Optimization of medium composition for in vitro shoot proliferation and growth of date palm cv. Mejhoul

The effects of major mineral salts, L-glutamine, myo-inositol and carbon source on shoot bud proliferation of date palm (Phoenix dactylifera L.) cv. Mejhoul were evaluated. Different concentrations of ammonium nitrate (NH4NO3; 550, 825 or 1650 mg/L), potassium nitrate (KNO3; 633.3, 950 or 1900 mg/L), calcium chloride dehydrate (CaCl2·2H2O; 147, 220 or 440 mg/L), potassium dihydrogen phosphate (KH2PO4; 57, 85 or 170 mg/L), magnesium sulfate heptahydrate (MgSO4·7H2O; 123, 185 or 370 mg/L), L-glutamine and myo-inositol (0.5, 1, 1.5 and 2 g/L), sucrose, sorbitol, mannitol or commercial granulated sugar (10, 20, 30, 40 or 50 g/L) were tested. The highest number of shoot buds per explant (18.7) occurred on the medium containing 825 mg/L NH4NO3, 1900 mg/L KNO3, 220 mg/L CaCl2·2H2O, 170 mg/L KH2PO4, 370 mg/L MgSO4·7H2O as well as 1 g/L L-glutamine, 2 g/L myo-inositol and 30 g/L sucrose. The results showed that the frequency of hyperhydricity significantly increased in media containing 1650 mg/L NH4NO3. The concentrations of L-glutamine, myo-inositol and carbon source significantly affected the number of shoot buds per explant. However, they had no effect on hyperhydricity, tissue browning and precocious rooting. Shoots of 4.5-6.0 cm in length were isolated and transferred onto hormone-free media for elongation and rooting. After 3 months, the developed plantlets were successfully transplanted in a glasshouse and over 90 % survived acclimatization.