Analysis of Tolerance Indices in Some Rice (Oryza sativa L.) Genotypes at Salt Stress Condition

ABSTRACT: Rice improvement for salt tolerance requires reliable assessment of salt tolerance variability among segregation genotypes. Sixty five genotypes of rice (traditional, improved and promising lines grown in north of Iran conditions) were evaluated under salt condition containing 0, 3, 6 and 8 dS/m levels during 2010. Five salt tolerance indices comprising: stress tolerances (TOL), mean productivity (MP), geometric mean productivity (GMP), stress tolerance index (STI) and stress susceptibility index (SSI) were used. The indices were adjusted based on shoot length and root dry weight under normal and salt conditions. Analysis of variance for shoot length and root dry weight showed that there was a significant genetic variation among genotypes. Cluster analysis of genotypes using Ys, Yp and five other indices categorized genotypes into five groups for both shoot length and root dry weight. Results of cluster analysis distinguished tolerance and susceptible genotypes. It was concluded that the potential of these genotypes to tolerate salt stress was found to high MP, STI and low SSI for both shoot length and root dry weight. Also, based on broad-sense heritability Ys, TOL and MP for shoot length and Ys, TOL and STI for root dry weight can be used as the best indices for breeding program. Also, by cluster analysis based on tolerant indices, all genotypes were segregated into 4 and 3 groups based on both Yp, Ys, MP, GMP and STI and TOL or SSI, respectively. Therefore, genotypes such as IR56, Yosen, 8803, IR58, R3, 8802 and 8810 as tolerant and Abji Boji, IR30, Amol 2, Neda and 8805 as susceptible can be used in breeding programs.