Sources of variation for yield, protein content and hectolitre mass of spring wheat (Triticum aestivum L.) cultivars of the Western and Southern Cape

In the Western and Southern Cape the quality of wheat varies annually due to variable climatic conditions. This holds a commercial risk to the milling and baking industries in delivering the refined products to their respective clients. It is, therefore, important to classify cultivars and localities according to their ability to produce high quality bread wheat grain. In this study, similar production techniques were used to grow seven spring wheat cultivars at nine localities for the period 1992 to 1995. AMMI analyses were used to describe the effect of genotype, environment and their interaction on grain yield, kernel protein content and hectolitre mass. Environment was found to be by far the most important parameter of variance. No significant genotype x environment interaction was found for grain yield. Although cultivars differed in their yield potential, genotype as a main effect contributed only 1.3% to the variation in yield when compared to 90.7% for environment. Significant genotype x environment interactions were found for grain protein content and hectolitre mass. Cultivars such as Palmiet, Nantes, SST16 and to a lesser extent Adam Tas, showed considerable sensitivity to both high and low protein areas, indicating a lack in stability for this parameter. Annual variation in rainfall during the grain filling period dominated environmental variation for hectolitre mass, making it almost impossible to classify cultivars and regions according to their ability to produce high hectolitre mass.Articl

Sources of variation in spring wheat (Triticum aestivum L.) cultivars of the Western and Southern Cape. II. Baking characteristics

Protein content and quality determine flour quality, as well as the success of bread-baking. The stability of wheat quality characteristics is of great importance to the milling and baking industry, who have to produce an end product of acceptable and consistent quality to the consumers. It is, therefore important to classify cultivars and production regions according to their ability to produce high quality wheat grain. Seven spring wheat cultivars were grown at nine localities for the period 1992 to 1995 for the purpose of this study. The effect of cultivar, environment and their interaction on water absorption, Alveograph characteristics and loaf volume were described by AMMI (Additive Main Effects and Multiplicative Interaction) analyses. Environment was found to be by far the most important contributor to variance for all the characteristics determined. Except for water absorption, where the effect of cultivar was not significant, cultivar, environments, as well as cultivar x environment interaction, significantly affected all these characteristics. SST16 showed considerable cultivar x environment interaction for water absorption, Alveograph W-value and loaf volume, indicating a lack in stability for these parameters. Adam Tas, on the other hand, showed sensitivity for the Alveograph characteristics. This tendency may be ascribed to the effect of cultivar x environment interaction on grain protein content. Cultivar reaction may, therefore, differ from year to year at the same locality.Articl

Sources of variation in spring wheat (Triticum aestivum L.) cultivars of the Western and Southern Cape. I. Milling and dough development characteristics

Approximately 90% of the annual wheat crop produced in the Republic of South Africa is milled into flour for bread-baking purposes. The percentage of flour extracted, as well as the dough development properties, determine the milling and dough mixing characteristics. In an increasingly deregulated market environment, these quality characteristics largely determine the price of the wheat. The ability of cultivars and localities to produce high quality wheat grain must, therefore, be classified. Seven spring wheat cultivars were grown at nine localities for the period 1992 to 1995. Similar production practices were followed at all localities. AMMI (Additive Main Effects and Multiplicative Interaction) analyses were used to describe the effect of cultivar, environment and their interaction on flour extraction yield, Falling Number, gluten, as well as Mixograph dough development time, peak height and band width. Environment was found to be the most important contributor to variance for all characteristics determined. No significant cultivar x environment interaction was found for flour extraction yield. Cultivar as a main effect contributed only 2.5% to the variation in flour extraction, while that of environment was 68.7%. Significant cultivar x environment interactions were found for Falling Number, gluten content, dough development time, peak height and band width. Interactions were particularly strong for cultivars such as Palmiet and Adam Tas in the case of Falling Number and gluten content, indicating a lack in stability in these properties. Nantes, SST 55 and to a lesser extent SST 16 and SST 66, showed considerable sensitivity with regard to dough development time, peak height and band width. Cultivar reaction over years may, therefore, vary considerably at the same locality. It is thus almost impossible to classify cultivars and localities according to these characteristics.Articl