Salinity is one of the major agricultural global issues, which causes extensive crop loss and economic damage which affecting 8.7% of global land and projected to impact as much as 50% of arable land by 2050. Tomato (Solanum lycopersicum) is classified as moderately salt-sensitive, with moderate salinity (25-50 mM NaCl) slowing germination and seedling growth, which severely reduces stand establishment. Seed priming is a process of controlled hydration that is known to improve stress tolerance. Here, we demonstrate that the seed priming with chitosan improved seed germination, and early seedling growth under salinity stress in tomato. We then optimized the agar medium (0.5% w/v) and chitosan priming dose (0.2% w/v) in a rapid six -well agar plate assay for maximal vigor. At 50–200mM NaCl concentration, the germination percentage and biomass showed steep declines in unprimed seeds. Conversely, chitosan-primed seeds exhibited significantly improved germination rates and seedling vigor indices across all salinity levels. Priming alleviated the salt stress effects well under salt stress: primed seedlings showed high relative water content (RWC), and total chlorophylls increased antioxidant capacity, and increased friendly pressure of osmo-protectants on osmo-protectants (proline) in relation to non-primed control plants. PCA of 12 physiological traits highlighted separation between primed and unprimed treatments when evaluated under a high salinity treatment. To conclude, seed priming with 0.2% chitosan represents an easy and scalable method to enhance early-stage salt tolerance in tomato. Moreover, the novel six-well agar assay platform described in this work is a sturdy and high-throughput platform for screening seed treatment responses against NaCl salt stresses.
