Maize

Twenty years have elapsed from the first report of stable transformation of maize. Advances in various free DNA delivery methods and the more recent use of Agrobacterium tumefaciens in maize transformation has led to rapid strides towards increased effici

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Maize David D. Songstad

18.1

Introduction

Conventional plant breeding, molecular breeding and transgenic plant technology are coming together in a productive and meaningful way, allowing for rapid delivery of value added traits over the past 13 years. It is the synergy among these technologies that has allowed for the rapid advances in yield gain and introgression of novel traits into diverse germplasm much more rapidly than was possible in the recent past. Over these past 13 years, society has witnessed the introduction of herbicide resistant soybeans, starting in 1996 (Padgette et al. 1996) followed by the generation of other crops, notably herbicide-resistant cotton (Gossypium hirsutum; Chen et al. 2006), herbicide-resistant canola (Brassica napus; Stringham et al. 2003) and maize (Zea mays) resistant to European maize borer (Armstrong et al. 1995) and the herbicide glyphosate (Heck et al. 2005). The perennial growth in biotech acreage is testimony of the acceptance and benefits delivered to farmers. In 2007, 282 million acres (approx. 114 million ha) of biotech crops were planted world-wide resulting in US $7 billion of added economic benefit to farmers resulting from the biotech traits (James 2007). Maize is the premier monocotyledonous species for biotech research based on its positive tissue culture and transformation characteristics, conventional and molecular breeding advances and cash value in the agronomic marketplace. The advances in maize tissue culture and biotechnology have emerged from its infancy in the 1970s and 1980s to its current status where nearly 75% of the maize grown in the United States contains biotech traits (James 2007). The track record for maize biotechnology dates back to mid-1970s with the first documented regeneration of maize plants from callus cultures by Green and Phillips (1975). Approximately 15 years elapsed until the first reported regeneration of transgenic maize plants by

D.D. Songstad Monsanto C3N, 800 N. Lindbergh Boulevard, Saint Louis, MO 63167, USA e-mail: [email protected]

F. Kempken and C. Jung (eds.), Genetic Modification of Plants, Biotechnology in Agriculture and Forestry 64, DOI 10.1007/978-3-642-02391-0_18, # Springer-Verlag Berlin Heidelberg 2010

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Fromm et al. (1990) and Gordon-Kamm et al. (1990). More recently, Ishida et al. (1996) reported the first stable transformation of maize by Agrobacterium tumefaciens (see Chap. 1). This chapter focuses upon the advances which contributed to the current state of transgenic maize, the acceptance of biotech enhanced traits in the marketplace and the benefits delivered to the customer that include enhanced yield to help ensure our food security.

18.2

Culture Media and Supplements

A variety of basal media have been used to initiate maize callus cultures and regenerate plants. These include the MS (Murashige and Skoog 1962) formulation for indication of the first regenerable maize callus by Green and Phillips (1975). Since this time, plant regeneration as been reported from ca