biostudies-literatureQin Qsupported by Pests and Diseases Green Prevention and Control Major Special Project446https://www.ebi.ac.uk/biostudies/studies/S-EPMC12194751biostudies-literatureUnknown11(6)The fungus <i>Alternaria alternata</i>, which causes tobacco brown spot disease, poses a serious threat to the tobacco industry. Beneficial microorganisms and their secondary metabolites have emerged as a promising green strategy for disease management. This study recovered 16 endophytic bacterial strains from <i>Mentha haplocalyx</i> Briq., a therapeutic herb. The study revealed that strain B5, with an inhibition rate of 82.76%, exhibited the highest antifungal activity against <i>A. alternata</i>. This strain exhibited broad-spectrum antifungal activity, with inhibition rates ranging from 66.34% to 87.23%. Phylogenetic analysis of 16S rDNA and <i>gyrA</i> gene sequences identified it as <i>Bacillus velezensis</i> (GenBank: PV168970 and PV173738). Further characterization revealed that stJournal of fungi (Basel, Switzerland)Isolation and Identification of Endophytic Bacterium B5 from <i>Mentha haplocalyx</i> Briq. and Its Biocontrol Mechanisms Against <i>Alternaria alternata</i>-Induced Tobacco Brown Spot.PMC12194751110202201023 ( LS-07 )Qin QMa BLiu BWei XZhou YSun ZfalseIsolation and Identification of Endophytic Bacterium B5 from <i>Mentha haplocalyx</i> Briq. and Its Biocontrol Mechanisms Against <i>Alternaria alternata</i>-Induced Tobacco Brown Spot.The fungus <i>Alternaria alternata</i>, which causes tobacco brown spot disease, poses a serious threat to the tobacco industry. Beneficial microorganisms and their secondary metabolites have emerged as a promising green strategy for disease management. This study recovered 16 endophytic bacterial strains from <i>Mentha haplocalyx</i> Briq., a therapeutic herb. The study revealed that strain B5, with an inhibition rate of 82.76%, exhibited the highest antifungal activity against <i>A. alternata</i>. This strain exhibited broad-spectrum antifungal activity, with inhibition rates ranging from 66.34% to 87.23%. Phylogenetic analysis of 16S rDNA and <i>gyrA</i> gene sequences identified it as <i>Bacillus velezensis</i> (GenBank: PV168970 and PV173738). Further characterization revealed that st2025-01-01T00:00:00Z2025 Jun2026-04-08T19:37:41.01Z2026-04-08T13:56:07.484ZS-EPMC121947514055895810.3390/jof11060446