Microwave Characterization of Hydrophilic and Hydrophobic Plant Pathogenic Fungi Using Open-Ended Coaxial Probe

Plant diseases have a direct impact on agricultural food production. The time required to detect the pathogen plays a crucial role to minimize the fungal-induced disease damage in crops. Current microbial detection techniques take several days to identify the disease. Microwave detection techniques have proven to be a good candidate in identifying pathogens. Microwave dielectric characterization based on an open-ended coax technique is proposed to electrically characterize pathogens having potential applications in plant diseases. Seven common fungi growing on major crops in the United Arab Emirates were isolated and cultured in the lab. A microwave dielectric assessment kit, based on the open-ended coax technology, was used to obtain the dielectric properties of samples. Our data demonstrated a distinct variability between soil- and air-borne pathogenic fungi. Thus, individual fungi can be identified based on their specific microwave dielectric signature. Factors such as conidial sporulation and hyphal growth and polarization of these fungi may attribute to these electric discrepancies. Dielectric spectroscopy modeling based on the Havriliak-Negami model was used to help to understand the molecular structure interaction with the high-frequency signal. This paper revealed a significant dielectric contrast behavior variation among all seven fungi. This paper also supported previous results obtained by other researchers, which classified fungi into two main groups, namely hydrophilic and hydrophobic. Nonetheless, the fungus Alternaria solani has different behavior from this classification. This research is the first to demonstrate the ability of dielectric microwave characterizations tests to facilitate rapid diagnosis and appropriate treatments of plant diseases.