MINIMAL INHIBITORY CONCENTRATION OF HYGROMYCIN FOR SELECTING TRANSFORMED OIL PALM EMBRYOGENIC CALLI

Determination of optimum concentrations for a selection agent is important in obtaining true transformants during the selection stage. In this study, the minimal inhibitory concentrations of hygromycin for four different types of oil palm embryogenic calli (suspension, fine, yellowish and whitish) that were cultured on proliferation, maturation and regeneration media were assessed. The embryogenic calli were cultured on media supplemented with different concentrations of hygromycin. Data on embryogenic callus weight increment was recorded monthly for six months during subculturing. Our results demonstrated that oil palm embryogenic calli cultured on regeneration media (EC) were very sensitive to hygromycin. The growth of embryogenic calli was affected at a relatively low concentration of hygromycin as compared to suspension calli that were cultured on proliferation media (L-1). The regeneration of fine, yellowish and whitish embryogenic calli was completely inhibited at 5-6 mg litre-1 of hygromycin. In contrast, higher concentration of hygromycin at 10 mg litre-1 is needed to inhibit the proliferation of suspension calli cultured on proliferation media. The hygromycin concentrations determined for each of the embryogenic callus types can be used as a guideline to select true transformants in future oil palm transformation works.