Progress and Prospects for Agrobacterium-Mediated Genetic Transformation in Sorghum in Comparison to Other Cereals

Abstract

Transgenic technology in sorghum, Sorghum bicolor L. (Moench), especially the Agrobacterium-mediated method, has picked up momentum in the recent past. High throughput Agrobacterium-mediated transformation in sorghum is prerequisite for use as a tool in functional genomics through T-DNA insertional mutagenesis and for development of marketable transgenic crop products. Despite equivalent efficiency in transient expression with other cereals, recovery of transgenic plants in sorghum is quite low, which can be attrib-uted to a loss of regeneration potential over subsequent prolonged subculture and treatment with agents for decontamination of Agrobac-terium. It can be overcome by right-choice of starting material with high regeneration and effective in vitro culture methods. Immature inflorescences are resourceful for high regeneration in sorghum, but recovery of plants subsequent to Agrobacterium-based methodology is very low. In vitro methods based on seed as the starting material in sorghum stand inefficient. Alternatively, immature embryos are frequently used explants for genetic transformation and these protocols need further improvement for increasing the efficiency of transformation in sorghum. Thus, the critical factors in Agrobacterium-mediated genetic transformation in sorghum include (i) moderation of Agrobacterium-infection parameters (ii) decontamination procedures with least phytotoxic effects (iii) efficient plant regeneration and (iv) specialized vectors for high efficiency transformation. The current review presents the achievements in Agrobacterium–based genetic transformation of sorghum and possible recommendations in the light of developments in other cereals.