Embryogenic calli were induced from leaf
explants of coffee (Coffea canephora) on McCown’s
woody plant medium (WPM) supplemented with 5 mM
N6
–(2-isopentenyl)-adenosine (2-iP). These calli were
co-cultured with Agrobacterium tumefaciens EHA101
harboring pIG121-Hm, containing b-glucuronidase
(GUS), hygromycin phosphotransferase (HPT), and
neomycin phosphotransferase II genes. Selection of
putative transgenic callus was performed by gradual
increase in hygromycin concentration (5, 50, 100 mg/l).
The embryogenic calli surviving on medium containing
100 mg/l hygromycin showed a strong GUS-positive
reaction with X-Gluc solution. Somatic embryos were
formed from these putative transgenic calli and germinated
on WPM medium with 5 mM 2-iP. Regenerated
small plantlets with shoots and roots were transferred
to medium containing both 100 mg/l hygromycin and
100 mg/l kanamycin for final selection of transgenic
plants. The selected plantlets exhibited strong GUS
activity in leaves and roots as indicated by a deep blue
color. GUS and HPT genes were confirmed to be stably
integrated into the genome of the coffee plants by the
polymerase chain reaction.