1. Introduction
Sorghum [Sorghum bicolor (L.) Moench] is the fifth most important
crop among cereals in the world. It has advantageous adaptation to
semi-arid climate, such as higher water-use efficiency than maize
(Farre and Faci, 2006). However, sorghum tissue culture leading to
regeneration of transgenic plants has been limited by accumulation of
phenolics, low regeneration rate and short duration of regenerability
exhibited by callus cultures (Elhag and Butler, 1992; Jeoung et al.,
2002; Raghuwanshi and Birch, 2010).
Anumberof reportedmodifications have added incremental advances
in sorghum tissue culture system. For example, high concentrations of asparagine
and proline in culture induction media increase the proliferation
of sorghum embryogenic callus and diminish the production of toxic pigments
(Elkonin et al., 1995). Nitrogen and phosphorus molecular forms