Agrobacterium-mediated transformation of
indica rice has been established in only a limited number of
cultivars because the regeneration of plants from trans-
formed embryogenic calli is highly cultivar-specific.
Establishment of a highly efficient plant regeneration sys-
tem from shoot apex explants applicable to many cultivars
of indica rice will accelerate the application of transfor-
mation technology in breeding programs and functional
genomics study. We established an efficient shoot multi-
plication and plant regeneration system from shoot apices
of indica rice using thidiazuron (TDZ) as a plant growth
regulator. Shoot apices cultured on MS basal medium
devoid of plant growth regulators formed solitary shoots in
90% of cultures. Addition of TDZ or benzylaminopurine to
regeneration medium significantly influenced formation of
multiple shoots directly from shoot apex explants without
an intervening callus stage. Best shoot proliferation
response (10.3 shoots per explant) was recorded when
shoot apices were cultured on media supplemented with
4 mg/l TDZ. No synergistic effect on shoot proliferation
was observed when indole-3-acetic acid and indole-3-
butyric acid were supplemented to media containing 4 mg/l
TDZ. The regeneration system was efficient in evoking
multiple shoot proliferation in eight different cultivars of
indica rice. Shoots were rooted in MS basal medium and
plantlets were acclimatized with 100% survival rate. The
shoot apex explants of all the eight cultivars of indica rice
were found competent to Agrobacterium-mediated trans-
formation while explants from IR-64 showed highest
transient GUS expression. This variety-independent trans-
formation amenable regeneration system from shoot apices
may widely be applicable for genetic transformation of
indica varieties.