Some Studies on Callus Induction and Growth in Sorghum

The ultimate goal of this work is to end with plants carrying stress tolerance gene(s) in homozygous state.This could be achieved by subjection of haploid cells grown in culture to the sought stress, doubling the chromosomes of the surviving cells, growing those cells into callus masses and finally differentiating the callus masses into buds which can be grown to mature plants. Success of this technique would save up to 80 % of the time usually spent to reach homozygosity by the conventional breeding methods. To reach this ultimate goal we have to establish a stable pathway by going through the following experimental steps: Induction and growth, within a reasonable period of time, of a flow of sufficient amounts of sorghum callus, in vitro, to satisfy the experimental needs. Separation of the callus cells from each other and growing them as free cells in liquid medium. Subjection of the free cells to whatever treatment is necessary to screen for the stress tolerance. Treating the surviving cells with colchicine to double their chromosomes. Transferring these cells to a solidified medium and promoting their division in order for them to grow into callus masses. Subjecting those callus masses to the proper treatment for them to differentiate into buds, which can eventually be grown into mature plants. Most attempts to culture tissue from monocotyledonous plants were less successful than attempts of culturing comparable tissue from dicotyledonous plants.The only paper found which was concerned with sorghum tissue culture was that of Masteller and Holden (1970).The sorghum callus cultured by their method was slow, variable and, in most instances, produced a pigment which turned both the callus and the medium black. The objective of this research was to study the possibilities of routine induction and growth of pigment-free sorghum callus tissue in vitro. The ability to obtain a routine continuous flow of sorghum callus is the first major step toward developing a technique for obtaining stress tolerant genetic material. Advisor: Max D. Cleg