黄瓜菊苣假单胞菌叶斑病内生拮抗细菌的鉴定及促生作用

Isolation and screening of endophytic antagonistic bacteria against cucumber leaf spot Pseudomonas cichorium and its growth promotion effect

从湖南、云南、海南等地采集的健康黄瓜植株中分离得到189株内生细菌,从中筛选的内生细菌Y–10对黄瓜叶斑病病原菌菊苣假单胞菌(Pseudonwnas cichorii)的抑菌半径达16 mm,拮抗效果最好,经形态学、生理生化特性及16S rDNA和rpoA双基因联合建树分析,被鉴定为枯草芽孢杆菌(Bacillus substilis)。分别用4×10^(9)、4×10^(8)、4×10^(7)、4×10^(6)、4×10^(5) cfu/mL的Y–10菌液浸黄瓜种子和4×10^(9)、4×10^(8)、4×10^(7)、2×10^(7)、4×10^(6) cfu/mL的菌液灌根处理黄瓜盆栽幼苗,以无菌水浸种和灌根处理作为空白对照。结果显示,Y–10菌液4×10^(7) cfu/mL处理的种子发芽率较空白对照提高了6.01%,菌液4×10^(9) cfu/mL处理的种子几乎不萌发;黄瓜幼苗的根长、根鲜质量、地上部鲜质量、地上部干质量分别提高了40.71%、33.59%、35.21%、58.18%。4×10^(9) cfu/mL菌液灌根接种后,黄瓜幼苗根长、根鲜质量、地上部的鲜质量和干质量分别较空白对照提高了11.49%、19.57%、77.25%、47.15%。Y–10菌株无溶磷、解钾及产IAA作用,但具固氮、产铁载体的作用。

One hundred and eighty-nine endophytic bacteria strains were isolated from healthy cucumber plants collected from Hunan,Yunnan and Hainan.The inhibitory radius of strain Y-10 to Pseudomonas cichorium,the pathogen of cucumber leaf spot,was 16 mm,and the antagonistic effect was the best.The strain Y-10 was identified as Bacillus subtilis by combining the results of morphological,physiological and biochemical characteristics and 16S rDNA and rpoA genes analysis.Bacterial suspensions of strain Y-10 was diluted to 4×10^(9),4×10^(8),4×10^(7),2×10^(7),4×10^(6),4×10^(5) cfu/mL by gradient dilution,and 4×10^(8),4×10^(7),4×10^(6),4×10^(5) cfu/mL suspensions were selected to soak seeds separately,while 4×10^(9),4×10^(8),4×10^(7),2×10^(7),4×10^(6) cfu/mL solutions were used to irrigate seedlings independently.Sterile water soaking and root irrigation were used as blank controls.The results show that some dilutions of strain Y-10 could promote the cucumis seedling growth and seeds germination.After soaking seeds with 4×10^(7) cfu/mL bacterial solution,the germination rate of seeds was 6.01%higher than that of the blank control.The seeds hardly germinated when treated with 4×10^(9)cfu/mL bacterial solution,and the root length,root fresh weight,shoot fresh weight and shoot dry weight of cucumber seedlings increased by 40.71%,33.59%,35.21%and 58.18%respectively.In the treatment with 4×10^(9)cfu/mL bacterial solution irrigation,the root length,root fresh weight,shoot fresh weight and shoot dry weight of cucumber seedlings,compared with the blank control,were increased by 11.49%,19.57%,77.25%and 47.15%,respectively.Strain Y-10 had no function of dissolving phosphorus and potassium and producing IAA,but had the function of fixing nitrogen and producing iron carrier.