Abstract

Variation in bread making quality of wheat (Triticum aestivum L) is a major consideration for suppliers and bakers. Grain protein concentration, protein quality, ash content and carbohydrates are major quality attributes of bread wheat. Breeders and their cereal chemist colleagues use predictors of these end use quality factors in the early generations to develop improved cultivars. Six populations of bread wheat derived from a previous diallel experiment were evaluated under three rates of nitrogen fertilizer for grain yield and end use quality. Increasing nitrogen (N) rates from low (40 kg fad^-1. N)  to high (120 kg fad^-1. N) had an accelerating significant effect on grain yield and quality in F₂ and F₃generations. Desirable quality types along with high grain yield were defined within the C3, C4 and C6 populations. The population C6 exhibited the highest flour protein (13.8%) and the lowest flour ash (0.42%) as well as good grain yield as compared with the check variety and other populations. In F₃ populations, 1000-kernel weight was an effective selection criterion for grain yield in pop. C3, C4 and C6 but it caused reduction in flour protein in pop. C1. Grain protein concentration showed an increasing trend in F₃ generation, confirming the positive relationship with grain yield. The expected response to selection of F₃ populations under high N level were  8.81% for grain yield, 8.0% for flour protein 5.74% for gluten and 4.98% for carbohydrates. The SDS-PAGE of grain storage proteins was performed in order to analyze molecular weight of gluten subunits (GS) and investigate genetic diversity among the selected populations. The population C6 exhibited the highest unique bands (5 from 7 bands) under high N level and followed by the population C4. The high N level generally increased total high-molecular weight-GS content in wheat grain, although different patterns of response to N rate were observed between populations.

Key words: Bread wheat, segregating populations, nitrogen, protein electrophoresis.