Identification of drought tolerant barley genotypes (Hordeum vulgare L.) using drought tolerance indices

Drought stress affects 40-60% of agricultural lands all over the world(Bray, 2002). Having 240 mm precipitation, Iran is located in arid and semi-arid parts of the word. Due to shortage of rainfall in Iran, a big share of crop breeding is devoted to drought tolerance. It has been resulted in stable varieties. Although barley is more tolerant to drought stresscompared to other cereals, however it is susceptible to moisture shortage during tillering and grain formation which would result in yield losses (Nevo and Chen, 2010). Yield is the most direct index for evaluation of response to stress. Although grain yield is affected by environmental factors but it is an index to evaluate response of cereals to environmental stress. The propose of drought tolerant genotypes is to provide relatively tolerant varieties so that showing less yield losses compared to other genotypes. Different yield based indices have been suggested. All these indices consider yield under two condition that is stress and no stress (Fernandez, 1992).
Material and twenty varieties and promising lines of barley were compared in a randomized complete block design with three replication under two irrigation conditions (normal and water lack after 50% of ear emergence).The experiment was carried out at research station of Torogh for two years. Farm preparation, cultivation and sowing were implemented as standard protocol for experiment. Under normal condition, 3-4 irrigation ere applied according to crop water demand while irrigation was cut after 50% of ear emergence under stress condition. Stress tolerance indices were calculated based on two years means which areMP, GMP, STI, SSI, TOL, YI, YSI, RDI. Data were analyzed and Duncan mean comparison as done (SAS 9.1.3.).Biplot analysis was adopted by GEA-R software.
Result and applying GIBplot based on studied indices made it easy to compare genotypes. There was no significant difference between yield correlations under normal and stress conditions. Genotype*environment interaction was significant over two years of experiments which shows provoking high level of stress. Blum (1999) and Panthuwan et al. (2002), belived that potential yield could only affect yield under normal condition or low stress but under highly stress, genotype*environment interaction would significantly decide level of crop yield.Biplot correlation equations could explain relation between grain yield and calculated indices where GMP, MP and STI were the best ones under both conditions. Lines 6, 20 and 15 were identified as superior gentypes based on GIBplot polygon. Keeping in view both yield and stability adopting GGEBIplot same results were obtained. Line 6 was ideal genotype in biplot. Results showed that GIBplot and GGEBiplot were suitable methods for identifying superior genotypes based on biplot indices considering both yield and stability