In order to determine stable bread wheat genotypes with high grain yield via a single parameter, field experiments were conducted with 20 genotypes for 4 consecutive years in two different conditions (irrigated and rainfed) in a completely randomized block design with three replications in each environment. Combined analysis of variance showed highly significant differences for the GE interaction indicating the possibility of selection for stable entries. The results of additive main effect and multiplicative interaction (AMMI) analysis revealed 10% of total variability was justified by the GE interaction which was 2.5 times more than that of genotypes. Ordination techniques displayed high differences for the interaction principal components (IPC1, IPC2 and IPC3), exhibiting that 83% of the GE sum of squares was justified by AMMI1, AMMI2 and AMMI3, i.e., 3.77 times more than that explained by the linear regression model displaying the relative efficiency of AMMI1 model in comparison with regression model. AMMI stability value (ASV) discriminated genotypes G6, G9, G14, G15, G17 and G18 as the stable entries. As stability per se is not a desirable selection criterion, because the most stable genotypes would not necessarily give the best yield performance, hence, simultaneous consideration of grain yield and ASV in a single non-parametric index entitled: Genotype Selection Index (GSI), discriminated G6 and G17 with general adaptability and high grain yield for rainfed and irrigated conditions which was in agreement with the results of biplot analysis.

In order to locate QTLs controlling the phenotypic stability and drought tolerance of yield and yield components in barley, seven disomic addition lines were sown together with their parents (donor and recipient) in a randomized complete block design with three replications under four rainfed and irrigated conditions. The descriptive diagram of yield and yield components exhibited a genotype (G) × environment (E) interaction and moderate variability over different environments, indicating the possibility of selection for stable and drought-tolerant entries. The AMMI stability value (ASV) and yield stability index (YSI) discriminated addition lines 2H and 4H as the most stable and droughttolerant.Path analysis revealed that the relative contribution of the number of seeds per plant (NSPP) (0.71) to grain yield (GY) was higher than that of the number of seeds per spike (SPS) (−0.44) and of thousand-seed weight (TSW) (-0.14). Therefore, the contribution of NSPP to the stability of GY over different environments was higher than that of other yield components. In other words, the instability of GY was caused by TSW and SPS in different environments. Path analysis on the drought susceptibility index revealed that most of the QTLs controlling drought tolerance and drought susceptibility in barley are located on chromosomes 3H and 6H, respectively.

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To evaluate the genetic background of quantitative criteria of drought tolerance in wheat, six generations of a cross between the varieties of Plainsman and Cappelle Desprez were grown in a randomized complete block design with three replications in the greenhouse of the College of Agriculture of the University of Tehran in 1997.Genetic variation was found for yield potential (Yp), stressed yield (Ys), excised leaf water retention (ELWR), relative water loss (RWL), relative water content (RWC) and harvest index (HI) under water stress conditions.High heterosis and heterobeltiosis were observed in the F 1 hybrid for Ys, HI and spike yield index (SYI). Genetic analysis exhibited overdominance in the inheritance of Ys, RWL, ELWR, HI, biomass and SYI, while RWC and Yp were controlled by the additive type of gene action. High narrow-sense heritability estimates were shown by ELWR, biomass and SYI. The high genetic advance for ELWR, RWC, HI and SYI indicated that direct selection could be effective for these traits. The epistatic effects (additive × additive=[i] for Yp, Ys and RWL, additive × dominance=[j] for ELWR, and dominance × dominance =[l] for RWL) were found to be outstanding.

Six pure lines of maize were tested in a randomized complete block design with three replications under irrigated and rainfed conditions. Genetic variation was found between the genotypes for yield potential (Yp), stress yield (Ys), tolerance index (TOL), geometric mean productivity (GMP), harmonic mean (HM) and stress tolerance index (STI). Stress tolerance index was corrected using a correction coefficient (ki) and thus a modified stress tolerance index (MSTI) was introduced as the optimal selection criterion for drought-tolerant genotypes. The results of three-D plotting indicated that the most desirable genotype for irrigated and rainfed conditions was the genotype K1515, for non-stressed conditions K18 and for stress conditions K104/3, K760/7 and K126/10.