Early detection of root-knot nematode (Meloidogyne incognita) infection by monitoring root dielectric response non-destructively

. The early recognition of root-knot nematode injury belowground is essential in order to avoid serious crop losses. The measurement efficiency of the root dielectric response for detecting Meloidogyne incognita infection non-destructively was tested in potted cucumber and tomato. The electrical capacitance, dissipation factor and electrical conductance of the root, and also the leaf chlorophyll concentration were measured instru-mentally three times during plant growth, this was followed by an evaluation of the root galling intensity after harvest. The electrical capacitance and conductance increased significantly shortly after Meloidogyne infection, this was likely due to the substan-tially enhanced surface area and electrolyte permeability of the root membranes during giant cell formation. The dissipation factor and electrical conductance (related to hydraulic conductance) markedly decreased at the late stage of nematode infection, this was due to restricted root growth and solute uptake caused by the intrusion of giant cells into the root vascular tissues. No serious aboveground pest symptoms were visible in the plants studied owing to the low inoculum density. The results demonstrated the potential of dielectric measurement for the early detection of root-knot nematode infection without plant damage, before the appearance of obvious disease symptoms. This diagnostic tool has the potential to contribute to the improved selection of Meloidogyne -resistant crop genotypes, as well as more efficient nematode control to mitigate economic losses.