Sounds as if your in-vitro Solanum plants have a vascular wilt disease: a
bacterium (or fungus) that resides in the xylem and impedes fluid flow.
Some bacterial counts in Zea xylem can get so high that xylem exudate
actually becomes viscous with their cell fragments and secretions. Adding
antibiotic to the medium might ease the symptoms. Ask colleagues what theyt
use to purge cultures of Agrobacterium after transformation takes place.
Maybe the purging medium will already be made up for you in the lab.