Unlike rice embryogenic callus which can maintain regenerability
over 40 weeks (Nabors et al., 1983), sorghum embryogenic callus does
not maintain a useful level of regenerability over fourweeks. The reason
for this phenomenon is, as yet, unknown. Our data from three tested
lines unequivocally demonstrated that the optimal callus age was
two-weeks old. When callus was four-weeks old, the regeneration
rate and regenerability dropped markedly. For instance, SA281 could
produce 59 shoots per IE when callus was two-weeks old; however, it
only generated 3 shoots per IE when callus was four-weeks old
(Table 4). Therefore, callus age plays a critical role on regenerability