Ethylene response of salt stressed rice seedlings following Ethephon and 1-methylcyclopropene seed priming

Salinity stress is one of the most devastating abiotic stresses affecting rice growth and productivity. Several phytohormones in rice contribute towards salinity response, including ethylene (ET). Furthermore, priming of rice seedlings with different chemicals has revealed new insights in rice stress physiology. Therefore, the hydroponic culture experiment under completely randomized design (CRD) factorial was conducted to study the effects of seed priming with two contrasting chemicals 1-Methylcyclopropene (1-MCP) and Ethephon with respect to ET production under salinity stress levels 0 (control, CK) and 25 mM NaCl (salinity stress, SS) on cultivar Zhongzheyou 1 ( indica ) with five replications. Results revealed that the use of 1-MCP and Ethephon improved overall rice seedling germination and growth as compared to the unprimed one under salinity stress. Early germination rate was found to be higher in the Ethephon primed seedlings. However, the late germination rate, overall seedling vigor index (SVI), total plant dry biomass (higher as 37.8 and 42% in 1-MCP-primed seeds, and 28.1 and 21.3% higher in Ethephon-primed seeds than no primed seeds under both salinity levels), other agronomic traits, and SPAD value were found to be higher in the 1-MCP primed seedlings. Further, the production of reactive oxygen species was comparatively higher in the Ethephon primed seedlings than the 1-MCP-primed seedlings. In addition, evaluation of ET levels and expression profiling (qRT-PCR) of some ET signaling genes revealed that Ethephon priming resulted in elevated ET concentration and upregulated ET signaling genes, including OsACS1 and OsEIN2 . Overall, our results provide a basic idea of the role of rice seed priming with Ethephon and 1-MCP under salinity condition and their effects on the ET interplay. Graphic Abstract Ethylene response of salt stressed rice seedlings following Ethephon and 1-methylcyclopropene seed priming. SG speed of germination, GE germination energy percentage, 3rd and 6th DAS 3rd and 6th day after sowing, FG final germination.