cinerea) 5种植物病原真菌均有抑制作用,是一株广谱拮抗作用的生防菌株。通过对该菌株进行形态观察、16S rRNA基因序列分析以及生理生化特性检测,鉴定其为枯草芽孢杆菌。对菌株L-14的抗菌机制进行研究,发现该菌发酵液的蛋白粗提物对弯曲平脐蠕孢气生菌丝形态无影响,但可致基内菌丝畸变,对弯曲平脐蠕孢分生孢子萌发有抑制作用。【结论】筛选的拮抗菌在防治植物病害上具有广谱性及较高的拮抗活性,能有效防治玉米叶斑病。

Isolation, identification and characterization of an antagonistic bacterium against Bipolaris papendorfii

Background] Bipolaris papendorfii is the main fungal pathogen of Curvularia leaf spot, and harmful to agricultural production. At present, the use of bacteria to control B. papendorfii becomes research focus in this field. Objective] To screen the strains with high antagonistic activity against B. papendorfii, and identify the antagonistic mechanism. Methods] Twenty-two bacterial strains were isolated from the soil under the surface of corn field by the method of plate confrontation. One strain L-14 with high antagonistic activity to B. papendorfii was obtained by repeated screening. Results] Strain L-14 with the highest antagonism was obtained by using the plate diffusion method. After morphological observation, 16S rRNA gene sequence analysis, physiological and biochemical characteristics detection, the strain was finally identified as Bacillus subtilis. Moreover, the strain is a wide-spectrum antagonistic biocontrol strain with inhibitory effects on Fusarium proliferatum, Fusarium graminearum, Exserohilum turcicum, Bipolaris papendorfii and Botrytis cinerea. Then, we studied the antibacterial mechanism of strain L-14 and obtained that the fermentation crude protein extracts had no effect on the morphology of the aerial hyphae of B. papendorfii but can cause the mycelial aberration, and had an inhibitory effect on spore germination. Conclusion] The antagonistic bacterium B. subtilis obtained in this study has broad spectrum and high antagonistic activity in the control of plant diseases, and can effectively control Curvularia leaf spot.