Salicylic acid improves tolerance against salt stress through boosting antioxidant defense system in black bean.

To evaluate the effect of salicylic acid (SA) on seed germination of black bean plant under saline conditions, seeds were primed with salicylic acid (0, 2, 10, and 20 mM) and germinated under salt stress (0, 50, and 100 mM NaCl). The measured parameters included the percentage and rate of seed germination, seedling length and dry weight, malondialdehyde and hydrogen peroxide levels, and activity of catalase, ascorbate peroxidase and guaiacol peroxidase in the seedlings. Results showed the values of germination indices decreased with increasing the level of salt stress. However, SA priming (10 mM) alleviated the harmful effects of salt stress in black bean. SA increased seed germination percentage by 72% and 45% at 50 and 100 mM NaCl respectively, compared to the control condition. Germination rate augmented by 33% (at 50 mM NaCl) and 60% (at 100 mM NaCl) by SA priming compared to the seeds exposed to salt stress alone. Seedlings dry weight (+ 51% at 50 mM and + 34% at 100 mM) and length (+ 57% at 50 mM and + 29% at 100 mM NaCl) were significantly higher by priming with 10 mM salicylic acid, compared to exclusively salt stress-treated seeds. SA priming increased antioxidant enzymes activities and decreased the levels of lipid peroxidation and hydrogen peroxide in salt stressed black bean seedlings. In conclusion, salicylic acid priming (particularly at 10 mM) enhances salt tolerance in black bean via lessening of oxidative stress.