Development of an indirect competitive enzyme immunoassay for detection of a plant elicitor methiadinil

Plant elicitors with distinctive benefits including low toxicity, small application dosages and an innovative mode of action are considered as green agrochemicals by stimulating the host plant immunity. Several new plant elicitors have been developed for tobacco protection against virus attack. Among them, as a milestone in Chinese plant elicitor development, methiadinil (IUPAC: 4-methyl-N-(5-methylthiazol-2-yl)-1,2,3-thiadiazole-5-carboxamide) shows broad application prospects. Because of its low application dosage, its residue determination requires diverse highly sensitive method. Here we developed an indirect enzyme-linked immunosorbent assay (ELISA) method for methiadinil residue determination with the lowest detection limit of 10.69 ng/mL and a linear detection range between 21.84 ng/mL of IC₂₀ and 1513.81 ng/mL of IC₈₀ by a rational hapten designation. Meanwhile, this indirect ELISA method showed good specificity with low cross-reactivity for methiadinil analogue determination and a good correlation with the HPLC method for tobacco sample measurement. This sensitive, rapid and accurate methiadinil residue determination method in tobacco leaves is of great significance for the monitoring of methiadinil in tobacco and guidance for other environmental sample determination and the rational application of methiadinil.