Evaluation of salt tolerance in rice (Oryza sativa L.) cultivars and lines with emphasis on stress tolerance indices

To investigate salinity tolerance at seedling stage, seventeen landrace and improved genotypes of rice (Oryza sativa L.) were assessed in a factorial experiment based on randomized complete block design with three replicates. Four salinity levels (1.19, 4, 8 and 12 ds.m-1) was applied in the early stage of vegetative growth. Results showed that the genotypes were significantly different for salinity tolerance score. Morphological characteristics such as stem (SL) and root (RL) length, dry weight of stem (SDW) and root (RDW), root to shoot length (RL/SL) ratio and vegetative biomass (Bi) were measured. Significant differences (P< 0.01) among genotypes were observed on all studied traits, indicating genetic variation among the genotypes. Mean comparisons among genotypes showed that root and shoot length decreased with increasing salinity levels. The highest and lowest shoot length belonged to Shahpasand and Hasansaraei varieties, respectively. Salinity tolerance indices showed that the highest value of STI, MP, GMP and HM belonged to Shahpasand, Sangjo and Line 4. Results of correlation coefficients among the indices and principle component analysis showed that STI, GMP and HM indices were the most suitable resistance indices. Also, results of principle component analysis and cluster analysis for clustering the studied genotypes by using of these indices exhibited that Shahpasand and Line 416 were most tolerant to salinity stress at seedling stage among the studied genotypes.