Efficiency of some physiological traits in evaluation of tolerance of barley advanced lines (Hordeum vulgare L.) to terminal drought stress

In order to evaluate the drought tolerance of 19 barley genotypes using physiological traits, an experiment was carried out in randomized complete blocks with 3 replications under non-stress and terminal drought stress conditions at agricultural research station of Islamic Azad University, Ardabil branch in 2016. Non-stress plots were irrigated when available soil water reached to 60% using tensiometer measurements. In drought stress environment, plants were grown in rainfed condition and drought was imposed after flowering stage by a rain exclusion shelter. After exposure of plants to drought stress, Specific Leaf Area (SLA), Excised Leaf Water Loss (ELWL), leaf Relative Water Content (RWC), Stomatal Conductance (Gs), Chlorophyll Fluorescent (Fv/Fm) and Rate of Ground Cover (RGC) were measured in flag leaves of 10 randomly selected plants. Results of ANOVA showed that SLA, ELWL, RWC and GC affected by drought, however Fv/FM and stomatal conductance did not affected. Stress severity index was obtained as 0.45, indicating a moderate drought stress imposed to genotypes. G×E interaction was significant in all of the traits indicating the severity of the drought stress. In non-stress condition, genotype number 13 with 5040 kg/ha, had the highest grain yield. Under drought stress condition, genotypes number 13 and 15 with 2710 and 2550 kg/ha, had the highest grain yield respectively. Based on grain yield of the genotypes in both environments, genotypes number 13, 18(Bereke-54 check), 9, 4, 19 (Makouee check) and 15 had the highest stress tolerance index (STI). Under stress, genotypes number 15, 1, 18, 2, 3, 10, 13, 12 and 9 had the highest RWC, genotypes number 18, 13, 14 and 8 had the lowest ELWL, genotypes number 15, 9, 19, 18, 1, 13, 17, 4, 16, 5 and 12 had the highest Gs, genotypes number 9, 13, 8, 12, 14, 10, 11 and 15 had the highest RGC (early vigor), genotypes number 4, 3, 13, 15, 4, 12, 9, 17, 19, 1 and 11 had the highest SLA. In non-stress condition yield correlated only with RGC this trait was the only trait remained in final regression model and explained the 34.7% of grain yield variation. Under stress condition, yield positively correlated with RWC, SLA, Gs, RGC and negatively correlated with ELWL. In stepwise multiple regression analysis under drought stress condition, Gs, RGC and ELWL remained in final model with 0.489, 0.512 and 0.381 standard partial regression coefficients respectively(as direct effect). These three characters described 69.3% of grain yield variation. Cluster analysis using Euclidian distance by Ward’s method could successfully separate sensitive and tolerant genotypes. In this analysis, genotypes number 1, 4, 9, 12, 13, 15, 17, 18 and 19 were located in superior cluster, having higher Gs, RWC, SLA and lower Fv/FM. Finally genotype number 13 (the most high yielding genotype) had the second, third, fourth and sixth ranks in RGC, SLA, Fv/FM and Gs. The results of this experiment showed that RGC, having the highest correlation with yield and lower genotype × environment interaction can be consider as the most suitable indirect criteria for selection of drought tolerance in barley. Traits such as Gs, ELWL, RWC and SLA can be consider in the next priority, due to significant correlations with yield under drought stress.