A Herpetosiphon llansteffanensis Strain from Forest Soil Exhibits Biocontrol Activity Against Pear Fire Blight

Fire blight, a devastating bacterial disease caused by <i>Erwinia amylovora</i>, has posed significant challenges to apple and pear production for over a century. This study introduces a gliding filamentous bacterium, the strain NSD29, isolated from natural forest soil in Xinjiang, China, as a biological control agent for managing this disease. Comprehensive characterization based on morphological, physiological, biochemical, 16S rRNA gene, and whole-genome analyses identified the strain NSD29 as <i>Herpetosiphon llansteffanensis</i>. The train NSD29 demonstrated potent predatory activity against <i>E. amylovora</i> in vitro. Its biocontrol efficacy was subsequently evaluated on detached leaves, inflorescences, young fruit, and shoots of fragrant pear under controlled greenhouse conditions. Results indicated that applying <i>H</i>. <i>llansteffanensis</i> NSD29 significantly inhibited lesion expansion on pear leaves and young fruit, achieving protective efficacies of 75.2% and 72.0%, respectively. Furthermore, pre-treatment spraying with NSD29 effectively reduced the incidence of blossom blight, with a control efficacy of 61.2%. On detached pear shoots, the application of NSD29 fermentation broth suppressed lesion expansion, demonstrating substantial protective (86.8%) and curative (75.6%) efficacies. This research provides the first evidence for the potential of <i>Herpetosiphon</i> species in the biological control of plant diseases, highlighting <i>H. llansteffanensis</i> NSD29 as a promising candidate for developing strategies to combat fire blight.