The commercialization of GM technologies for staple food crops such as wheat has faced the obstacles of social and market opposition and resistance.313 Fortunately (or fortuitously), gene transformation techniques for improving wheat yield have been challenging for plant biotechnology: bread wheat (Triticum aestivum L.) has one of the largest and most complex plant polyploid genomes, 80% of which consists of non­coding sequences, deriving from three ancestral genomes; new initiatives to analyze the minority expressed portion of the wheat genome are ongoing, but the structural complexity of the genome has been of enormous value to agronomy over millennia because major chromosomal rearrangements and deletions are well tolerated.314

Public perceptions may be more favorable to GM technologies applied to dedi­cated energy crops, although even here the fear is that of the introduction and spread of unwanted genes into natural populations with consequences that are difficult to accurately predict. Geographical isolation of energy crops (as of GM plants designed to synthesize high-value biopharmaceuticals) is one extreme solution but flies in the face of the limited land availability for nonfood crops. Even if the entire U. S. corn and soybean crops were to be devoted to bioethanol and biodiesel production (with complete elimination of all direct and indirect food uses), only 5.3% of the 2005 gasoline and diesel requirement could be met.315 Expressed another way, an area of land nearly 20-fold larger than that presently used for corn and soybean cultivation would be required for bioethanol and biodiesel energy crops. Concerns relating to land delineation are highly probable even if a wheat straw/corn stover bioeconomy is used as the main supply of feedstocks for bioethanol production.316

Equally inevitable, however, is that GM approaches will be applied to either dual food-energy crops or to dedicated energy crops such as fast-growing willow and switchgrass. The USDA-ARS Western Regional Research Center, Albany, Califor­nia, has created a gene inventory of nearly 8,000 gene clusters in switchgrass, 79% of which are similar to known protein or nucleotide sequences.317 A plasmid system has also been developed for the transformation of switchgrass with a herbicide resistance gene.318 Grasses share coding sequences of many of their genes: the sugarcane genome shows an 81.5% matching frequency with the rice genome and even a 70.5% matching frequency with the genome of the “lower” plant, Arabidopsis thaliana.319 The risk of gene transfer across species and genera in the plant kingdom is, therefore, very real.

A selection of patents relevant to transgenic crops and other plant genetic manip­ulations for bioethanol production is given in table 4.5.