A SIMPLE APPROACH TO ISOLATE SHOOT COMPETENT CELLS FROM SORGHUM [SORGHUM-BICOLOR (L) MOENCH] CALLUS-CULTURE

Stable shoots regeneration systems from somatic cells are crucial for genetic manipulation for cereal crops. The objective of this study is to establish a regeneration system by isolating the shoot competent cells from sorghum calluses [Sorghum bicolor (L.) Moench], and to evaluate the fertility and chromosomal variation of those regenerants. Callus derived from the immature embryos of sorghum containing heterogeneous cell types. Different cell types responded differently to the regeneration media by producing black pigments, regeneration of roots or shoots, or proliferation into embryogenic calluses. These differential responses were evaluated for their effectiveness in selecting the shoot regeneration competent cells. RSC 599 shoot competent cell clumps were easily identified and isolated from 2 mm(2) calluses placed onto the regeneration medium (SR). Calluses that had not differentiated with the milky white color were transferred to SC medium for proliferation and to SR2 medium for further regeneration. The calluses on SR2 medium produced somatic embryos on the surface and only multiple shoots have been regenerated from them. Ninety-eight percent regenerated plants were fertile, 90% with normal chromosome number and 10% of the plants were mixoploid with both 40 and 20 root-tip chromosome counts. From two 5 mm(2) selected cell clumps, hundred of shoots were regenerated. The strategy of isolating shoot competent cells through regeneration selection may provide a stable system for genetic manipulation in sorghum.