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Grain Yield Variation in Malting Barley Cultivars in Uruguay and Its Consequences for the Design of a Trials Network

^a Programa Cultivos de Secano, Instituto Nacional de Investigación Agropecuaria, CC 39173, CP 70000, Colonia, Uruguay
^b Lab. of Plant Breeding, Dep. of Plant Sciences, Wageningen Univ., P.O. Box 386, 6700 AJ Wageningen, The Netherlands

View larger version (14K): [in this window] [in a new window]   Figure 1. Map of Uruguay indicating the position of the test locations: Colonia Suiza (CS), La Estanzuela (LE), Ombúes de Lavalle (OL), Paysandú (PY), Tarariras (TR) and Young (YG).

View larger version (10K): [in this window] [in a new window]   Figure 2. Effect of increasing the number of replicates on the critical percentage difference, CPD (%), for different number of years, considering a trials network with six locations and two sowing dates.

View larger version (10K): [in this window] [in a new window]   Figure 3. Effect of increasing the number of sowing dates on the critical percentage difference, CPD (%), for different number of locations considering a trials network with 3 yr of evaluation and three replicates per trial.

View larger version (13K): [in this window] [in a new window]   Figure 4. Effect of increasing the number of years on the critical percentage difference, CPD (%), for different number of locations considering a trials network with three replicates per trial and two sowing dates.

View larger version (29K): [in this window] [in a new window]   Figure 5. Genotypic main effect plus genotype x environment (GGE) biplots of grain yield for individual years: (a) 1993, (b) 1996, (c) 1997, (d) 1998. The vectors represent the trials grown at Colonia Suiza (CS), La Estanzuela (LEer, LEmd, and LElt = early, medium, and late sowing date, respectively), Ombúes de Lavalle (OL), Paysandú (PY), Tarariras (TR) and YGer and YGmd (early and medium sowing date, respectively). Cultivars are represented by circles. Standard cultivars appear as filled circles. The amount of variation accounted for by the PCA axes is given as a percentage of the total sum of squares for the genotypic main effect and genotype x environment interaction (GEI).

View larger version (17K): [in this window] [in a new window]   Figure 6. Grain yield analysis over years. Genotypic main effect plus genotype x environment (GGE) biplot representation for the two most extreme locations regarding latitude: La Estanzuela (LEer, LEmd, LElt = early, medium, and late sowing date) and Paysandú (PY) during 1991 to 1995. Trials are represented by squares. The last two digits of the trial labels correspond to the year of evaluation. Cultivars are represented by circles. Cultivar names are given for five standard cultivars checks (filled, dark gray) and four widely grown or released cultivars in the period 1991 to 1995 (filled, light gray). Biplot axes are shown for the two most contrasting trials, LE1_95 and PY_95. The amount of variation accounted for by the PCA axes is given as a percentage of the total sum of squares for the genotypic main effect and GE interaction (GEI)

View larger version (8K): [in this window] [in a new window]   Figure 7. Biplot representation of environments following principal components performed on environmental indices. The analysis was performed for the two most extreme locations regarding latitude: La Estanzuela (LEer, LEmd, LElt = early, medium, and late sowing date respectively) and Paysandú (PY), during the 1991 to 1995 period. Trials are represented by squares. The last two digits of the trial labels correspond to the year of evaluation. The amount of variation accounted for by the PCA axes is given as a percentage of the total sum of squares.

View larger version (13K): [in this window] [in a new window]   Figure 8. Biplot representation following additive main effect and multiplicative interaction effect (AMMI) analysis of grain yield over years. The analysis was performed for the two most extreme locations regarding latitude: La Estanzuela (LEer, LEmd, LElt = early, medium, and late sowing date) and Paysandú (PY). Trials are represented by squares. The last two digits of the trial labels correspond to the year of evaluation. Cultivars are represented by circles. Five check cultivars are depicted by dark gray circles, while four widely grown or released cultivars during the evaluation period are depicted by light gray circles. The amount of variation accounted for by the AMMI axes is given as a percentage of the total sum of squares for genotype x environment interaction (GEI).