**1. Introduction**

Soybean (*Glycine max* L.) is an important leguminous pulse crop grown for the production of oils and proteins. The legumes include cowpea, lentils, peas, peanuts and other pod producing plants that are cultivated commercially or privately for nutritional, pharmaceutical or industrial purposes. These plants have played a crucial role in the traditional diets of many countries including Brazil, China, India and regions in the Middle East and South America [1]. In contrast, many African and European countries do not fully benefit from the subsistent and commercial cultivation of soybean. The less significant role of soybean in these regions may be due to the poor growth conditions. The growth and productivity of this crop has been adversely affected by the biotic and abiotic stress factors [2]. Even though it has the potential to become a major crop in less cultivated regions (Africa and Europe) because of its many uses (as feed, food, etc.), plant modifications to increase yields are highly required [3].

**2. Importance of soybean**

Soybean plays a critical role in world agriculture, providing about 40% proteins, 20% oil and 30% carbohydrates contained within the seeds. This crop serves as the cheapest and profitable form of oilseed worldwide for many producers, especially small holder poultry farmers [5]. The industrial processing of this crop to manufacture high protein rich feeds for livestock, pigs and fish farms is growing immensely. The use of soybean in the production of edible oil and biodiesel as a green alternative fuel is also expanding [6]. In human nutrition and health, soybean meals have proved to reduce the cause of several acute and chronic conditions. Messina [1] reported the improvement of body calcium retention lowering urinary calcium excretion after the use of soy-proteins compared to consumption of a mixture of animal proteins. **Table 1** provides information regarding the estimated amount of seed yields used for industrial processing, meal manufacturing and some of the pharmaceutical products derived from soybeans. Following the drought because of El Nino-related conditions in the sub-Saharan Africa, soybean yield prospects for 2017/2018 have deteriorated, including productions in South America and Southeast Asia. The lowering projections will influence manufacturing and processing of soybean products for many industries and human consumption. Soybeans were also found to contain low fats (approximately 5%), easily modulated trypsin inhibitors and other compounds considered as non-nutritive components. Some of these compounds like phytate were considered to reduce mineral bioavailability of beans but, it has been postulated that phytic acid also lowers the risk of colon and breast cancer [7]. Soybean is considered an excellent source of iron, zinc and folate which serve as essential nutrients and reduce the risk of neural

The Role of Plant Genotype, Culture Medium and *Agrobacterium* on Soybean Plantlets…

http://dx.doi.org/10.5772/intechopen.78773

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tube defects in humans and promote efficient uptake of vitamin C [8, 9].

**Table 1.** Soybean producing areas, yield estimates and consumption/processing on industrial scale.

Among all the legumes, soybeans are unique because they are a concentrated source of isoflavones that naturally reduce the risk of cancer and heart disease [1]. In addition, soybeans also contain cysteine proteases protein enzymes. These are one of the group of proteolytic enzymes that catalyse the hydrolysis of various polypeptide substrates for the production

The genetic modification techniques such as the *Agrobacterium*-mediated genetic transformation, electro and chemical cell surface poration or direct protoplast-mediated DNA transfer need to be used to improve the agro-economic traits of this crop in those regions. *Agrobacterium tumefaciens* is a gram-negative soil borne bacterium, which infect dicotyledonous plants, causing a crown gall disease. The crown gall tumour is formed around the wound sites, creating a reservoir for its infestation [4]. The procedure for plant transformation takes advantage of this natural infecting ability to transfer the tumour-inducing plasmid (Ti-plasmid) into hosts. The plasmid DNA is naturally found within the bacterium, and is exploited for transformation with foreign DNA segments of interest obtained from different sources. The genes of interest could be introduced into the host plant's genome during bacterial infection. This phenomenon is known as genetic transformation, whereby the Ti-plasmid expression and integration of the transfer DNA (cloned segment of DNA transferred into hosts) within the host plant genome can also be inherited by the offspring of the host [5].

The first tissue culture based *in vitro* genetic transformation using this approach was reported by Hinchee et al. [6]. Subsequently, numerous reports emerged including those of Chee et al. [7], Yan et al. [8], Shi-Yun [9], Olhoft et al. [10] and Homrich et al. [11] on the use of *A. tumefaciens* to introduce agro-economic traits such as the resistance to pests (*Bt* crops), enhanced protein quality and drought stress tolerance in soybean. This chapter provides a review on the factors affecting *Agrobacterium*-mediated transformation, and gives an account on the outcomes obtained during the valuation of factors that cause recalcitrance during genetic transformation of soybean. The study provides a thorough analysis of the organogenic and phenotypic responses that occur due to the tissue culture conditions and the amenability of genotypes to *Agrobacterium* infection. The application of antimicrobials, plant growth regulators, culture media, bacterial density and the type of explants used influence the transformation efficiency of soybean. Optimised routine strategies in the transformation of soybean are still a prerequisite, since this crop is highly considered recalcitrant.
