一株西瓜枯萎病生防菌的鉴定与田间防效

Identification and field control effect of an antagonistic bacterium against watermelon Fusarium wilt

摘要:

【背景】西瓜枯萎病是由尖孢镰孢菌西瓜专化型(Fusarium oxysporum f. sp. niveum)引起的土传病害，是西瓜最为严重的病害之一。利用拮抗微生物抑制病原菌繁殖，降低其危害程度，已成为西瓜枯萎病防控领域的研究热点。【目的】筛选对西瓜枯萎病病原菌具有拮抗作用的菌株，并探究其抑菌作用，为有效防控西瓜枯萎病提供生防资源。【方法】从西瓜的根围土中分离细菌，采取平板对峙及温室生测的方法筛选生防菌，通过形态学及gyrB基因序列同源性分析对生防菌株进行鉴定；采用鉴别性培养基测定生防菌的拮抗因子(纤维素酶、蛋白酶、几丁质酶、β-1,3-葡聚糖酶)；测定生防菌发酵液对西瓜枯萎病菌孢子萌发及菌丝生长的影响；于田间条件下检测该菌株防治西瓜枯萎病的效应。【结果】筛选到了一株对西瓜枯萎病具有防治效果的拮抗菌株SFJ11，经鉴定该菌株为解淀粉芽胞杆菌(Bacillus amyloliquefaciens)。该菌株可以分泌蛋白酶和纤维素酶，其20%的发酵液几乎能完全抑制西瓜枯萎病菌菌丝的生长，对孢子萌发的抑制率为95%，田间防治效果最高可达78%。【结论】菌株SFJ11对西瓜枯萎病具有较强的生防效果，有潜在的应用价值。

关键词:西瓜枯萎病，生防菌，解淀粉芽孢杆菌，拮抗因子，生物防治

Abstract:

[Background] Watermelon Fusarium wilt is a soil-borne disease caused by Fusarium oxysporum f. sp. niveum, and one of the most serious diseases in watermelon production. Identification of antagonistic microorganisms is necessary to develop biocontrol agents. [Objective] To isolate and identify effective biocontrol strains against watermelon Fusarium wilt, and investigate the inhibitory effect, ultimately provide candidates for developing biocontrol agents. [Methods] We isolated bacteria from the rhizosphere soil of watermelon. Antagonistic bacteria were screened by plate confrontation and greenhouse bioassay method. Morphological observation and gyrB gene sequence homology analysis were performed to characterize the strains isolated. The antagonistic factors (cellulase, protease, chitinase, β-1,3-glucanase) of antagonistic bacteria were determined by differential medium, and the effects of antagonistic bacteria fermentation liquid on the spore germination and hypha growth of Fusarium oxysporum f. sp. niveum were determined. Finally, the control effect of antagonistic bacteria on watermelon Fusarium wilt was determined in the field. [Results] An antagonistic strain SFJ11 against watermelon wilt was selected by means of plate confrontation and greenhouse assay. The strain was identified as Bacillus amylolyticus by morphological identification and homology analysis of gyrB gene sequence which could secrete protease and cellulase. The 20% fermentation broth of antagonistic bacterium SFJ11 could almost completely inhibit the growth of mycelia, and inhibit the germination of 95.44% of spores of Fusarium oxysporum f. sp. niveum. The control effect of SFJ11 on watermelon Fusarium wilt was 78% in field experiment. [Conclusion] Strain SFJ11 had a notably biological control effect on watermelon Fusarium wilt, and it would be a potential biocontrol agent.

Key words:watermelon Fusarium wilt, antagonistic bacteria, Bacillus amyloliquefaciens, antagonistic factor, biological control