中文摘要：

从紫花苜蓿根际土中分离出2株芽孢杆菌（Bacillus spp．）菌株CYY-6和CYY-42，并评价了其对尖孢镰刀菌（Fusariurn oxysporurn）的抑制作用，及其对由尖孢镰刀菌引起的苜蓿根腐病的防治效果。经过形态观察、16S rD-NA序列分析和生理生化鉴定，确定菌株CYY-6为地衣芽孢杆菌（Bacillus licheniforrnis），CY-42为短短芽孢杆菌（Brevibacillus brevis）。同时检测发现这2株芽孢杆菌均能不同程度地合成嗜铁素。在平板对峙实验中，2株菌株均能对尖孢镰刀菌产生拮抗作用，并产生抑菌带，抑菌率分别为49．3％和56．3％。且其发酵液可以致使尖孢镰刀菌菌丝及孢子生长异常，出现菌丝扭曲、断裂、破碎，孢子数量明显减少等现象。在盆栽实验中，2株菌株对由尖孢镰刀菌引起的紫花苜蓿根腐病的相对防效分别为57．55％和64．03％，在紫花苜蓿根腐病防治方面具有较好的应用潜力。

英文摘要：

The aims of this study were to identify two Bacillus spp.,CYY-6 and CYY-42,isolated from the rhizosphere of alfalfa,and to evaluate their ability to inhibit Fusarium oxysporum,the causal pathogen of alfal-fa root rot.Based on physiological,biochemical,morphological,and 16S rDNA sequencing analyses,strain CYY-6 was identified as Bacillus licheniformis and CYY-42 as Brevibacillus brevis.Both strains were able to synthesize siderophores,although at different levels.In a dual culture assay,both strains inhibited the growth of F.oxysporum.Based on the inhibition zones,the inhibitory rates of CYY-6 and CYY-42 against F.oxyspo-rum were 49.3% and 56.3%,respectively.The fermentation broth of each strain resulted in deformed growth of the mycelia and spores of F.oxysporum.The mycelia were twisted,broken,or fragmented,and the num-ber of spores was significantly decreased.Strains CYY-6 and CYY-42 showed 57.55% and 64.03% inhibition of alfalfa root rot in pot experiments,indicating that both strains have potential applications in controlling alfal-fa root rot.