Dual-Action Biocontrol Agent: Bacillus velezensis Lipopeptides Mitigate Potato Dry Rot by Disrupting Fusarium solani and Priming Host Defense

Potato dry rot, induced by pathogenic Fusarium species, is a prevalent postharvest fungal disease that leads to significant economic losses. This research illustrates the biocontrol efficacy of Bacillus velezensis strain 2-1-9-CJK-2 against potato dry rot. The strain successfully inhibited disease progression, diminished oxidative damage in potato tubers, and augmented the activity of essential defense-related enzymes. It effectively colonized potato tubers and sustained consistent inhibitory activity under diverse environmental challenges. And its cell-free supernatant (CFS) retained consistent inhibitory activity. The crude lipopeptides (CLs) produced by this strain induced hyphal deformation, fragmentation, and cytoplasmic leakage in Fusarium solani. Transmission electron microscopy (TEM) further revealed that CL treatments triggered organelle degradation in the pathogen, with mitochondrial disintegration being particularly prominent. Transcriptomic analysis indicated that CLs upregulated genes linked to mitochondrial autophagy in the pathogen and stimulated plant defense mechanisms, notably the MAPK signaling cascade, in potatoes. The findings were additionally corroborated by qRT-PCR. B. velezensis strain 2-1-9-CJK-2 is a promising biocontrol agent and a great resource for the development of antifungal formulations to enhance sustainable potato production.