Non enzymatic detection of oxalic acid in S.sclerotiorum infected Pea pods

Oxalic acid (OA) is an electroactive chemical marker for the nectrotrophic, fungal pathogen Sclerotinia sclerotiorum, known to cause ‘cottony rot’ in plants. We report here development of an affordable, simple, rapid and easy to fabricate, screen printed electrode (SPE) based electrochemical sensor for the non enzymatic detection of OA. These electrodes are disposable and could be used for one-time rapid assessment of pathogenicity. Cyclic voltammetry is used for carrying out the dynamic measurements. A calibration curve was generated using known concentrations of OA. Further, the sensor applicability is demonstrated by the quantitative detection of OA in real infected plant samples. Judging by the visual inspection least to severely infected Pea pod samples were selected for the study. A highly facile extraction protocol was used to extract OA from these samples. Quantitative estimation of OA in the sample extracts was done using the peak current values and the OA calibration curve. The concentration of OA obtained for the least infected sample was $43.06 \mu \mathrm{M}$ while it increased to $438.99 \mu \mathrm{M}$ for the severely infected sample. Our results corroborate with the fact that OA production increases with the intensity of the S. sclerotiorum infection in the affected plants.