screening of rice genotypes by some morphological and physiological traits under drought stress condition

background and objectives: rice plant requires abundant water during its growth cycle and usually faced with water deficit. drought  stress alters the allocation assimilate , root and shoot growth during the vegetative period and also lower tillering, death tillers, lower plant height and flowering delay. the aim of this study was to screen different iranian genotypes and some lines from irri with identify the morphology and physiology traits such as drought tolerance mechanisms in order to select drought tolerant genotypes.  material and methods:treatments (56 rice genotypes) were arranged in completely randomized block design in two growth conditions including full irrigation and drought stress at seedling stage in rice research institute of iran, deputy of  mazandaran (amol) in 2013 . some morphological and physiological traits including leaf relative water content (rwc), spad value, leaf color (lc), plant height, leaf area and number per plant, root and shoot dry weights, root length, membrane electrolyte leakage (mel) and ph were measured. results: results showed that all traits in both well watered and stress conditions as well as genotype× environment (g*e) interaction were significantly different. in comparison with the other characters, rwc (17.3%), root dry weight (28.2%) and shoot dry weight (21.9%) were reduced while mel (86%) was increased in stress conditions. correlation results showed that root and shoot dry weights were significantly correlated with plant total dry weight in stress conditions. conclusion:  genotypes  with better performance in stress conditions were selected as drought tolerant genotypes. these genotypes are including tarom-mahalli, tarom-deylamani, neda, fajr, shafagh, tabesh, koohsar, gohar, hamr, anboori-ghermez, doroudzan, zayanderoud and firuzan from iranian local and improved varieties as well as seven improved lines from irri.