Genotype and Nitrogen Fertilization Influence on the Grain Protein Content in Some Barley Varieties and Lines

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Grain protein content (GPC) is the main quality trait of barley (Hordeum vulgare L.) because this parameter is a decisive component of seed quality for malt industry. Reaching the level of protein concentration required by the raw industry is very difficult, due to the negative correlation with the yield level. Seventeen winter barley genotypes (varieties and breeding lines), created at NARDI Fundulea during 2003-2017, known as having different grain protein contents, were tested with and without nitrogen fertilization in yield trials at NARDI Fundulea in 2014, 2015 and 2016. Weather conditions during the testing period was reflected by the variation of average yield of the trial from 3861 to 7722 kg/ha (unfertilized) and 4748 kg/ha to 9492 kg/ha (fertilized) and of the average grain protein content from 9.6% to 14.8% (unfertilized) and 10.3% to 15.4% (fertilized). Correlation between grain protein content and yield was significantly negative under unfertilized condition in two years (2014 and 2016) and under nitrogen fertilization in 2016 only. The genotypes with higher GPC in the grains and low yield under nitrogen fertilization are not adequate for use in breeding for improved protein content. Positive and negative deviations from the regression of grain protein content on grain yield were found, several varieties and lines combining high yields and high grain protein content and few varieties and lines combining high yields and low grain protein content. Differences between protein contents with and without nitrogen fertilization were smaller in some varieties and new lines and also presented negative deviations. The information obtained in this study might be useful in breeding new varieties combining low grain protein content and high grain yield.