Insights into biological and molecular underpinnings of how post-plant nematicides suppress Meloidoygne incognita
Catherine Wram: Oregon State University
<div><em>Meloidogyne</em> species, root-knot nematodes, are one of the most important groups of plant-parasitic nematodes globally due to their ability to infect and damage almost all cultivated plants. Although widespread and economically important, there are few control measures to combat these pests. Recently several new nematicides have been discovered that can be used to manage nematodes post-plant. To gain a deeper understanding of the mechanisms of these new chemistries and use this understanding to maximize efficacy and minimize the development of resistance, we characterized gene expression in <em>Meloidogyne incognita</em> treated with sub-lethal doses of common four post-plant nematicides. Second-stage juveniles (J2) were exposed to a 24-hour sub-lethal dose of four post-plant nematicides, which resulted in 50% mortality (LD<sub>50</sub>), after which RNA was extracted and gene expression determined using RNAseq. Post-plant nematicides used in this study were oxamyl, fluopyram, fluensulfone, and fluazaindolizine, which represent new and old nematicides, encompass various modes of action, and represent a range of LD<sub>50</sub> concentrations. Twenty-four hour LD<sub>50</sub> concentrations for oxamyl, fluopyram, fluensulfone, and fluazaindolizine were 100 ppm, 1 ppm, 95 ppm, and 230 ppm, respectively. In water replacement experiments and mobility assays, exposure to sublethal doses of fluazaindolizine and fluensulfone resulted in death of <em>M. incognita</em>, while the nematode recovered from sublethal doses of oxamyl and fluopyram. Over 2,500 genes were significantly differentially expressed in <em>Meloidogyne incognita</em> J2 exposed to LD<sub>50</sub> concentrations, with a 16-fold increase in expression of iron binding proteins and oxioreductases</div>
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