Document Type : Original Article
In order to improve the shoot proliferation rate of ‘Dwarf Cavendish’ banana shoot tip cultures, polyethylene glycol (PEG6000) was employed at concentrations of 2, 4, and 6% (w/v). The medium without PEG was considered as negative control. An increasing of shoot proliferation was achieved in MS medium containing 2% PEG. Furthermore, application of 2% PEG significantly increased the shoot dry weight (DW) as well as root/shoot DW ratio of the regenerated explants. The root/shoot DW ratio, chlorophyll a and chlorophyll b contents of leaves were decreased by the increase in PEG percentage. Application of PEG at high concentrations increased the leaf tissue chlorosis and necrosis. The proline and potassium contents of leaf tissue were increased in regenerated shoots from the media containing 2 and 4% PEG. Application of 2% and 4% PEG increased ex vitro plantlets survival rate up to 34% and 40%, respectively compared to the control. In conclusion, the mild osmotic stress caused by the application of PEG 2% improved the in vitro shoot proliferation rate accompanied by an increase in the ex vitro survival rate of regenerated plantlets. Seemingly, the promising results using PEG6000 at the resultant level (2%) are in the main part due to the stress simulation effects and later plantlets’ acclimatization through physio-biochemical mechanisms.