GGE biplot analysis is an effective method, based on principal component analysis (PCA), to fully explore multi-environment trials (METs). It allows visual examination of the relationships among the test environments, genotypes and the genotype-by-environment interactions (G×E interaction). The objective of this study was to explore the effect of genotype (G) and the genotype × environment interaction (GEI) on the grain yield of 20 chickpea genotypes under two different rainfed and irrigated environments for 4 consecutive growing seasons (2008–2011). The yield data were analysed using the GGE biplot method. The first mega-environment contained environments E1, E3, E4 and E6, with genotype G17 (X96TH41K4) being the winner; the second mega-environment contained environments E5, E7 and E8, with genotype G12 (X96TH46) being the winner. The E2 environment made up another mega-environment, with G19 (FLIP-82-115) the winner. The mean performance and stability of the genotypes indicated that genotypes G4, G16 and G20 were highly stable with high grain yield.
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.
To study the properties of some drought tolerance criteria and agronomic characters in wheat, an eight-parental diallel cross, excluding reciprocals, was grown in a randomized complete block design with three replications under two different water regimes (irrigated and rainfed) for two years in the College of Agriculture at Razi University, Kermanshah, Iran. High broad-sense heritability estimates were observed for harvest index, grain yield, and earliness. Additive gene action was found to be predominant for grain yield, harvest index, relative water content and chlorophyll fluorescence. The results of combining ability analysis revealed that Plainsman was the best general combiner and Plainsman × Kobomugi was the best specific combination for improving drought tolerance. The pooled analysis of variance for combining ability over rainfed conditions reflected that the GCA × environment interaction was not significant for harvest index and chlorophyll fluorescence, and the SCA × environment interaction was non-significant for relative water content and relative water loss, indicating that genes controlling osmoregulation and the other physiological traits mentioned are not affected in these varieties by different rainfed conditions and hence show static stability.
To evaluate the repeatability of yield-based drought tolerance indices over years, twenty chickpea genotypes were evaluated using a randomized complete block design with three replications for four cropping seasons (2008–2012) in the experimental field of Razi University. The result of combined analysis of variance for seed yield showed significant differences for location (L) (rain-fed and irrigated), genotype (G), and LY and GL interactions, indicating the presence of genetic variability and the possibility of selection for stable, drought-tolerant genotypes. Principal component analysis (PCA) based on the Spearman's rank correlation matrix was used to visualize the relationships between different drought tolerance indices. Due to their positive significant correlation with seed yield under both conditions over four cropping seasons, the stress tolerance index (STI) and geometric mean productivity (GMP) were identified as desirable criteria for the selection of drought-tolerant genotypes under severe stress conditions. The selection of drought-tolerant chickpea genotypes using these indices in a one-year trial will mirror the results of multiple cropping season trials. According to the Spearman's rank correlation coefficients between single vs. single years and single vs. the mean of multiple years, the tolerance index (TOL), mean productivity (MP), abiotic tolerance index (ATI), stress susceptibility percentage index (SSPI) and modified stress tolerance index (K1STI) were identified as repeatable indices under severe drought conditions.
The genotype by
environment (GE) interaction is a major problem in the study of quantitative
traits because it complicates the interpretation of genetic experiments and
makes predictions difficult. In order to quantify GE interaction effects on the
grain yield of durum wheat and to determine stable genotypes, field experiments
were conducted with ten genotypes for four 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 exhibited
significant differences for the GE interaction, indicating the possibility of
stable entries. The results of additive main effect and multiplicative
interaction (AMMI) analysis revealed that 12% of total variability was
justified by the GE interaction, which was six times more than that of
genotype. Ordination techniques displayed high differences for the interaction
principal components (IPC1, IPC2 and IPC3), indicating that 92.5% of the GE sum
of squares was justified by AMMI1, AMMI2 and AMMI3, i.e. 4.5 times more than
that explained by the linear regression model. The results of the AMMI model
and biplot analysis showed two stable genotypes with high grain yield, due to
general adaptability to both rainfed and irrigated conditions, and one with
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.
Authors:E. Farshadfar, - Ghanadha, J. Sutka and M. Zahravi
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 F1 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.
In order to locate QTLs controlling field and laboratory indicators of drought tolerance, chromosome addition lines of Agropyron elongatum (donor) in the genetic background of Chinese Spring (recipient) were tested in the field and laboratory of the College of Agriculture, Razi university, Kermanshah, Iran. The plant genetic material was cultivated in the field and laboratory under two different water regimes (irrigated and non-irrigated). High significant differences were found for promptness index (PI), coleoptile length (CL) and root length (RL) under stress and non-stress conditions, indicating the presence of genetic variation and the possibility of selection for these traits. High correlation coefficients were found between PI, germination stress index (GSI) and stress tolerance index (STI), displaying a high association between the indices of field and laboratory predictors of drought tolerance. Field and laboratory predictors of drought tolerance showed that most of the QTLs controlling drought tolerance criteria in Agropyron are located on chromosomes 3E, 5E and 7E, which collectively constitute 84.3% of the additive genetic variance.
Authors:E. Farshadfar, R. Mohammadi, M. Aghaee and J. Sutka
Water deficiency is a major constraint in wheat production and the most important contributor to yield reduction in the semiarid regions of the world. species related to wheat are valuable genetic sources for different traits including resistance/tolerance to biotic and abiotic stresses. To locate the genes controlling the physiological and agronomic criteria of drought tolerance, disomic addition lines of secale cereale cv. Imperial (donor) into the genetic background of Triticum aestivum cv. Chinese Spring (recipient) were tested under field, greenhouse and laboratory conditions. Disomic addition lines exhibited significant differences for relative water content (RWC), relative water loss (RWL), water use efficiency (WUE) and stomatal resistance (SR), indicating the presence of genetic variation and the possibility of selection for improving drought tolerance. Three physiological variables, RWL, WUE and SR, with high correlation with the stress tolerance index (STI) and germination stress index (GSI), contributed 69.7% to the variability of yield under stress (Ys) in the regression equation. Based on the physiological multiple selection index (MSI) most of the QTLs controlling physiological indices of drought tolerance were located on chromosomes 3R, 5R and 7R. The contribution of addition line 7R to the MSI was 47%. The evaluation of disomic addition lines for STI and GSI revealed that most of the QTLs involved in these quantitative criteria of drought tolerance are located on 3R and 7R. Cluster analysis and three dimensional plots of Ys, yield potential (Yp) and MSI indicated that 3R and 7R are the most important chromosomes carrying useful genes for improving drought tolerance.