Biocontrol potential of lipopeptides produced by the novel Bacillus altitudinis strain TM22A against postharvest Alternaria rot of tomato

Bacillus genus exhibits antagonistic potential against a broad range of pathogenic fungi. This study presents the antifungal potential of lipopeptides (LPs) produced by a novel strain Bacillus altitudinis TM22A to suppress the infection of Alternaria rot on tomato. We investigated the antifungal effect of ten Bacillus species against Alternaria alternata, where four Bacillus strains TM22A, MCM61, S2, and CPCF54 exhibited antifungal activity. The LPs extracted from TM22A, MCM61, S2, and CPCF54 restricted mycelial growth and conidial germination of A. alternata in vitro with the highest inhibition produced by TM22A. Liquid chromatography and mass spectrometry (LC-MS) analysis revealed the presence of surfactin, fengycin, iturin, bacillibactin, and bacilysin in strain TM22A at 1036.69, 1435.76, 1085.58, 883.26, and 271.13 m/z respectively. In an In planta assay LPs from TM22A caused the lowest lesion diameter and disease incidence on tomato fruit. Furthermore, the activity of defense enzymes viz, catalase (CAT), polyphenol oxidase (PPO), peroxidase (POD), superoxide dismutase (SOD), and phenylalanine ammonia-lyase (PAL) was enhanced in Bacillus LPs treated tomato fruit with the more pronounced impact by TM22A. Postharvest quality analysis revealed little impact on ascorbic acid, fruit pH, total soluble solids (TSS), titratable acidity (TA), weight loss, and fruit firmness compared to healthy control. This is the first comprehensive study to reveal the antifungal effect of Bacillus-derived LPs against postharvest Alternaria rot of tomato and its role in defense elicitation to protect the fruit from pathogen invasion.