callus for infection

[Jones King <jonesking96@YAHOO.CA>]

Dear all,
I would like to get your advice about agro
transformation via callus.

1.Should I use initial callus or subcultured callus
for infection? If both, which would be better?

2.If initial callus is used for infection, should the
entire callus with the explant or pieces of callus be
used?

3.After co-cultivation, what selection medium would be
better, i.e. the same as callus induction or further
regeneration medium with antibiotics?

4. what are the visible signs of putative calli or
explants (if directly infect explants)as the selection
proceeding?

I am a beginner of agro transformation, so, many
simple but practical questions are hard to find out
from literature. Thank you.
jones