Response of Cultivated and Wild Barley Germplasm to Drought Stress at Different Developmental Stages

Little is known about response of root-related traits of barley (Hordeum vulgare L. subsp. vulgare; hereafter, Hvu) and its wild relative H. vulgare L. subsp. spontaneum (K. Koch) Thell. (hereafter, Hsp) to drought stress. Three separate experiments were conducted to assess these traits at germination, vegetative, and reproductive stages. Drought stress significantly reduced germination percentage and rate, primary root number, and shoot and root length of seedlings. Using pot experiment, drought stress reduced shoot dry weight (SDW) and root dry weight (RDW) at vegetative stage but the ratio of RDW/SDW (RSR) increased under this condition. At reproductive stage, SDW, plant height, number of fertile tiller, and relative water content decreased under drought stress, but root length, root volume, RDW, and RSR increased as the intensity of drought increased. For most of the traits the genotype. moisture environment interaction was significant. The effect of drought stress on genotypes was highly dependent to developmental stages and the intensity of water limitation. The wild barley genotypes had more drought tolerance than the cultivated ones. The results of vegetative and reproductive stages poorly matched with the ones from seed germination stage. Two wild barley genotypes from Iran were tolerant to drought stress at both vegetative and reproductive stages and may be used for genetic studies and possible breeding of barley for root-related traits.