**1. Introduction**

Many crops grown in diverse environmental conditions and are subjected to different stress conditions among them drought is the major yield limiting factor in major crops. Food for future generations is challenged by increasing demand and threatened by deteriorating water availability, nearly 23 million hectares of rainfed rice in South and Southeast Asia are drought prone areas. In some states of India, due to severe drought conditions nearly 40% yield loss, amounting to \$800 million is affected. As the Southwest monsoon are irregular it results in moderate to severe drought in rainfed regions, particularly in eastern India, as a result many morphological, physiological and phenological traits have been reported to improve the performance of many crops to challenge the drought condition Drought Tolerance is defined as the capacity of plants to uphold a certain level of physiological activity over the regulation and well fine-tuning of thousands of genes and numerous metabolic pathways to decrease the resulting damage [1, 2].

Various biotic and abiotic environmental factors interfere with the complete genetic potential of crop plant are called stress. Moisture stress occurs when plants are unable to meet evapotranspiration demand. Drought is induced by absence of water due to irregular rainfalls or insufficient irrigation but it can be impaired by

other factors like soil salinity and physical properties and high air or soil temperature. Drought is insufficiency of water availability, including precipitation and soil moisture storage capacity, in quantity and supply the life cycle of a crop to restrict the maximum genetic grain yield possibility of the crop.
