Novel Barley Bacterial Endophytes as Potential Antagonists for Managing Fusarium Head Blight and Other Fusarium ‐Induced Diseases

Fusarium head blight (FHB) is a devastating disease of barley and other small‐grain cereals across many regions of the world. Current disease management strategies, including the use of genetic resistance, fungicides and crop rotation, only provide partial control of FHB. As an environmentally friendly alternative, biological control attracts attention from researchers, growers and consumers. The plant microbiome, especially endophytic bacteria, has emerged as a promising source of biological control agents against FHB. Endophytes are generally nonpathogenic microorganisms that inhabit plant tissues without causing visible symptoms of infection or disease. In this study, bacterial endophytes were isolated from grains, stems and roots of FHB‐infected and non‐FHB‐infected (control) barley plant samples in 2022. The samples represented cultivated and wild genotypes at three growth stages—booting (S1), mid‐dough (S2) and physiological maturity (S3). A total of 12 isolated antagonistic bacterial endophytes were evaluated for their ability to inhibit the in vitro mycelial growth of seven Fusarium isolates representing six species: Fusarium avenaceum , F. culmorum , F. graminearum (3‐acetyldeoxynivalenol [3ADON] and 15‐acetyldeoxynivalenol [15ADON] chemotypes), F. oxysporum , F. poae and F. pseudograminearum , using dual culture assays. Bacillus mycoides NA_145.1 showed the highest mean inhibition of mycelial growth across all Fusarium species tested (75.9%). Among the bacterial antagonists, Serratia and Bacillus species were predominant. Whole‐genome sequencing and phylogenetic analyses revealed three isolates that may represent novel bacterial species. This study identified several novel bacterial endophytes in barley exhibiting antagonism towards Fusarium species that cause FHB in barley and other small‐grain cereals.