Nitrate‐constructed fungal communities and rhizosphere metabolites confer resistance to Fusarium wilt in cucumber

Nitrogen fertilization regimes are a critical determinant of soilborne disease outcomes in intensive agriculture, yet the mechanisms through which different nitrogen forms exert their influence remain poorly understood. Our study investigates how nitrate and ammonium nutrition differentially modulate the severity of Fusarium wilt in cucumber by altering the rhizosphere microbiome and metabolome. We utilized a split-root system to study the effects of nitrate and ammonium on disease progression, integrating ITS amplicon sequencing and gas chromatography mass spectrometry metabolomics. Nitrate nutrition promoted the recruitment of beneficial fungal taxa and the accumulation of antifungal metabolites, which collectively suppressed pathogen growth and enhanced plant health. By contrast, ammonium supply created a rhizosphere environment conducive to pathogen growth by selectively enriching pathogenic fungi and driving metabolic reprogramming, which ultimately heightened plant susceptibility. Split-root experiments revealed that local nitrate application stimulated resveratrol accumulation and enriched Funneliformis in the rhizosphere. In vitro inhibition assays showed that resveratrol directly suppressed Fusarium mycelial growth, and pot experiments demonstrated that exogenous resveratrol application and inoculation with Funneliformis both enhanced plant performance. Our findings reveal how nitrogen forms regulate plant-microbe-metabolite interactions to determine soilborne disease outcomes, providing a foundation for nutrition-based management strategies that can reduce fungicide reliance through natural suppression.