Adsorptive Behavior of Ethanedinitrile in Stored Grain Systems and Its Metabolic Impacts on Wheat and Insects

Yujia Zhang

As ethanedinitrile (EDN) is a novel fumigant for the protection of stored wheat, this study investigates the viability of EDN through a multi-faceted approach, examining its interaction with the grain matrix, impact on grain quality, and efficacy against phosphine-resistant insect populations. The first part of the study quantifies the fundamental sorption dynamics of EDN in wheat systems. Sorption, which reduces fumigant concentration, was found to be strongly influenced by both commodity characteristics and environmental conditions. Wheat germ, with its high lipid and protein content, exhibited the greatest sorption capacity, while milled fractions like bran showed the fastest sorption rates due to their large surface area. Crucially, sorption increased significantly with rising temperature and moisture content, and a positive correlation indicating that an activated process, likely chemisorption, is the dominant mechanism rather than physical adsorption. These findings provide a predictive foundation for optimizing application parameters, such as filling ratio and initial dosage, to minimize fumigant loss and maximize fumigation efficacy. Subsequently, the study investigated the previously uncharacterized phytotoxic effects of EDN on wheat. Fumigation at an insecticidally effective dose (5 mg/L) was found to be physiologically damaging, significantly impairing seed germination, vigor, and subsequent seedling growth. Key metabolic perturbations included a shift in terpenoid biosynthesis toward defense-related compounds, providing the first mechanistic link between EDN exposure and physiological damage in wheat. The final phase of the study elucidated EDN’s toxicological mode of action and assessed the potential for the development of cross resistance between EDN and phosphine in phosphine-susceptible and -resistant strains of Tribolium castaneum and Rhyzopertha dominica. A comparative metabolomic approach revealed that EDN exerts a dual toxicological mechanism: it induces systemic metabolic disruption by interfering with energy metabolism, while simultaneously inflicting severe, direct damage to the insect cuticle, compromising its physical integrity. Although phosphine-resistant strains mounted a heightened systemic defense response, indicating partial metabolic cross-resistance, this was insufficient to confer protection. The key finding is that EDN’s damaging effect on the cuticle is a distinct mechanism from the metabolic pathways that confer phosphine resistance. This ability to circumvent existing resistance mechanisms by attacking a primary physical barrier ensures its high efficacy against resistant populations. In conclusion, this thesis provides a holistic understanding of EDN’s behavior and impacts within a stored grain ecosystem. It establishes a quantitative basis for managing its high adsorptivity, clarifies the phytotoxic risks to grain quality, and validates a dual mode of action that overcomes phosphine resistance. These integrated findings are essential for developing safe, effective, and sustainable fumigation and resistance management strategies, positioning EDN as a critical tool for the future of stored-product protection.

Adsorptive Behavior of Ethanedinitrile in Stored Grain Systems and Its Metabolic Impacts on Wheat and Insects

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