Antagonistic potential and biological control mechanisms of Pseudomonas strains against banded leaf and sheath blight disease of maize.

Rhizoctonia solani, the causal agent of banded leaf and sheath blight (BL&SB), poses a significant threat to maize and various crops globally. The increasing concerns surrounding the environmental and health impacts of chemical fungicides have encouraged intensified concern in the development of biological control agents (BCAs) as eco-friendly alternatives. In this study, we explored the potential of 22 rhizobacteria strains (AS1-AS22) isolates, recovered from the grasslands of the Pithoragarh region in the Central Himalayas, as effective BCAs against BL&SB disease. Among these strains, two Pseudomonas isolates, AS19 and AS21, exhibited pronounced inhibition of fungal mycelium growth in vitro, with respective inhibition rates of 57.04% and 54.15% in cell cultures and 66.56% and 65.60% in cell-free culture filtrates. Additionally, both strains demonstrated effective suppression of sclerotium growth. The strains AS19 and AS21 were identified as Pseudomonas sp. by 16S rDNA phylogeny and deposited under accession numbers NAIMCC-B-02303 and NAIMCC-B-02304, respectively. Further investigations revealed the mechanisms of action of AS19 and AS21, demonstrating their ability to induce systemic resistance (ISR) and exhibit broad-spectrum antifungal activity against Alternaria triticina, Bipolaris sorokiniana, Rhizoctonia maydis, and Fusarium oxysporum f. sp. lentis. Pot trials demonstrated significant reductions in BL&SB disease incidence (DI) following foliar applications of AS19 and AS21, with reductions ranging from 25 to 38.33% compared to control treatments. Scanning electron microscopy revealed substantial degradation of fungal mycelium by the strains, accompanied by the production of hydrolytic enzymes. These findings suggest the potential of Pseudomonas strains AS19 and AS21 as promising BCAs against BL&SB and other fungal pathogens. However, further field trials are warranted to validate their efficacy under natural conditions and elucidate the specific bacterial metabolites responsible for inducing systemic resistance. This study contributes to the advancement of sustainable disease management strategies and emphasizes the potential of Pseudomonas strains AS19 and AS21 in combating BL&SB and other fungal diseases affecting agricultural crops.

Withania somnifera seed oil exhibits antibiofilm properties against drug-resistant Candida auris clinical isolate through modulation in cell permeability.

AIM: Candida auris, fast evolving drug-resistant fungus, poses an imminent global health threat. Alternative drug-resistance nonevoking treatment options are necessary. This study explored the antifungal and antibiofilm efficacies of Withania somnifera seed oil extracted using super critical CO2 (WSSO) against clinically isolated Fluconazole-resistant C. auris and its putative mode-of-action. METHODS AND RESULTS: Effects of WSSO on C. auris were tested by broth microdilution method, with observed IC50 at 5.96 mg ml-1. Time-kill assay revealed that WSSO is fungistatic. Mechanistically, ergosterol binding and sorbitol protection assays showed that C. auris cell membrane and cell wall are the targets for WSSO. Lactophenol: Cotton-Blue: Trypan-Blue staining confirmed loss of intracellular contents by WSSO treatment. Candida auris biofilm formation was disrupted by WSSO (BIC50: 8.52 mg ml-1). Additionally, WSSO exhibited dose and time-dependent mature biofilm eradication property with 50% efficacies at 23.27, 19.28, 18.18, and 7.22 mg ml-1 over 24, 48, 72, and 96 h, respectively. Biofilm eradication by WSSO was further substantiated through scanning electron microscopy. Standard-of-Care Amphotericin B, at its break-point concentration, (2 µg ml-1) was found to be inefficient as an antibiofilm agent. CONCLUSIONS: WSSO is a potent antifungal agent effective against planktonic C. auris and its biofilm.