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为了筛选对小麦纹枯病菌具有生防作用的菌株，从西藏米林县采集的砂生槐根瘤中分离到45 株内生细菌，采用平板对峙法、菌丝生长速率法进行拮抗菌株筛选，用显微观察法研究受抑制病原菌菌丝变化；通过摇瓶培养法测定所筛选拮抗菌株的溶磷、固氮及分泌IAA功能，并对其进行盆栽接种防效试验；依据形态观察、生理生化反应及16S rDNA序列同源性分析确定所筛选菌株系统发育地位。结果表明，经过初筛和复筛，45 株内生菌中，菌株R4对小麦纹枯病菌的拮抗效果较明显，对其抑菌圈直径达20.5 mm，抑菌率达98.2%，显著推迟菌核的萌发。受R4作用的小麦纹枯病菌菌丝末端分枝增多、部分原生质浓缩、形成瘤状结。菌株R4抗菌谱广，具有溶磷、固氮和分泌IAA活性。盆栽防效试验中，经菌株R4发酵液处理后，小麦纹枯病发病率和病情指数均显著降低，防治效果最高达73.82%。通过形态、生理生化特性及16S rDNA 基因序列同源性比对分析，该菌株被鉴定为土地类芽孢杆菌Paenibacillus terrae。

英文摘要:

Forty-five endophytic bacteria were isolated from root nodules of Sophora moorcroftiana collected at Milin County in Tibet and were screened for inhibitory effect on Rhizotonia cerealis,by means of flat plate confrontation method and mycelial growth rate method. For bacterial strains with remarkable inhibitory effect to R.cerealis,morphological changes of hyphae of the fungus was observed by microscopy. Antimicrobial spectrum and inhibition of endophytic bacteria to sclerotia of R.cerealis were tested using the flat plate confrontation method. Using inoculation of fresh bacteria,determination of phospholysis,nitrogen fixation,secretion of IAA of the strain were conducted using flask culture method. Biological species of the strain was identified by morphological observation,physiological biochemical reaction and 16S rRNA gene sequence analysis. The results indicated that the strain R4 of 45 strains of endophytic bacteria presented obvious inhibitory effect against R.cerealis based on the primary screening and re-screening tests,showing an inhibitory circle of 20.5 mm in diameter to R.cerealis an inhibition rate of 98.2% and a significant delay on germination of sclerotia of the fungus. Hyphae of R.cerealis treated with fermentation liquid increased branches at the end of hyphae. A part of protoplasm concentrated to form nodules. The strain R4 has a wide antibacterial spectrum,a capacity of phospholysis,nitrogen fixation and IAA secretion. The potted experiment tests showed that incidence and disease indices of R.cerealis were significantly reduced after treated with fermentation liquid of strain R4,representing a control effect of 73.82%. Through homology observation,physiological and biochemical analyses of the strain R4,combined with sequence comparison of the 16S rRNA gene,the strain was identified as Paenibacillus terrae.

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