Mechanisms of drought stress tolerance in cool season grasses

Drought stress is one of the most limiting abiotic stresses affecting growth, production and survival of plants in many areas of the world, and is expected to intensify considering the trend of climate change. Grass species are important for the sustainability of agricultural systems, forage resources for animal farming and landscapes. Grass species adapt to water deficit by different morphological and physiological responses such as changes in the root growth, photosynthetic pigments, activation of antioxidant enzymes and accumulation of osmotic compounds as well as other specific characteristics, such as summer dormancy, post drought recovery, and persistence, which lead to their drought adaptation following suffering prolonged water stresses. Summer dormancy is one of the important drought avoidance mechanisms in cool-season perennial grasses which lead to decreasing of forage yield during hot and dry summer, and increasing of recovery and survival potential of grasses after suffering from a prolonged drought stress. The results of the studies have indicated that most of plant traits in grasses have high narrow-sense heritability and positive correlation with drought tolerance, therefore can be considered as effective and useful indices in identification and selection of drought tolerance cool seasons grasses genotypes. Using molecular techniques and tools along with the conventional breeding methods in grasses have increased the accuracy and speed of breeding programs for producing drought tolerant cultivars. These techniques in grasses have been instrumental in assessing genetic diversity, molecular identification of paternal parents in the open pollinated populations, determining the gene loci, genome sequencing, and genes associated with drought tolerance.