Response of gamma-irradiated banana plants to in vitro and ex vitro salinity stress

Miri, S. M., Rahimi, M., Naserian Khiabani, B. and Vedadi, C. 2019. Response of gamma-irradiated banana plants to in vitro and ex vitro salinity stress. Crop Breeding Journal 9 (1 & 2): 33-44 Stress caused by abiotic factors, such as salinity, decreases production of bananas, because it is very sensitive to salinity. This study aimed to investigate the effect of gamma (γ) ray-induced in vitro mutagenesis as well as in vitro and ex vitro reaction to salt stress (NaCl) in banana (Musa AAA cv. ‘Dwarf Cavendish’). Shoot tips of banana were irradiated with gamma rays at doses of 25, 35 and 45 Gy, and subjected to MS medium containing additional NaCl (0, 100, 120, 140 and 160 mM) for two months (1 salinity stress) as factorial based on completely randomized design with five replications. The surviving shoots were transferred to a salt-free MS medium for one month, and then the salinity stress, as before, was re-applied (2 salinity stress). Increasing NaCl concentrations resulted to a decrease in growth rate during 1 salinity stress. Also, irradiated explants had higher survival percentage, shoot number and shoot fresh weight than non-irradiated ones. In 2 salinity stress, only the irradiated explants under 160 mM NaCl had decreased in shoot number compared to other salinity treatments. In vitro-regenerated plants were rooted and acclimatized in the greenhouse and evaluated under normal and saline conditions (3 salinity stress). A sharp decrease in the survival percentage and leaf number observed with an increase of salinity, while irradiated plants had more survival rate and leaves number than non-irradiated plants. In addition, as the salt concentration increased, the leaf burn and yellowing rate increased and its intensity was higher in non-irradiated plants. Overall, banana shoot tips exposed to different doses of gamma irradiation had higher growth parameters under in vitro and greenhouse salt stress. However, further studies are required to evaluate agro-morphological characteristics of these mutants in the field conditions under salinity stress.