Transgenerational stress memory and transgenerational effects caused by wood vinegar and spermidine are associated with early germination of rice seeds under salt stress

The elite glutinous rice cultivar 'RD 6' (RD6), mostly grown in the northeast region of Thailand, suffers from soil salinity resulting in low productivity. Many attempts such as spraying plant growth regulators, and bio-stimulant compounds have been applied to increase stress tolerance and productivity of RD6. However, few studies have focused on transgenerational stress memory (TSM) and transgenerational effects (TGE) of plant growth regulators on the offspring. In this study, seed vigor and germination potential were investigated in RD6 seeds harvested from maternal plants grown under saline field (SSF) which were sprayed at the booting stage with different concentrations of polyamine (spermidine; Spd), bio-stimulant (wood vinegar; WV), combinations of both compounds, and distilled water. In addition, RD6 seeds collected from non-saline field (NSF) were compared. Germination tests under control (0 mM NaCl) and salt stress (100 and 150 mM NaCl) conditions showed that, under salt stress, the germination speeds at the early phase of SSF groups were faster than that of the NSF seeds. The SSF seeds from maternal plants treated with both compounds contained higher contents of polyamine (Spd, and Putrescine; Put) than the SSF group treated with distilled water and NSF seeds. The higher content of polyamine in these SSF seed groups may contribute to the activation of germination. Moreover, faster germination of these seed groups may also be associated with higher H2O2 generation through high H2O2 generation. Moreover, during germination the SSF groups showed better acclimatization to salt stress than those of NSF seeds. These findings indicated that TSM and TGE could promote seed vigor of the offspring leading to enhance germination potential of the seeds under salt stress conditions.