2株桃树根际细菌Alcaligenes faecalis对根癌病的抑制作用

Suppression effect of two peach rhizobacteria Alcaligenes faecalis on crown gall disease caused by Agrobacterium tumefaciens

【目的】筛选拮抗根癌病的生防细菌,为根癌病的生物防治提供材料。【方法】采用平板拮抗法测定桃树根际、茎和土壤中细菌对根癌土壤杆菌Agrobacterium tumefaciens的拮抗活性;以向日葵和番茄为感病植物,测定拮抗菌的防病效果;通过形态特征、生理生化特性和16S r DNA序列分析,明确高效生防菌的分类地位。【结果】利用平板拮抗法从125株桃根际细菌中,筛选出2株可在YEB培养基平板上产生抑菌圈的拮抗菌株51-A和51-B和5株没有抑菌圈但长势良好的菌株。将浓度为106cfu·m L-1的待测菌的菌悬液和A.tumefaciens菌悬液以10∶1的比例混和接种向日葵7 d后,菌株51-A和51-B可显著抑制根癌瘤的形成,防效分别为98.0%和97.0%;提前接种拮抗菌菌悬液,第2天接种病原菌菌悬液,可明显抑制番茄根癌瘤的形成,防效分别为91.9%和86.5%。通过形态特征、生理生化特性和16S r DNA序列分析,将51-A和51-B归为粪产碱菌A.faecalis。【结论】粪产碱菌A.faecalis 51-A和51-B对A.tumefaciens引起的根癌病具有强烈抑制作用,可用于根癌病的防治。

【Objective】To screen the antagonists for biological control of crown gall disease.【Methods】Bacteria were isolated from healthy peach roots,stem and rhizosphere soil. Their antagonisms against thecausal agent of crown gall disease,Agrobacterium tumefaciens,were tested by using pair co-culturingmethod. The efficacy of the antagonists in suppressing crown gall disease was further evaluated in green-house using sunflowers and tomato seedlings as susceptible plants. Then the antagonists with strong inhib-itory ability were identified by the analysis of their 16 S r DNA sequences in combination with their mor-phologies and biochemical and physiological characteristics.【Results】A total of 125 bacterial strainswere isolated from the roots,stem and rhizosphere soil of healthy peach trees. Among them,two strains51-A and 51-B produced clear zone around the bacterial colony on the YEB plates inoculated with A. tumefaciens,and five of them grew well without clear zones around the colonies. The ability of strains 51-Aand 51-B to inhibit the crown gall formation was further tested by inoculating the stems of sunflower withcell suspensions of each candidate bacterium and 106 cfu m L-1A. tumefaciens(v∶v=10∶1). After one week growth at 28 ℃ in greenhouse,strains 51-A and 51-B showed good performance in disease control withthe efficacy of 98.0% and 97.0%,respectively. Further test in tomato seedlings by one day pre-drenchingwith antagonistic bacterial cell suspension followed by drenching A. tumefaciens confirmed the suppres-sion ability of 51-A and 51-B against A. tumefaciens with the control efficacy of 91.9% and 86.5%,re-spectively. Strains 51-A and 51-B were then identified to be A. faecalis by their 16 S r DNA sequences incombination with their morphologies and biochemical and physiological characteristics. 【Conclusion】Crown gall disease caused by A. tumefaciens could be effectively suppressed by two peach rhizobacteria A.faecalis which have a great potential for future application in management of crown gall disease.