Among the four selective agents examined, kanamycin had no effects on callus growth at
all concentrations tested. Whereas G418, hygromycin and bialaphos inhibited callus
growth to various extents; callus browning was observed on media containing 75 mg l1
of G418, 25 mg l1 or more of hygromycin, or 1 mg l1 or more of bialaphos; and callus
growth was completely inhibited and the calli showed necrosis on media containing
50 mg l1 or more of hygromycin, or 4 mg l1 of bialaphos. On the other hand, both
antibiotics for eliminating Agrobacterium, cefotaxime and carbenicillin, significantly
promoted callus growth at all concentrations tested.