Differential Responses of some Rice Genotypes to Drought Stress at Different Growth Stages

Water deficiency is one of the major abiotic stresses which adversely affect rice production. Four rice genotypes; Giza177, IR64 (sensitive), Vandana and Orabi3 (tolerant) were used to study the mechanics by which rice genotypes acquire the drought tolerance. Shoot and root lengths, fresh and dry weights, cell membranes stability as lipid peroxidation as MDA content and rate of electrolyte leakage (EL) were measured as indices for drought tolerance. Total protein analysis and differential display RT-PCR were carried out at different growth stages to study the response of the tested genotypes to drought stress. All determinations were carried out under both normal irrigation (control) and drought stress conditions. Our results indicated that drought tolerant genotypes showed different response through DD-RT-PCR than sensitive genotypes. Changes in protein profile as increasing in band number and intensity were associated with the up regulation or even induction of some RNA transcript in tolerant genotypes. Our data conclude that vegetative growth stage was the most stable under drought stress of all studied genotypes. Analysis of induced RNA followed by DD-RT-PCR to characterize genes may involve in drought tolerance mechanism need further investigation.