Determining the most Tolerant Genotypes of Hashemi Rice Mutant (M3) in Response to Drought Stress using of Physiological Growth Indices and Enzymatic Changes

 Abiotic stresses, especially drought, have a negative effect on crop growth and production. Plants display a variety of hysiological and biochemical responses both at the cellular and whole organism level upon sensing drought stress. Drought tolerance levels and antioxidant protection mechanisms were evaluated for 41 mutant genotypes seedlings (M3) induced of the ethyl methanesulfonate on Hashemi rice cultivar.

Drought was imposed in hydroponic culture with polyethylene glycol 6000 (PEG 6000) at the level of -10 bar using factorial experiment as completely randomized design. In this experiment the morphological characteristics of relative humidity content, electrolyte leakage, proline and antioxidant enzymes were investigated.

 All the studied genotypes showed apparent decreases in growth characteristics under drought stress. Based on different morpho- physiological parameters, two genotypes M29 and M122 were identified as promising drought tolerant mutant genotypes. They exhibited the maximum increase in root length without any significant changes in its root weight and root volume compared with the parent under stress and also showed better performance for various physiological parameters such as relative water content, cell membrane stability and proline content upon water stress under hydroponic conditions. Concomitantly, the activity of antioxidant enzymes catalase, peroxidase and ascorbate peroxidase in the drought-tolerant mutant genotypes increased markedly during drought stress, while decreased by drought stress in the drought sensitive mutant genotypes. Also, M31 and M106 mutant genotypes were introduced as the most susceptible genotype with minimum performance at stress level.

 In this study it was found, proline accumulation, increase of root biomass, increase of membrane stability and antioxidant enzymes such as POX, APX and CAT during water stress are contributing to drought tolerance conditions and could be used in screening for drought tolerance. The mutant genotypes identified in this study will be useful for further dissection of water stress tolerance in rice.