Effective hygromycin concentration for selection of transformed embryogenic calli of cassava variety H-226

Cassava is a starchy root crop used for food, feed, and industrial purposes. Antibiotic resistance genes are used as a marker for selecting transformed cells from non-transformed cells in genetic engineering. The optimum concentration of selective antibiotics is crucial for transforming and regenerating transformed plants. The current study aims to determine the optimal cytotoxic concentration of hygromycin for screening both transformed and non-transformed calli. The embryogenic calli were subjected to particle bombardment using the binary vector pCAMBIA 1305.1, which included the GUS reporter gene and the hptII gene. Hygromycin was added to the callus induction and regeneration medium at 0, 25, 50, 75, and 100 mg L-1 concentrations to identify the optimal selective concentration. Results indicated that 50 mg L-1 of hygromycin inhibited non-transformed calli and maintained the health of transformed calli. This concentration provided sufficient selective pressure with minimal cytotoxic effects, thus serving as the optimal level for distinguishing transformed cells in the cassava genetic transformation system.