**4. Role of genetic transformation in soybean improvement**

Plant transformation has become the most important and reliable technology for the improvement of many crop cultivars, as well as for studying gene functions in plants. In soybean, the technique has already been used to produce genetically modified plants. The genetically modified soybeans range from metabolically engineered plants such as those exhibiting increased oleic acid as well as the herbicide-tolerant (HT) cultivars [26, 27]. Soybean transformation led to production of elite cultivars, increased gene pool, plants with improved secondary metabolites and production of disease free plants, especially regenerated under aseptic culture conditions [2, 28]. As the attempts in soybean transformation progresses, procedures must focus on transgenic plant production exhibiting tolerance to abiotic stress factors. This is so, because soybean growth and productivity is severely hampered by abiotic stress, particularly drought. Drought refers to the absence of rainfall or irrigation for a period sufficient to deplete soil moisture to a level not sustaining plant growth [29]. The decrease in water content completely arrest cell functioning, including the support to plant cell and tissue metabolism, meiotic/mitotic division and differentiation. Some of the reports that have assessed the severity of drought on soybean growth include those of Heatherly [30], Desclaux et al. [31] and Brown et al. [32]. Studies continue to show that the GM soybean varieties have important applications, including the use in biodiesel production. Increased yield emanating from genetic improvement is required for the production of more soybean oil used for manufacturing of biodiesel. Besides the utilisation of soybean oil as a major feedstock for biodiesel production [33], the hull can be used to manufacture ethanol from the significant amount of carbohydrates it contains [34]. All these reports clearly indicate the importance of transformation in increasing yield quantity of high quality. According to Zia [23] and Yu et al. [35] transgenic soybean cultivars account for more than 85% of cultivars cultivated for commercial production worldwide, and the cultivars used still require traits improvements.
