Priming, drying and storage: effects on physiological quality and thermoinhibition of biofortified lettuce seeds

ABSTRACT: Thermoinhibition of lettuce seeds causes losses in seedling production. Priming improves seed performance under stress; however, there are gaps regarding the duration of its effects after drying and storage, as well as methods that preserve tolerance to thermoinhibition. The objective of this study was to evaluate biofortified lettuce seeds subjected to priming, different drying methods and storage periods, in order to identify strategies that maintain the effects of the treatment. Seeds of the UFU 189#2#2#1 genotype were osmoprimed in PEG 6000 (-1.2 MPa) and subjected to the following methods: control, priming without drying (PRM), slow drying (SD), fast drying (FD), thermal shock followed by SD (TSSD) or FD (TSFD), and reduction of moisture content followed by SD (rSD) or FD (rFD). Drying was carried out at 25 °C (slow) and 32 °C (fast) for 48 hours. The seeds were stored for 0, 30 and 60 days. In a second trial, SD, FD, rSD, and rFD were evaluated for 12, 24, 36, and 48 hours. Moisture content, first germination count, germination, emergence, germination and emergence speed indices, and dry mass of seedlings were determined. Slow drying is more efficient in preserving the tolerance to thermoinhibition after storage. Tolerance is maintained after reduction of moisture content followed by SD or FD for up to 12 hours, with fast drying also being feasible up to 24 hours.