Nanoscale sulfur has attracted increased interest as a multi-functional sustainable agricultural amendment to manage plant pathogens, improve crop productivity, enhance nutrition, and prevent heavy metal accumulation. Here, pristine (nS) and surface coated (cS) sulfur nanoparticles were foliar applied or added to soil that was planted with tomato and infested with Fusarium under greenhouse and field conditions. Bulk sulfur (bS), ionic sulfate (iS), and healthy controls treated with the same sulfur containing compounds were included to enable mechanistic understanding. The measured endpoints included time dependent agronomic and photosynthetic parameters, disease severity, yield, and a range of mechanistic biochemical and molecular endpoints, including the expression of 13 genes related to two S bioassimilation pathways and pathogenesis-response, and tissue-specific metabolomic profiles. The impact of treatment on the rhizosphere bacterial microbiome was also evaluated. Disease reduced biomass by up to 87%, but amendment with nS and cS significantly reduced disease progress by 54-56% compared to the infested controls. Increased S accumulation was evident in plant roots and leaves, independent of S type. Molecular analysis revealed particle size and coating specific impacts on the plants. For nS and cS, two-photon microscopy and time dependent gene expression data revealed a nanoscale specific elemental S bioassimilation pathway within the plant tissues. These findings correlated well with a detailed metabolomic profiling of plant tissues at 4, 8, and 16 d which exhibited increased disease resistance and plant immunity related metabolites with nanoscale treatment. The data also demonstrate a time-sensitive physiological window whereby nanoscale stimulation of plant immunity will be effective. An analysis of the rhizosphere soil bacterial community revealed minimal impacts from S treatment. A parallel field study showed that nanoscale sulfur increased the early yield per plant by 54% under diseased conditions, demonstrating that a $33 investment per acre for a form of a required nutrient (cS) led to an increase of $12,200 in economic return per acre in the complete absence of conventional pesticides. These findings provide significant mechanistic insight into novel nanomaterial-based suppression of plant disease, and significantly advances efforts develop sustainable of nano-enabled agricultural strategies for crop protection.

Nanoscale sulfur uniquely suppresses fungal disease and increases biomass and yield of crop plants

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ACS Fall 2022

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