Two-spotted spider mite Tetranychus urticae adaptations to soybean Glycine max plant defences

Abstract: Two-spotted spider mite (TSSM) Tetranychus urticae Koch (Acari: Tetranychidae)is a damaging arthropod pest of many crop plant species, in part due to TSSM’s ability to adaptto crop plant defenses including secondary metabolites. TSSM can metabolize plant toxinsthrough the high number of metabolic enzymes, including glutathione S-transferases (GST) andcytochrome P450s. In Canada, soybean Glycine max L. (Fabaceae) is a high value crop whichexperiences damage from several herbivores. TSSM is predicted to be a progressively importantpest due to increasing temperatures with climate change. This study examined the ability ofTSSM to adapt to soybean host plant defenses, isoflavonoid and flavonoid leaf compounds, andhow this information can be applied to manage this pest. A comparison of TSSM fecunditybefore and after 10 generations of selection on 4 soybean cultivars with varying genestein andkaempferol levels determined that non-adapted mites on the resistant cultivars produced fewereggs than mites adapted to the susceptible cultivars. P450 activity was significantly higher inTSSM on resistant cultivars compared to mites adapted to susceptible cultivars. In summary,spider mites reared on soybean with varying levels of resistance showed different patterns ofadaptation depending on cultivar.