香梨黑斑病病原菌分离及拮抗菌筛选鉴定

【目的】从香梨树体中筛选出对香梨采后黑斑病病原菌具有拮抗作用的内生菌,为香梨采后生物保鲜奠定基础。【方法】采用组织分离法,对香梨采后黑斑病病原菌及梨树内生菌进行分离,采用ITS基因与16S rRNA基因引物分别对分离出的病原菌和拮抗菌进行测序,采用平板对峙法测定内生菌的拮抗效果,并对拮抗效果优良的拮抗菌采用离体果实进行防效测定。【结果】分离得到香梨采后黑斑病病害病原菌1株,鉴定为Alternatia alternata XL₂。从梨树叶片及枝条中分离出内生菌16株,其中8株对Alternatia alternata XL₂有抑制作用,8株拮抗菌均为芽孢杆菌属,分别为Bacillus velezensis 5株、Bacillus paralicheniformis 、Bacillus siamensis 和Bacillus tequilensis 各1株,牛津杯琼脂扩散实验中Bacillus velezensis NY₂、NY₇抑菌效果最佳,其次为NY₁₅,抑菌圈直径均可达20 mm以上。离体果实抑菌实验中短期效果最佳的为NY₂,使用第4 d时抑菌率可达80%以上,中长期效果较佳的为NY₁₁,使用第7 d天时仍可达20%以上。【结论】筛选获得2株优良的香梨采后黑斑病拮抗菌。

Isolation of Pathogenic Bacteria and Screening and Identification of Antagonistic Bacteria of Black Spot of Fragrant pear

【Objective】 The purpose of this study is to screen the endophytic bacteria with antibacterial effect from the Korla pear tree with a view to using the endophytic biocontrol agent to keep the pear fresh after harvesting.【Method】 The pathogen of postharvest black spot of fragrant pear and endophytic bacteria were isolated by tissue separation method and then the isolated strains were sequenced by ITS gene and 16S rRNA gene.Also, the plate confrontation method was used to screen the antagonistic bacteria against Alternatia alternata XL₂ from the screened endophytic bacteria, and bacteriostasis experiments of the antagonistic bacteria were conducted in vitro fruits.【Result】 The pathogen of postharvest diseases of Korla pear Alternatia alternata XL₂ was obtained in this experiment, and 16 strains of endophytic bacteria were isolated from the leaves and branches of pear trees, among which 8 strains had inhibitory effect on Alternatia alternata XL₂.They were 1 Bacillus paralicheniformis, 5 Bacillus velezensis, 1 Bacillus siamensis and 1 Bacillus tequilensis.Among them, Bacillus velezensis NY₂, NY₇ and NY₅ had the best antibacterial effect in the Oxford cup experiment, and the diameter of antibacterial zone was more than 20 mm.In the bacteriostatic experiment of Korla pear, NY₂ and NY₁₅ had the best bacteriostatic effect, and the bacteriostatic rate was more than 30%.In the bacteriostatic test in vitro fruits, the bacteriostatic rate of NY₂ reached more than 80% in the fourth day after inoculation, and the bacteriostatic effect of NY₁₁ was more stable than others.【Conclusion】 In this experiment, 2 strains of endophytic bacteria with antibacterial effect are screened.