Hydrolytic Enzymes and Siderophore-mediated Biocontrol of Wheat Foliar Blight Pathogens by Bacillus spp.

Fungal pathogens represent a significant threat to global crop plants, necessitating the development of effective biocontrol agents to mitigate associated risks. Rhizobacteria, known for their diverse benefits, are crucial for promoting plant growth, inhibiting pathogens, and enhancing soil health. The present study demonstrated the ability to reduce the mycelial growth of Bipolaris sorokiniana and Alternaria triticina infection, suggesting as a biocontrol agent for agricultural applications. In this context, four strains of Bacillus spp. isolated from wheat rhizosphere soil exhibited promising antagonistic effects against foliar blight pathogens Bipolaris sorokiniana and Alternaria triticina. Notably, strains P10 and UP11 demonstrated the most potent inhibition of mycelial growth in dual culture assays. Microscopic examination revealed that diffusible compounds induced morphological abnormalities in fungal structures. Further investigations into the biocontrol mechanisms of these strains revealed the production of hydrolytic enzymes, and antimicrobial metabolites. P10 and UP11 showed the highest percent of mycelial weight reduction (%MWR) against Bipolaris sorokiniana (72.43%, 66.10%) and Alternaria triticina (77.40%, 74.29%). Moreover, the antagonistic activity exhibited variation influenced by factors such as pH, and temperature, with maximal inhibition observed during the early stationary phase. The research found a direct relationship between the inhibition of fungal pathogens' growth and the levels of certain hydrolytic enzymes such as chitinase, β-1,3-glucanase, and protease as well as antimicrobial metabolites like siderophore present in the antagonist treatment's culture medium. Conversely, levels of cellulase, polygalacturonase and xylanase were comparatively low in these treatments. They showed negative correlation with % mycelial growth reduction. Overall, these findings highlight the potential of selected antagonistic strains, particularly P10 and its consortium with UP11, as effective biocontrol agents against foliar blight diseases, offering promising prospects for sustainable agricultural practices.