烟草黑胫病拮抗内生细菌的分离、鉴定及防效测定

Isolation,identification and control efficacy determination of an endophytic strain against Phytophthora parasitica var.nicotianae

采用常规分离方法从健康烟株的根、茎、叶中分离得到内生细菌269株,从中筛选出7株对烟草黑胫病病原菌具有明显拮抗作用的菌株,它们的抑菌半径达到6 mm以上。菌株05-4004、05-2501培养液滤液中存在具有明显抑菌作用的活性成分。致病性试验中,发现菌株701-1在人工接种条件下有致病能力或潜在致病性,选择余下6株拮抗细菌进行了温室盆栽试验,以05-4004、05-2002两株烟草内生细菌对烟草黑胫病的防效最好,分别为46.6%、45.2%。促生试验中,NB培养液和清水对照的种子发芽率分别为84.3%、82.7%,而经过05-2002和05-4004除菌滤液浸种后,发芽率分别提高到93.5%和93.7%。经过05-4004、05-2002灌根处理后,株高、叶长、叶宽、有效叶片数、叶面积明显增加。证明菌株05-2002、05-4004同时还具有一定的促生作用。以细菌16S rDNA同源性为基础的系统发育分析表明05-4004和Bacillus pumilus(EU366363)、Bacillus safensis(AY030327)处于同一分支,相似性为100%,05-4004鉴定为芽孢杆菌属。

269 endophytic bacteria were isolated from healthy tobacco plant with conventional isolation method. Seven strains that obviously antagonized against growth of P. parasitica var. nicotianae were screened, all with above 6ram width of inhibitory zone. Antagonistic activity test showed that there existed some antagonistic substances in the culture filtrates for strain 05-4004 and 05-250l. Pathogenic test showed that strain 701-1 exhibited obvious or potential pathogenicity to tobacco after inoculation, Other 6 strains were tested with greenhouse experiment and results showed that strain 05-4004 and 05-2002 were the most effective strains against P. parasitica var nicotianae with control efficacy of 46.6% and 45.2%. Germination rates of tobacco seeds in NB culture and untreated seeds were 84.3% and 82.7%, respec- tively, while seeds soaked in strain 05-2002 and 05-4004 culture were improved to 93.5% and 93.7%. Plant height, leaf length, leaf width and number of leaves were effectively increased when roots were irrigated with strain 05-2002 and 05-4004 culture. Phylogentic analysis based on 16S rDNA suggested that 05-4004 shared 99% homologies with Bacillus pumilus （EU366363） and Bacillus safensis （AY030327）. These sequences constituted a branch in phylogenetic tree.