Abstract
Date palm (Phcenix dactylifera L.) is moderately tolerant to salinity and drought. However, information about the variation in salinity and drought tolerance among the date palm cultivars is limited. Thus, a method of in vitro propagation via somatic embiyogenesis from shoot tips of date palm cvs. Barhi and Khalas under polyethylene glycol (PEG) induced osmotic stress or NaCl induced salinity stresses was investigated in this study. Highest induction frequencies of embiyogenic calli occurred after 12 months on MS medium supplemented with 10 mg L(-1 )2,4-D, 3 mg L-1 2iP and 2 g L-1 activated charcoal. Optimum MS medium for higher frequency of matured somatic embryos and plant regeneration was recorded using 0.5 mg L-1 NAA, 3.0 mg L-1 2iP of cv. Barhi and 1.0 mg L-1 NAA, 4.0 mg L-1 2iP of cv. Khalas The embiyogenic callus of both cultivars was cultured on different levels of NaCl or PEG-induced stresses after 12 weeks for three subcultures. There were considerable differential responses between date palm cultivars about tolerance to salinity and osmotic stresses. However, the growth of cv. Barhi was completely ceased at levels above 300 mM NaCl or 25 g L-1 PEG while cv. Khalas continued to grow. This indicated that cv. Khalas is more tolerant to high salinity and osmotic stresses than the cv. Barhi. This study also showed that use of tissue callus is an effective way to monitor the response of date palm cultivars to salinity and osmotic stresses. (C) 2018 Friends Science Publishers