GENOTYPIC VARIATION FOR DROUGHT TOLERANCE IN THREE DATE PALM (PHOENIX DACTYLIFERA L.) CUL TIVARS

In vitro genotypic variation in physiological and morphological characters were studied under simulated water stress in three date palm (Phoenix dactylifera L.), cultivars, viz., Sukkary, Berhee and Ruziz. The seedlings obtained from in vitro grown plants were subjected to five stress levels (control, 0.41, -0.82,-1.23,-1.63 MPa) created by adding mannitol to culture medium). The influence of stress on root and leaf number, plant dry matter, relative water contents, photosynthesis, transpiration rate, stomatal and mesophyll conductance, water use efficiency (WUE) and intercellular CO2, were studied. The cultivars responded differently in different morphological and physiological parameters. Water stress significantly decreased root, shoot and total dry weights, intercellular CO2 assimilation rate, relative water contents, transpiration rate and other characters in all the three cultivars. However, weak genotypic variation was observed in almost all the characters. Very strong linear correlation coefficients were observed between total dry weight and photosynthesis (r2 = 0.824), stomatal conductance and photosynthesis (r2 = 0.866) and mesophyll conductance and photosynthesis (r2 =0.94).