Pathway to keep seed security: The application of fluorescein to identify true and fake pelleted seed in tobacco

Seed security is one of the key factors to ensure crop production. To protect true seeds from being faked, the uptake pathway of fluorescein into tobacco seed and the effective fluorescent labeling method for anti-counterfeiting in tobacco pellets were investigated in present study. Fluorescein was firstly applied to naked seeds of two tobacco varieties, MS Yunyan85 (MS YY85) and Honghua Dajinyuan (HHDJY), by soaking and powder coating, respectively. After mixing fluorescein (10% of naked seed weight, g) with different pelleting agents, the pelleted seed germination and seedling growth status as well as the fluorescence were investigated. The results showed that there were two uptake pathways of fluorescein into tobacco seed, one was through the seed coat and the other was through emerging seedling tissues after germination occurred. After seed coated with fluorescein powder, the seedling cotyledon tip represented bright green fluorescence under blue light (478 nm) illumination, and the 10:100 (the weight ratio of fluorescein dry powder to the naked seed weight) was considered as the more suitable proportion for treating tobacco seed. In addition, there was the higher vigor index and the lower MDA content in the pelleted treatments with fluorescein compared with the control, and no negative influence was found in the germination percentage, germination index, CAT and SOD activities of the pelleted seeds. Under blue light excitation, fluorescein-labeled pellets displayed bright green fluorescence which was obviously different from the control. Across all pelleting treatments, the method that mixed fluorescein with talc powder could relatively extend the effective time of fluorescein label. It suggested that the fluorescein, a nontoxic fluorescent dye, could be used as an effective anti-counterfeiting label to rapidly and easily distinguishing true (treated) seed from fake (untreated) seed.

► Two pathways of fluorescein uptake into tobacco seed and seedling were proposed.
► Application of fluorescein to pelleted seed of tobacco.
► The bright green fluorescence of fluorescein mainly appeared in the cotyledon tip of seeding.
► The fluorescein represents a potential anti-counterfeiting label to recognize rapidly and easily the true seed in all tobacco pellets.
► Mixing fluorescein with talc powder could relatively extend the effective time of fluorescein label.