Differential response of an international rice (Oryza sativa L.) collection to drought simulated stress (PEG) at vegetative stage

摘要

Drought is one of the major abiotic stresses that affects different stages of plant growth and development, especially germination and seedling growth. In order to assess drought stress effect on germination and seedling growth of rice, an experiment was performed at three levels of Polyethylene glycol (PEG-6000) (0, -0.6 and -0.8 MPa) on an international rice collection consisted of 93 varieties. Seven drought tolerance indices including STI, SSI, HM, RDI, SSPI, ATI and TOL were used to identify drought tolerant genotypes. The results of variance analysis showed that the effect of genotypes (G), drought stress (D) and G×D interaction were significant for all investigated traits. With increasing of stress level most genotypes showed similar trend of drought response, i.e. reduction in all traits. The results also revealed that dry weight (DW) was less affected than fresh weight (FW), and the shoot weight (SW) was affected more than the root weight (RW), indicating that shoot growth is more sensitive than root growth to drought stress. The highest correlation (0.91) was observed between shoot fresh weight (SFW) and shoot dry weight (SDW), while the least correlation (0.01) was found between germination rate (GR) and root fresh weight (RFW) and root:shoot length ratio (RL:SL). Among the drought-related indices, the highest correlation was observed between STI and plant performance (Z-scores) under both optimal and stress conditions, thus STI can be used as the most suitable indicator for screening drought tolerant genotypes. Based on the results, genotypes #191 (RTS4), #171 (Paraiba Chines Nova) and #164 (Padi Kasalle) showed the highest performance and STI under drought condition, so they have considerable potential to improve drought tolerance in rice breeding programs. In addition, genotypes #136 and #140 with the lowest values of STI were found to be intolerant genotypes to drought stress.