Water stress is the most severe limitation to the productivity of rice. Drought is a meteorological term and is commonly defined as the inadequacy of water availability including period without significant rainfall that affects the crop growth and soil moisture storage capacity. It occurs when the available water in the soil is reduced and atmospheric conditions cause continuous loss of water by transpiration or evaporation. Water deficit is one of the most environmental stresses affecting agricultural production and productivity around the world and may result in considerable yield reduction. Among the crops, rice is probably more susceptible to drought as compare to other crops. Water stress reduces the leaf area, cell size, and intercellular volume. Water is very effective during the life of the rice plant, especially during flowering. In rice cultivation, compared to other crops, water use efficiency is generally low and the amount of water required to produce one kilogram of rice is much higher than others. Therefore, identifying drought-tolerant cultivars is an important key to increase yield and cultivation area.
The aim of this study is to investigate the tolerance of drought stress in rice cultivars based on morpho-physiological traits and grain yield. Therefore, this study tries to evaluate both biochemical and physiological properties and molecular characteristics involved in drought stress conditions in rice. For this purpose, 110 cultivars of Iranian and Central and West Asian countries are cultivated in the control and drought stress sites of Rice Research Institute of Iran, and its morphological and physio-biochemical traits are also measured. Then, all tolerance indicators are evaluated over two years.