中文摘要：

为获得对黄芪根腐病具有强抗菌活性的生防菌株,采用平板对峙法、抑制菌丝生长速率法对分离于河西走廊盐碱土中的172株放线菌进行拮抗菌的筛选,获得优菌株DA4-4-1,根据其形态、培养特征、生理生化特性和16S rDNA基因序列进行系统发育学分析鉴定,并根据单因素试验与正交试验对培养基条件进行优化。结果表明,菌株DA4-4-1对黄芪根腐病的2种主要致病菌尖孢镰刀菌Fusarium oxysporum和茄腐镰刀菌F.solani均有较好的抑制作用,抑菌圈直径最大分别为20.16 mm和19.33 mm,抑菌率最大分别为34.62%和32.44%。结合16S rDNA基因序列的系统发育分析,将菌株DA4-4-1鉴定为链霉菌属蓝紫链霉菌Streptomyces tuirus。培养基最佳碳源为麦芽糖,氮源为（NH_4）_2SO_4,其优化条件为麦芽糖15 g/L、（NH_4）_2SO_4 0.5 g/L、NaCl 10 g/L、pH 7,在此条件下菌株DA4-4-1的抑菌率可达到86.72%。表明菌株DA4-4-1是1株具有较强抗菌活性的放线菌,具有良好的生物防治和开发应用潜力。

英文摘要：

In order to get antagonistic microbes with strong antifungi activity on Astragalus membranaceus root rot disease,strain DA4-4-1 was screened from 172 actinomycetes which isolated from saline-alkali soil in the Hexi Corridor using plate-confrontation and growth speed rate methods in vitro.Strain DA4-4-1 was identified by cultural characteristic,physiological,biochemical characteristics and 16S rDNA sequences phylogenetic analysis,and the growth medium conditions was optimized by single factor and orthogonal test.The result showed that strain DA4-4-1 had obvious inhibition to A.membranaceus root rot caused by pathogenic Fusarium oxysporum and F.solani with the maximal inhibition diameter of 20.16 mm and19.33 mm,and the highest inhibition rate of 34.62%and 32.44%respectively.Based on the combination of the morphological,physiological and biochemical characteristics and 16S rDNA sequence analysis,the strain DA4-4-1 was identified as Streptomyces tuirus.The optimum carbon source was maltose,and the optimum nitrogen source was（NH_4）_2 SO_4.The optimum culture conditions obtained through orthogonal experiment were with a medium of maltose 15 g/L,（NH_4）_2 SO_4 0.5 g/L,NaCl 15 g/L,pH 7,and inhibition rate of strain DA4-4-1 to pathogen reached to 86.72%under this condition.The results indicated that the strain DA4-4-1 had a strong inhibition activity to the disease of root rot on A.membranaceus,and provide a new antifungal agent for controlling the pathogen of F.oxysporum on A.membranaceus.