Foliar coronatine synergizes with rhizosphere-inoculated Trichoderma viride to suppress root rot by reshaping...

Replant failure severely constrains the sustainable production of high-value crops such as Panax notoginseng and Lilium spp. (lily), with root rot being a major disease responsible for substantial losses in yield and quality. Here, we evaluated a dual-compartment strategy combining foliar application of the defense elicitor coronatine (COR) with root inoculation of Trichoderma viride T3, applied individually or in combination. Across two crop species (P. notoginseng and lily) and both resistant and susceptible lily cultivars, the combined COR + T3 treatment consistently promoted plant growth and suppressed root rot more effectively than either treatment alone. Notably, COR alone exhibited no direct antifungal activity against root-rot pathogens in vitro, supporting its role as a plant-mediated defense inducer rather than a direct fungicide. Rhizosphere microbiome profiling revealed that the combined treatment significantly enriched beneficial taxa, particularly Trichoderma and Arthrobacter. Two representative OTUs, T. viride T3 (OTU769) and Arthrobacter sp. A1 (OTU17686), were further implicated as key contributors: both isolates inhibited the growth of lily root-rot pathogens and showed plant growth-promoting potential. Collectively, these results suggest that foliar COR can synergize with rhizosphere T. viride to mitigate replant failure by selectively reshaping the rhizosphere microbial community, enriching beneficial microbes, enhancing plant growth, and reducing root rot incidence. Under our conditions, the most effective treatment was COR (800× dilution) combined with T. viride T3, providing a practical and eco-friendly approach for managing soil sickness in intensive production systems.