Paenibacillus polymyxa K17 Controls Leaf Spot of Tea Plant by Impairing Fungal Cellular Structure and Energy Metabolism

Utilizing biocontrol microbes has emerged as a promising
strategy
for sustainable disease management in tea cultivation. Here, a novel
strain Paenibacillus polymyxa K17 was
isolated, which possesses broad-spectrum antifungal capacity against
14 phytopathogens from multiple crops, with inhibition rates of 53–82%.
Notably, P. polymyxa K17 demonstrated
comparable or occasionally superior control efficacy to the fungicide
kasugamycin in leaf spot disease caused by Lasiodiplodia
gonubiensis across three tea cultivars. P. polymyxa K17 induced mycelial deformation and
cellular damage of L. gonubiensis.
Meanwhile, strain K17 metabolites markedly suppressed the gene expression
in multiple pathways related to fungal energy metabolism, including
oxidative phosphorylation, TCA cycle, and pyruvate metabolism. Correspondingly,
the activities of the mitochondrial complex and the levels of ATP
and pyruvate in L. gonubiensis were
markedly decreased. These findings indicate that P.
polymyxa K17 inhibits fungal growth by disrupting
energy metabolism and cellular structure, highlighting its potential
for controlling multiple fungal diseases in tea gardens.