Kentucky bluegrass powdery mildew, caused by the fungus Blumeria graminis f. sp. poae, is a destructive disease affecting Poa pratensis L. In this study, endophytic bacteria were isolated from the resistant Kentucky bluegrass cultivar ‘Taihang’. Employing a combination of conidia germination inhibition assays and control efficacy tests, the biocontrol endophytic bacterial strains were screened. The impact of inoculation with the powdery mildew pathogen and biocontrol endophytic bacteria on the difference in endophytic bacterial community in the leaves of Kentucky bluegrass were studied via Illumina Miseq high-throughput 16S ribosomal RNA gene sequencing technology. A total of 18 endophytic bacterial isolates were obtained from ‘Taihang’, belonging to 3 phyla: Proteobacteria (3 isolates), Actinobacteria (6 isolates), and Firmicutes (9 isolates). The conidia germination assay revealed that isolates 6213 (Bacillus sp.) and 718 (Neobacillus sp.) exhibited the strongest inhibitory against Blumeria graminis f. sp. poae, with inhibition rate exceeding 80%. Isolate 718 exhibited superior control efficacy over strain 6213. A concentration of 10⁹ colony-forming units per milliliter (CFU/mL) was the most effective in suppressing powdery mildew on Kentucky bluegrass. The abundance of Proteobacteria on Kentucky bluegrass after the application of isolate 718 may enhance the resistance of Kentucky bluegrass to powdery mildew, and the dominant endophytic bacterial communities were Burkholderiales, Burkholderiaceae and Cupriavidus, indicating that the application of isolate 718 modulated the plant’s response to powdery mildew infection. These results demonstrate that isolate 718 enhanced the resistance of Kentucky bluegrass against powdery mildew by reshaping the endophytic bacterial community within the leaves. These findings provide molecular insights into plant−pathogen−endophytic bacteria interactions and support the development of sustainable strategies, eco-friendly strategies for plant diseases management.

Alfalfa (Medicago sativa L.) is a globally important perennial forage crop, but molecular breeding is constrained by slow, genotype-dependent regeneration