Exogenous application of spermidine (SPD) and wood vinegar improves salt tolerance in salt-sensitive rice (ORYZA SATIVA L.)

Spermidine (Spd) and wood vinegar are widely reported for its positive role to ameliorate plants under abiotic stress. In this study, the protective roles of Spd and wood vinegar in salt-sensitive rice cultivars 'Khao Dawk Mali 105 (KDML105)' and 'RD6' exposed to salinity stress were investigated under greenhouse and field conditions by dividing into two experiments. Under the greenhouse condition, three concentrations of Spd (0.1, 0.5 and 1.0 mM) were sprayed daily to 60-dold 'KDML105' plants (booting stage) grown in soil for 7 d ahead of watering the plants with tap water (control) or 30 mM NaCl (salt stress). The results showed that spraying 0.5 mM Spd was most effective in improving the salt tolerance of 'KDML105' as evidenced by an increase in the development of flag leaves, SPAD values, yield and yield components. To reduce crop production cost, the second experiment was conducted. The concentration of Spd used was based on the greenhouse experiment. Exogenous Spd (0.5 mM) was applied in comparison with wood vinegar (1:300 and 1:500) under field condition. Rice 'KDML105' and 'RD6' were grown under low (EC = 3 dS m-1) and high (EC = 10 dS m-1) saline fields. At the booting stage, Spd or wood vinegar were sprayed daily for 7 d. In both saline field sites, both rice cultivars sprayed with Spd and/or wood vinegar at all tested ratios showed a marked increase in yield and yield components, with better results observed for 'KDML105'. The findings suggest that Spd and wood vinegar could be applied for alleviating the effects of salt stress on rice production. (author)