松球壳孢拮抗细菌ZG7的分离与鉴定OA

[Objective]Shoot blight caused by Sphaeropsis sapinea is one of the major diseases affecting Pinus sylvestris var.mongolica.This study aimed to isolate and screen superior endophytic antagonistic bacteria from the host to provide novel strategies and methodologies for the biological control of this disease.[Methods]Endophytic bacteria with antagonistic effects against S.sapinea were screened from different tissues of P.sylvestris var.mongolica using the dual culture technique.Poten-tial isolates were identified through morphological,physiological,and biochemical characterization,as well as molecular biolo-gy methods.The antagonistic mechanism against S.sapinea was observed via scanning electron microscopy(SEM).Addition-ally,the antimicrobial spectrum,optimal fermentation conditions,and potential plant growth-promoting effects on the host were determined.[Results]An endophytic bacterial strain,designated ZG7,was isolated from the stem tissue of P.sylvestris var.mongolica.This strain exhibited significant antagonistic activity against S.sapinea,with an inhibition rate of 83.57%.Strain ZG7 was identified as Bacillus amyloliquefaciens.SEM observations revealed that ZG7 induced severe morphological ab-normalities in S.sapinea hyphae,including swelling,distortion,breakage,shrinkage,and increased branching.The strain demonstrated broad-spectrum antagonistic activity against eight tested phytopathogens,with inhibition rates exceeding 53%,the highest being against Colletotrichum gloeosporioides(80.12%).Furthermore,strain ZG7 exhibited nitrogen-fixing capa-bility and produced indole-3-acetic acid(IAA).Optimal fermentation conditions were determined as:temperature 37℃,initial pH 6.0,1%(v/v)inoculum size,and 10%(v/v)medium volume(10 mL per 100 mL flask).[Conclusion]B.amyloliquefa-ciens ZG7 exhibited significant antagonism against S.sapinea,a broad antimicrobial spectrum,and potential growth-promot-ing capabilities.These findings provided a theoretical foundation for the integrated management of shoot blight in P.sylvestris var.mongolica.