Exploring Paenibacillus terrae B6a as a Sustainable Biocontrol Agent for Fusarium proliferatum

Enriquay Smith ¹ Augustine Innalegwu Daniel ¹ Chelsey Smith ¹ Stacey Fisher ¹ Mbukeni Nkomo ² Marshall Keyster ¹ Ashwil Klein ^1,3*

• ¹ University of the Western Cape, Bellville, South Africa
• ² University of KwaZulu-Natal, Durban, KwaZulu-Natal, South Africa
• ³ Faculty of Natural Sciences, University of the Western Cape, Bellville, South Africa

The reliance on chemical fungicides for crop protection has raised environmental and health concerns, prompting the need for sustainable and eco-friendly alternatives. Biological control, using antagonistic microorganisms like Paenibacillus terrae B6a, offers an eco-friendly approach to managing disease causing phytopathogens. The objective of the study was to assess the efficacy of P. terrae B6a as a biocontrol agent against Fusarium proliferatum PPRI 31301, focusing on its in vitro antagonistic activity, its impact on fungal morphology and enzymatic content, and its ability to mitigate pathogeninduced stress in maize plants. In vitro antagonistic activity of B6a against F. proliferatum was carried out using standard protocol. In planta assay was carried out by bio-priming of maize seeds with 1 x 10 6 CFU/mL of B6a and infected with F. proliferatum for 7 days. Biochemical, enzymatic and antioxidants activities of bio-primed maize roots under F. proliferatum infection was carried out using spectrophotometric methods. In vitro antagonistic assays using dual culture and intracellular crude metabolites inhibited 70.15 and 71.64 % respectively of F. proliferatum. Furthermore, B6a altered the morphology and mycelia structure of F. proliferatum under High resolution scanning electron microscopy (HR-SEM). This was supported by an increase (p<0.05) in the chitin contents (48.03 %) and a decrease (p<0.05) in the extracellular polysaccharide content (48.99 %) and endo-β-1,4glucanase activity (42.32 %). The infection of maize seeds with F. proliferatum resulted in a significant decrease (p<0.05) in root lengths (37 %). Relative to the control and the infected seeds, bio-priming with B6a shows a significant increase (p<0.05) in the root lengths (44.99 %), with a significant decrease (p<0.05) in reactive oxygen species (ROS)-induced oxidative damage. In conclusion, P. terrae B6a may be a good biocontrol candidate and may be formulated into a bio-fungicide to control F. proliferatum and other related phytopathogens in economically important crops.