Abstract:

Cercospora leaf sport of beet （CLS）， caused by Cercospora beticola， is the most destructive foliar fungal disease of sugar beet worldwide which seriously restricts the development of China’s sugar industry. In order to screen and identify the antagonistic strains with biocontrol applications against Cercospora beticola， the rhizosphere soil samples of sugar beet were collected from Hulunbuir， Inner Mongolia autonomous region and the antagonistic strain HM85 with stable antimicrobial activity was screened by dilution coating flat plate method and dual culture assay. The strain HM85 was identified as Streptomyces rochei based on its morphological，physiological and biochemical characteristics along with 16S rRNA gene sequence analysis．The results of dual culture test showed that the HM85 strain could significantly inhibit the growth of Cercospora beticola HB2-2-2 with inhibitory rate of 58.68%. In addition， the fermentation broth of S. rochei HM85 had antagonistic activity against Cercospora beticola and could promote the growth of sugar beet in pot tests，which plant height， fresh weight of plant，root length，fresh weight of root and root diameter was increased by 22.73%， 20.47%， 36.10%， 32.52%， 75.03% compared to the control， respectively. In summary， S. rochei HM85 could be exploited as a potential bio-inoculant improving production and biocontrol agent for sugar beet leaf sport disease control.

Key words: Streptomyces rochei, Cercospora beticola, Cercospora leaf sport of beet （CLS）, antagonistic activity, growth-promoting effect

摘要：

由甜菜尾孢菌（Cercospora beticola）引起的甜菜褐斑病是一种广泛发生、危害严重的真菌性病害，严重制约了我国糖料产业的发展。为挖掘对甜菜褐斑病具有生防应用潜力的拮抗菌株，从内蒙古自治区呼伦贝尔黑土地采集甜菜健康植株根际土壤样本，通过梯度稀释平板法和对峙培养法进行分离、纯化、筛选，获得1株具有良好拮抗效果的菌株HM85。基于其形态学特征和生理生化特征，结合16S rRNA基因序列分析将菌株HM85鉴定为娄彻氏链霉菌（Streptomyces rochei）。平板对峙试验结果显示，菌株HM85对甜菜尾孢菌HB2-2-2菌株的生长有明显抑制作用，抑菌率为58.68%。盆栽试验结果表明，HM85在防治甜菜褐斑病的同时对甜菜植株具有一定的促生作用，株高、株鲜重、根长、根鲜重和根直径与对照组相比分别增加22.73%、20.47%、36.10%、32.52%和75.03%。由此可见，娄彻氏链霉菌HM85具有作为促生菌剂和生防菌剂的研发潜力。

关键词: 娄彻氏链霉菌, 甜菜尾孢菌, 甜菜褐斑病, 拮抗活性, 促生作用