Mycovirus-mediated plant vaccine enhances rice growth and disease resistance via seed biopriming

Conventional agricultural practices heavily rely on chemical inputs, posing risks to environmental and food safety. Seed biopriming with beneficial microorganisms offers a sustainable alternative to improve crop performance and resilience. Previously, we showed that the mycovirus-mediated hypovirulent strain DT-8 of Sclerotinia sclerotiorum functioned as a plant vaccine that significantly increased wheat and rapeseed yield. In this study, we utilized a laboratory-formulated plant vaccine based on strain DT-8 as a seed biopriming agent for rice. Through systematic optimization of seed priming parameters with plant vaccine, we defined that treatment at 24°C for 12 hours with a 3-day fermented broth (50 mL kg -1 seed; mycelial fresh weight: 50 g L -1 ) achieved more than 80% colonization efficiency without compromising germination. Microscopy confirmed root colonization by the plant vaccine, showing both intercellular and intracellular hyphal growth along the root axis without appressorium formation. Under both greenhouse and field conditions, plant vaccine-primed rice plants exhibited substantially enhanced growth traits, including plant height, chlorophyll content, dry weight, tiller number and yield. Furthermore, plant vaccine priming markedly reduced the incidence of rice false smut caused by Ustilaginoidea virens , under both artificial inoculation and natural field conditions. Transcriptome analysis further revealed the upregulation of growth-related genes. Concurrently, a significant enrichment of defense response terms and the diterpenoid biosynthesis pathway was observed, indicating the activation of key antimicrobial defenses. Our finding demonstrated that mycovirus-mediated plant vaccine serves as an effective seed priming agent, promoting rice growth and triggering systemic resistance.