香樟黑斑病病原菌鉴定及其拮抗菌B505的生防效果

为明确引起香樟黑斑病的病原菌，发掘防治该病害的生防细菌资源，根据科赫法则，采用组织分离法对引起香樟黑斑病的病原菌进行分离纯化。依据形态特征及ITS、 Alta1、gdp基因对病原菌进行分类鉴定；测定不同培养基、温度、pH等因素对病原菌生长的影响；采用平板对峙法筛选香樟黑斑病拮抗细菌，并对其进行抑菌活性试验。结果表明，引起香樟黑斑病的病原菌为互隔交链孢菌Alternaria alternata，其最佳生长温度为25 ℃，最适pH为6.5，最适培养基为PDA培养基。筛选获得1株对香樟黑斑病有较强抑制作用的菌株B505，鉴定为贝莱斯芽胞杆菌Bacillus velezensis，该菌株可强烈抑制香樟黑斑病病原菌的菌丝生长和孢子萌发，对香樟离体叶片黑斑病的抑制率为55.6%，以上结果为生物防治香樟叶部病害提供了新的思路。

Isolation and Identification of Pathogen Causing Camphor Black Spot Disease and Biocontrol Characteristics of Antagonistic Bacillus velezensis B505

This study aimed to identify the pathogen causing the black spot disease on Cinnamomum camphora and to investigate the potential biocontrol bacteria resources for the preventation and control of this disease.The pathogen was isolated and purified using the tissue isolation method.The pathogen was identified through the integration of colony,micromorphology,and ribosomal rDNA-ITS testing.This study also explored effects of physical and chemical factors,such as the medium,temperature,and pH on its growth.Bacteria with antagonistic properties against camphor black spots were screened using the plate confrontation method,and their antibacterial activity was tested.The results showed that the pathogen causing camphor black spots was Alternaria alternata.The optimum growth temperature,pH,and medium were 25 ℃,6.5,and potato dextrose agar,respectively.The Bacillus velezensis strain B505 was screened for its strong inhibitory effects on camphor black spots, achieved by suppressing both pathogen mycelial growth and spore germination.In vitro testing revealed a leaf black spot inhibition rate of 55.6% on Cinnamomum camphora,the above results provide a novel approach to the biological control of camphor leaf diseases.