Alkaline-responsive, zein-based nanospheres with enhanced vertical soil mobility for sustained and targeted control of soybean root rot

Soybean root rot, primarily caused by Fusarium and Phytophthora spp., severely damages root tissues, impairs nutrient uptake, and leads to plant death, particularly in saline-alkaline soils, where high pH, salt stress, and deteriorated soil conditions reduce the stress resistance of soybean plants. Conventional chemical treatments are less effective owing to the poor vertical mobility of fungicides in alkaline soils. Stimuli-responsive controlled-release formulations can improve the bioavailability of active ingredients, reduce application frequency, and minimize environmental impact. Here, we present a sustainable, biodegradable, and environmentally benign delivery system based on zein, a plant-derived protein. Zein was modified with non-toxic succinic anhydride to improve water dispersibility, resulting in a green carrier (SZ) with reduced ecological risk. The UV-sensitive fungicide difenoconazole (Di) was encapsulated into this carrier via nanoprecipitation to construct a stimuli-responsive nano-enabled delivery system (Di@SZ). Di@SZ exhibited alkaline-triggered release, with rapid release in alkaline conditions. Compared to the commercial emulsifiable concentrate (EW), Di@SZ nanoparticles showed a 3.03-fold improvement in UV resistance. They enhanced vertical mobility of Di in soil, enabling targeted root delivery during drip irrigation in saline-alkaline soils. Pot experiments demonstrated that Di@SZ provided stronger and longer-lasting protection against soybean root rot than EW. Moreover, the system exhibited superior biosafety, with 2.77-fold lower toxicity to soil earthworms relative to EW. These findings underscore Di@SZ as a sustainable, materials-based plant protection technology that integrates renewable resources, reduces environmental impact, and enhances efficacy, offering a promising approach for eco-friendly disease management in agriculture.