Evaluation of Seedling Stage and Identification of Appropriate Selection Criteria in an Rice Segregating Population (Oryza Sativa L.) under Salinity Stress Condition

The objective of present research was investigating the effects of salinity stress on rice seedling characteristics in order to identify appropriate selection criteria for selecting genotypes in seedling stage under salinity stress conditions. A population of 150 F4 families derived from a cross between two Iranian cultivars، Sepidrood and Gharib has been evaluated in controlled conditions by electrical conductivity of 12 dS m-1 in seedling stage. Analysis of variance showed significant differences between all families for all of the studied traits that were implicated high genetic diversity among families. Calculation of the correlation coefficient revealed high correlation coefficient of phenotyping and genotyping between biomass and shoot dry weight and، therefore، root dry weight and shoot fresh weight had high correlation with biomass، but standard tolerance ranking that was tolerance indices to salinity stress had negative and significant correlation with biomass. Stepwise regression analysis indicated that shoot and root dry and fresh weight had the greatest effects in explanation of lines biomass changes، respectively، so that they canexplain 97% of phenotypic variation for biomass. Path analysis showed that shoot dry weight had high direct effect and thus، it can be introduced as an appropriate selection index to increase biomass and selectinglines for improved salt tolerance. Also، factor analysis revealed five main factors that can explain 84. 7% of the total variation among genotypes. Generally، the results of present study indicated that shoot and root dry and fresh weight were more important for producing higherbiomass in salt stress conditions at seedling stage and traits such as standard tolerance ranking، root length، chlorophyll، shoot Na+ concentration، K+ concentration، shoot Na+/K+ ratio and shoot lengthwere lower important for selecting salt tolerant lines at rice seedling stage.