Hydrophobic nano-calcium superphosphate enhances leaf disease resistance via coordinated physical, biochemical, and phyllosphere responses.

Hydrophobic nano-calcium superphosphate (NPS1) is a novel nano-fertilizer that has shown great potential for enhancing plant growth and suppressing foliar diseases. However, the mechanisms underlying these effects remain unclear. We investigated the responses of grape leaves and phyllosphere microbiota to NPS1 under both open-field and rain-shelter cultivation systems. NPS1 application significantly reduced leaf wetness duration and the disease severity of downy and powdery mildew, increased leaf-associated phosphorus retention, which remained elevated at later sampling stages, while enhancing vine growth, increasing SOD and POD activities, and inhibits several grape pathogens in vitro. Integrated transcriptomic and metabolomic analyses identified substantial changes in gene expression and metabolite accumulation following NPS1 treatment, characterized by the upregulation of stress-responsive genes (WRKY41, PEROXIDASE, and EREBP) and enrichment of pathways related to phenylpropanoid and secondary metabolite biosynthesis. Exogenous validation experiments indicated that coumaric acid and lignin were associated with enhanced seedling growth and restricted pathogen growth in vitro. Furthermore, amplicon sequencing revealed significant shifts in the composition, diversity, and co-occurrence patterns of phyllosphere microbial communities, accompanied by reduced relative abundances of pathogen-associated taxa (e.g., Erysiphe and oomycetes). Notably, representative beneficial isolates (e.g., Sphingomonas spp. and Bacillus spp.) exhibited stronger pathogen inhibition when combined with NPS1 than when applied alone. Collectively, these findings indicate that NPS1 alters the leaf surface conditions through reduced leaf wetness, associated with coordinated changes in plant physiological responses, metabolite accumulation, and phyllosphere microbial communities, which may be linked to reduced disease severity and improved grapevine performance.