Table 1. Comparison of transformation achievements in rice and wheat crops: Milestones in terms of efficiency and realizations.

Efficiency of transformation technology from initial development to successful outcome
Rice		Wheat
Shortly after the development of transformation technology, efficiency (22%) was reported to be as high as that reported in dicots 21, 108-110. Although there are some varietal differences, yields increased by several hundred percent 24, 33, 111-113.		Since the pioneering work in this area, there has been significant progress in the methodology, but it is still confined mainly to a few responsive varieties, with efficiency ranging from less that 1% to 10%; high throughput transformation channels, such those developed for rice, are not yet available 22-25, 114, 115.
Functional genomics About 10,000 and 100,000 independent lines were generated for large-scale applications, such as T-DNA insertion mutagenesis and functional genomics, respectively 26, 27. RNAi silencing The first commercial improved cultivar produced by RNAi technology sought to reduce the level of undesirable metabolites to a value not yet achieved using conventional methods. The low glutenin content rice variety was useful for patients with kidney disease whose protein intake is restricted and who are unable to digest glutenin 28, 29. Gene targeting (GT) and genome editing A high-throughput Agrobacterium-mediated transformation model was essential for the development of GT in rice and has opened the door to the development of this technology for crop plants31-33 . Some 12,000 FOX (Full-length cDNA Over-eXpresser) lines were generated for analyzing gain-of-function phenotypes from large populations of transgenic plants overexpressing cDNAs of interest and others with unknown functions in rice30 .		Functional genomics For crops where gene transfer efficiency and subsequent plant regeneration remain a limitation, a nontransgenic method for reverse genetics, called TILLING (Targeting Induced Local Lesions IN Genomes) has been developed. TILLING has been extended to the improvement of crops such as wheat and is seen as a useful general method for both functional genomics and the modulation of key traits116 . For functional genomics projects, it has been suggested that barley be used as a model for wheat due to its highly efficient transformation rates and smaller, less complex genome22 . RNAi silencing Several wheat studies aimed at improving human health through its resistant starch content or allergens have been conducted. High-amylose lines were generated using RNAi via downregulation of the two different isoforms of starch-branching enzyme, SBEIIa and SBEIIb. Improved indices of large-bowel health were demonstrated in rats28, 117. Reduced gliadin (gluten proteins associated with the development of celiac disease) was obtained in the ‘Bobwhite’ model cultivar118. Gene targeting (GT) and genome editing GT of a particular genomic location has been shown to be applicable to regenerable hexaploid wheat cells119 , but further advances are required before it can be routinely used22.

¹FOX: This gene-hunting system is a transgenic procedure that uses a normalized full-length cDNA collection under the control of the constitutive CaMV35S promoter; it offers a technique for identifying new gain-of-function in phenotypes. TILLING: This is a nontransgenic method for reverse genetics that uses molecular biology and genomics to identify point mutations in selected gene(s) amplified from a mutagenized population, using high-throughput detection platforms such as slab gel electrophoresis, capillary electrophoresis or dHPLC