Biotechnological Approaches for Genetic Improvement of Sorghum
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Sorghum (Sorghum bicolor L., Moench) is the fifth most important cereal crop in the world and represents an important source of food, feed and energy in several countries. Recently, there has been an increasing interest in sorghum cultivation worldwide, since it is relatively more drought- and heat-tolerant than other cereal crops, and it is better suited for the predicted consequences of global warming. In Africa and Asia, sorghum is primarily used as food for more than 500 million people, while in the Americas and Australia, it is used mainly as a maize-substitute in livestock feed. In the United States, sorghum is also being used in the production of ethanol. In view of its diverse utility, sorghum offers a large number of target traits that could be modified to meet the required applications. In this work, we have used different genetic engineering approaches to address two important issues in sorghum: seed quality and nitrogen use efficiency. First, we examined the temporal and spatial activity of a rice glutelin gene (GluA-2) promoter, in transgenic sorghum. Results from quantitative and histochemical GUS assays, as well as from transcript analyses, showed that this promoter is highly active during the middle stages of sorghum seed development and that it controls transgene expression specifically in the seed endosperm. This means that the GluA-2 promoter can serve as a useful tool in introducing novel traits into sorghum seed in order to improve the quality of this important cereal. Furthermore, we investigated the effects of cytosolic glutamine synthetase (GS1) and alanine aminotransferase (AlaAT) gene overexpression on nitrogen metabolism and plant growth in sorghum. T_(2) generation plants transformed with a sorghum GS1 gene (Gln1) driven by the maize ubiquitin promoter exhibited enhanced grain yield and biomass accumulation under optimal nitrogen levels.
Urriola Simons, Jazmina Itzel (2013). Biotechnological Approaches for Genetic Improvement of Sorghum. Doctoral dissertation, Texas A & M University. Available electronically from