Antagonism of rhizosphere DTN19 against the pathogenic fungi causing corm rot in saffron ( L.) .

Introduction: Corm rot in saffron ( L.) significantly impacts yield and quality. Non-toxic fungi, particularly species, are valuable for biological control due to their production of diverse and biologically active secondary metabolites.

Methods: This study aimed to isolate an effective antagonistic fungus against the pathogenic fungi causing corm rot in saffron. Four pathogenic fungi (, , , and ) were isolated from diseased saffron bulbs in Chongming. Initial screening through dual culture with these pathogens re-screening from rhizosphere soil samples of based on its inhibitory effects through volatile, nonvolatile, and fermentation broth metabolites. The inhibitory effect of biocontrol fungi on pathogenic fungi in vitro was evaluated by morphological observation and molecular biology methods.

Results: Antagonistic fungi were identified as DTN19. was identified as the most severe pathogen. SEM (scanning electron microscope) and TEM (transmission electron microscope) observations revealed that DTN19 significantly inhibited the growth and development of mycelium, disrupting its physiological structure and spore formation. Additionally, DTN19 demonstrated nitrogen fixation and production of cellulase, IAA (Indole acetic acid), and siderophores. Whole-genome sequencing of strain DTN19 revealed genes encoding protease, cellulase, chitinase, β-glucosidase, siderophore, nitrogen cycle, and sulfate transporter-related proteins.

Discussion: DTN19 may inhibit the propagation of pathogenic fungi by destroying their cell walls or producing antibiotics. It can also produce IAA and iron carriers, which have the potential to promote plant growth. Overall, DTN19 showed the development prospect of biological agents.