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 (NH 4 NO 3 ; 550, 825 or 1650 mg/L), potassium nitrate (KNO 3 ; 633.3, 950 or 1900 mg/L), calcium chloride dehydrate (CaCl 2 ·2H 2 O; 147, 220 or 440 mg/L), potassium dihydrogen phosphate (KH 2 PO 4 ; 57, 85 or 170 mg/L), magnesium sulfate heptahydrate (MgSO 4 ·7H 2 O; 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 NH 4 NO 3 , 1900 mg/L KNO 3 , 220 mg/L CaCl 2 ·2H 2 O, 170 mg/L KH 2 PO 4 , 370 mg/L MgSO 4 ·7H 2 O 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 NH 4 NO 3 . 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.