Garlic Polysulfides: The science behind the sulfurs & their application in crop protection against plant pathogenic nematodes

Eposi Enjema, Carine (2025) Garlic Polysulfides: The science behind the sulfurs & their application in crop protection against plant pathogenic nematodes. Doctoral thesis, University of East Anglia.

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Abstract

Plant-pathogenic nematodes (PPNs) impose major constraints on global food production, and their management is becoming increasingly difficult due to regulatory restrictions on conventional chemical nematicides and the implications of climate change on their ecology. The development of novel nematicides offering both efficacy and environmental sustainability has thus become a focus of recent research.

In this study, to harness the chemistry of garlic-derived diallyl polysulfides (DAS) as sustainable alternatives, the nematicidal efficacy of the DAS-based formulation Nemguard SC (CLAIL0021) and Velum Prime (fluopyram) were investigated individually and in combination, using in vitro bioassays on Caenorhabditis spp. and Steinernema feltiae as well as in two field experiments targeting potato cyst nematodes (PCN) in Hilborough, Norfolk, UK. A positive interaction between CLAIL0021 and fluopyram was observed for the first time, resulting in enhanced nematicidal activity against C. elegans, improved yield in the profitable size grade of Maris Peer salad potato crop, and reduced PCN multiplication (Pf/Pi), supporting their potential co-use within integrated pest management (IPM) systems. Mechanistic studies using the Amplex Red assay, H2DCF-DA, and the redox-sensitive mutant strains (VC433; sod-3(gk235) X, and TK22; mev-1(kn1) III) demonstrated that DAS may exert their nematicidal effects at least in part via the induction of oxidative stress which disrupts cellular redox homeostasis leading to compromised nematode viability. A rigorous evolutionary selection experiment applying selective pressure over twenty generations on C. remanei populations revealed no significant development of resistance or cross-resistance to CLAIL0021 or fluopyram, although fecundity was further perturbed especially under the combined treatment. The broader implications of this study contribute to a deeper understanding of DAS chemistry and indicate that DAS-based formulations may constitute equally effective alternatives to chemical nematicides at a much lower expense to environmental and human health.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Pharmacy (former - to 2024)
Depositing User:	Chris White
Date Deposited:	10 Feb 2026 10:57
Last Modified:	10 Feb 2026 10:57
URI:	https://ueaeprints.uea.ac.uk/id/eprint/101886
DOI:

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