小麦全蚀病菌拮抗细菌的筛选及生防效果

为筛选小麦全蚀病菌Gaeumannomyces tritici的拮抗细菌，从健康小麦根际土壤中分离和筛选拮抗细菌，采用对峙培养法和室内盆栽试验测定拮抗细菌对小麦全蚀病菌的抑制活性及生防效果，通过形态学特征观察、生理生化特性测定和保守序列分析确定其分类地位。结果表明，从小麦根际土壤中分离并筛选获得2株具有较好拮抗效果的菌株XJ-3和XJ-4，对小麦全蚀病菌菌丝生长的抑制率分别为64.31%和65.25%。基于菌株XJ-3和XJ-4的形态学特征、生理生化特性和gyrB基因系统进化分析结果，将其均鉴定为贝莱斯芽胞杆菌Bacillus velezensis。菌株XJ-3和XJ-4的发酵液中均含有一类具抗真菌活性、耐热性的非蛋白类次生代谢产物；经菌株XJ-3和XJ-4发酵液处理小麦幼苗后，株高较对照分别显著增加了6.48%和13.12%，干重较对照分别增加了1.30%和14.29%，其中菌株XJ-4的促生效果相对较好；对小麦全蚀病的盆栽防效分别达到51.29%和52.46%。表明筛选得到的贝莱斯芽胞杆菌XJ-3和XJ-4可用于小麦全蚀病的生物防治，具有开发为生防制剂的潜力。

Screening and evaluation of antagonistic bacteria as biocontrol agents against fungal pathogen Gaeumannomyces tritici

To screen antagonistic bacteria against wheat take-all caused by fungal pathogen Gaeumannomyces tritici, bacteria were isolated and screened from the rhizosphere soil of healthy wheat, and their antagonistic activity against G. tritici were evaluated by dual culture and pot experiment, respectively. The strains were identified according to morphology, physiological characteristics, and phylogenetic analysis. The results showed that two strains XJ-3 and XJ-4 screened from wheat rhizosphere, could obviously inhibit the mycelial growth of G. tritici with growth inhibition rate of 64.31% and 65.25%, respectively. According to morphology, physiological characteristics, and phylogenetic analysis based on gyrB sequences, XJ-3 and XJ-4 were identified as Bacillus velezensis. The antifungal substances in fermentations of XJ-3 and XJ-4 were heat stability and non-proteinaceous secondary metabolites. Strains XJ-3 and XJ-4 could promote the growth of wheat seedlings, with the length of seedlings significantly increased by 6.48% and 13.12%, respectively, and the dry weight of seedling increased by 1.30% and 14.29%, of which XJ-4 was much better. Pot experiment showed that strains XJ-3 and XJ-4 could suppress the infection of G. tritici with control efficacy of 51.29% and 52.46%, respectively. These results indicated that strains XJ-3 and XJ-4 were promising biological control agents for wheat take-all disease.