S. M. Miri - Department of Horticulture, Karaj Branch, Islamic Azad University, Karaj, Iran.
M. Rahimi - Nuclear Agricultural Research School, Nuclear Science and Technology Institute, Karaj, Iran.
B. Naserian Khiabani - Nuclear Agricultural Research School, Nuclear Science and Technology Institute, Karaj, Iran
C. Vedadi - Nuclear Agricultural Research School, Nuclear Science and Technology Institute, Karaj, Iran

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 ۲۵, ۳۵ and ۴۵ Gy, and subjected to MS medium containing additional NaCl (۰, ۱۰۰, ۱۲۰, ۱۴۰ and ۱۶۰ mM) for two months (۱st 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 (۲nd salinity stress). Increasing NaCl concentrations resulted to a decrease in growth rate during ۱st salinity stress. Also, irradiated explants had higher survival percentage, shoot number and shoot fresh weight than non-irradiated ones. In ۲nd salinity stress, only the irradiated explants under ۱۶۰ 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 (۳rd 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.

Banana, Gamma-rays, Mutagenesis, In vitro selection, Salinity stress