Wheat (Triticum aestivum L.) is one of the world's most important crops with an annual production exceeding 570 million metric tons( FAO 2003). It is one of the most abundant sources of energy and proteins for mankind. Hence, wheat is a primary target for improvement of agronomic characteristics via biotechnology and genetic engineering (Lazzeri et al. 1997). However, the transgenic wheat plants were not obtained until 1992. Vasil et al. (1992) reported the first successful wheat transformation with a selectable marker gene bar and a reporter gene GUS by particle bombardment. Over the last 10 years, wheat genetic transformations via particle bombardment were widely applied for improving its end-used quality and resistance to abiotic/biotic stresses (Altpeter et al. 1996; Blechl and Anderson 1996; Barro et al. 1997; Bedo et al. 1998; Chen et al. 1998; Leckband and Lörz 1998; McIntosh 1998; Vasil et al. 1998; Rasco-Gaunt et al. 1999).

The widespread application of this method is still limited by relatively low and erratic stable transformation efficiencies. The efficiency of stable transformation is strongly dependent on wheat tissue culture and transformation procedures (Alpeter at al. 1996; Hess and Carman 1998; Iser et al. 1999; Rasco-Gaunt et al. 1999, 2001). A few agronomically less desirable model genotypes with good response in tissue culture and transformation, such as Bobwhite and Florida, were generally used in wheat transformation (Rasco-Gaunt et al. 2001). The application of this technology directly to elite wheat cultivars is preferable for the breeding programs, while it is not always possible due to the variability in regeneration and frequency rates of transformation between varieties User et al. 1999). Thus, it is essential to investigate the transformation frequencies among elite wheat varieties, and to optimize the procedures for their genetic transformation. The variations of transformation frequency among European and Japanese elite wheat verities had been evaluated (Takumi and Shimada 1997; Iser at al. 1999), and the particle bombardment parameters and procedures for European elite wheat verities had been reported (Rasco-Gaunt et al. 1999, 2001).

In China, wheat, rice and corn are the most important cereal crops. Many elite spring wheat cultivars have been widely used in the southern China. Till date, the informations about the transformation of Chinese elite spring wheat cultivars are not available. The objective of this paper is to optimize the tissue culture procedures of particle bombardment transformation for Chinese elite spring wheat cultivars.