Utilization of image-based spectral reflectance to detect herbicide resistance in glufosinate-resistant and –susceptible plants: A proof of concept


 Glufosinate is an effective postemergence herbicide and overreliance on this herbicide for weed control is likely to increase and select for glufosinate-resistant weeds. Common assays to confirm herbicide resistance are dose-response and molecular sequencing techniques; both can require significant time, labor, and a unique technical equipment and skillset to perform. As an alternative, we propose an image-based approach that uses a relatively inexpensive multispectral sensor designed for unmanned aerial vehicles to measure and quantify surface reflectance from glufosinate-treated leaf discs. Leaf discs were excised from a glufosinate-resistant and –susceptible corn (Zea mays L.), cotton (Gossypium hirsutum L.), and soybean [Glycine max (L.) Merr.] varieties and placed into a 24-well plate containing eight different concentrations (0-10 mM) of glufosinate for 48 hours. Multispectral images were collected after the 48-hour incubation period across five discrete wavebands; blue (475-507nm), green (560-587 nm), red (668-682 nm), red edge (717-729 nm), and near-infrared (842-899 nm). The green leaf index (GLI [metric to measure chlorophyll content]) was utilized to determine relationships between measured reflectance from the tested wavebands from the treated leaf discs and the glufosinate concentration. Clear differences of spectral reflectance were observed between the corn, cotton and soybean leaf discs of the glufosinate-resistant and -susceptible varieties at the 10 mM concentration for select wavebands and GLI. Leaf discs from two additional glufosinate-resistant and –susceptible varieties of each crop were subjected to a similar assay with two concentrations: 0 and 10 mM. No differences of spectral reflectance were observed from the corn and soybean varieties in all wavebands and the GLI. The leaf discs of the glufosinate-resistant and –susceptible cotton varieties were spectrally distinct in the green, blue, and red-edge wavebands. The results provide a basis for rapidly detecting glufosinate-resistant plants via spectral reflectance. Future research will need to determine the glufosinate concentrations, useful wavebands, and susceptible/resistant thresholds for weeds that evolve resistance.