Dielectric analysis of Sclerotinia sclerotiorum airborne inoculum by the measurement of dielectrophoretic trapping voltages using a microfluidic platform

Sclerotinia stem rot, caused by the fungal pathogen Sclerotinia sclerotiorum is a devastating crop disease. Various forecasting systems have been developed to provide information about the risk of outbreaks and thus avoid the heavy financial burden caused by over-spraying fungicides. In this study, we experimentally determine the dielectric properties of Sclerotinia sclerotiorum airborne spores, one of the main agents of infection in stem rot. The dielectric properties of spores are important parameters for the development of forecasting systems based on dielectrophoretic filters as it provides information about the dielectrophoretic response of spores without the need for iterative testing. A microfluidic platform was employed to estimate the dielectric parameters based on a dielectrophoretic method and in media of different conductivities. In addition, using the multi-shell model, spores were modeled using a realistic ellipsoidal double-shell model. To validate the methodology and analysis, the dielectric properties of human embryonic kidney 293 were also determined and compared to values reported in the literature. The obtained values for the electrical permittivity and conductivity of the spore interior and membrane were found to be insensitive to the conductivity of the external medium. On the other hand, the dielectric parameters of the outer most layer showed a small variation with the conductivity of the external medium. This study represents the first report on the dielectric properties of Sclerotinia sclerotiorum airborne inoculum, and it aims to contribute to the development of forecasting systems based on dielectrophoretic filters.