Pseudomonas from Potato Inhibited the Pathogenicity of Verticillium nonalfalfae through the BCAA Biosynthesis Pathway

Verticillium wilt severely impacts potato production, necessitating eco-friendly control strategies. This study used 16S sequencing to analyze bacterial communities in potatoes and fungi before and after inoculation with Vn011, the Verticillium wilt pathogen. Inoculation increased Pseudomonas abundance in potato stems from 0.26% to 1.64%. Importantly, Pseudomonas was absent in the long term laboratory-maintained fungal strain Vn011 but represented 90.95% of the bacterial community in the freshly isolated fungal strain Vn011^potato from potato plants. Therefore, a Pseudomonas simiae strain, Ps4, isolated from Vn011^potato, was found to inhibit Verticillium nonalfalfae, promote potato growth, and reduce the disease index from 0.9 to 0.09 in coinoculation assays. Transcriptome analysis suggested that Ps4 suppresses Vn011 by targeting its branched-chain amino acid (BCAA) biosynthesis pathway, with growth inhibition reversed by BCAA supplementation. This study reveals P. simiae as a promising biocontrol agent against potato Verticillium wilt and highlights the BCAA pathway as a novel target for disease management.