Evaluating the drought tolerance of rice genotypes at the seedling stage

Rice is one of the most important agricultural products in Iran and all over the world, drought stress is a significant limiting factor in producing this crop. Breeding for drought tolerance could be an effective method to improve yield and its stability in drought regions. In order to determine the drought tolerance, a factorial experiment based on RCBD with three replications was conducted under hydroponic culture conditions at the plant breeding laboratory of Gonbad-e-Kavous University in 2012. Treatments were 22 rice genotypes and drought stress in 2 levels (control and -5Bar). The studied traits included the root dimension, root weight, root number, root length, stem weight, stem length, genotypic code (the relative tolerance of genotypes to drought stress) and biomass. Analysis of variance showed that there were significant differences (p< 0.01) amongst genotypes in all studied traits, which implies the existence of genetic diversity among genotypes. In cluster analysis based on seedlings traits, genotypes which were in a group with the tolerant cultivar Bala were named as the tolerant group and genotypes that were classified in a group with semi-sensitive Azucena were called as the sensitive group. Results of stepwise regression analysis for biomass as dependent variable and other traits as independent variables showed that stem and root weight had the greatest effect (R2=0.61) on the biomass under drought conditions, respectively. The results showed that there was genetic diversity for studied traits amongst the genotypes and they can be used to improve drought tolerance in high-yielding rice varieties.