紫茎泽兰根际土壤中优势细菌的筛选鉴定及拮抗性能评价

采用分离培养的方法，从紫茎泽兰根际土壤中筛选鉴定了优势细菌25株，并测定了其中8株优势细菌及其代谢产物对病原菌的拮抗性能．结果表明：紫茎泽兰根际土壤中存在着丰富的芽孢杆菌和假单胞菌，其中枯草芽孢杆菌和巨大芽孢杆菌数量最多，占鉴定细菌总数的55．6％；这些优势细菌类群对番茄枯萎病菌和青枯病菌有不同程度的拮抗作用，以枯草芽孢杆菌BS-5和苏云金芽孢杆BT-1对番茄枯萎病菌的拮抗效果最为明显，其代谢产物的抑菌率分别为85．5％和83．8％；优势细菌代谢液比菌体对病原菌的拮抗作用更强．紫茎泽兰根际丰富的具有强拮抗性能的细菌类群可能是紫茎泽兰不受土传病害侵扰的原因，也是其逃避天敌的重要手段；通过这种根际有益微生物的反馈作用，紫茎泽兰在与当地植物竞争中直接或间接地处于有利地位，从而有利于其排挤当地植物，迅速扩张蔓延．

Screening,identification,and antagonism assessment of dominant bacteria in Ageratina adenophora Sprengel rhizosphere soil

By using isolation and culture method, 25 strains of dominant bacteria in Ageratina adenophora rhizosphere soil were isolated and identified, of which, 8 strains were assessed for their antagonistic activity. The results showed that Bacillus and Pseudomonas were highly abundant in A. adenophora rhizosphere soil, of which, B. subtilis and B. megaterium were most abundant and occupied 55.6% of the total identified bacteria. These dominant bacteria had different level antagonistic activity to Fusarium oxysporum and Ralstonia solanacearum, and B. subtilis BS-5 and B. thuringiensis BT-1 had the strongest antagonistic effect on F. oxysporum, with the antagonistic activity of their metabolic products being 85.5% and 83.8%, respectively. The metabolic products of the dominant antagonistic bacteria had even more stronger antagonistic effect on pathogens than the soil-borne diseases and escape its natural enemies. Through the feedback actions of the beneficial rhizosphere microbes, A. adenophora probably earned its competition superiority directly or indirectly, being favorable to its rapid expansion.