Key message A standard method has been developed
with which we are able to fully regenerate protoplasts of
different Cichorium species. For the first time, endive
protoplasts have been regenerated into plantlets.
Abstract Protoplast regeneration is essential for somatic
hybridizations. In this study, a standard method for plantlet
regeneration from Cichorium protoplasts was developed.
We evaluated the effect of the low melting point agarose
(LMPA) bead technique on the regeneration capacity of
protoplasts of seven C. intybus and four C. endivia genotypes.
The LMPA bead technique was more efficient than
culture in liquid or solid medium and allowed us to obtain
plating efficiencies up to 4.9 % in C. intybus genotypes and
efficiencies of up to 0.7 % in C. endivia genotypes.
Moreover, the LMPA bead technique offers great advantages
over liquid and solid culture systems: the media can
be readily refreshed, protoplasts can be monitored separately,
and microcalli can easily be removed from the
beads. This increased efficiency was observed for all of the
11 Cichorium genotypes tested. Shoot formation was
induced more efficiently when using 0.5 mg l-1 indole-
3-acetic acid-enriched medium (up to 87.5 % of the protoplast-derived calli started shoot development) compared
to 1-naphthaleneacetic acid-enriched medium. The
LMPA bead technique optimized in this study enabled for
the first time the full plantlet regeneration from protoplasts
of C. endivia genotypes and increased the protoplast
regenerating ability in other Cichorium species. This finetuned
LMPA bead technique can therefore be applied for
protoplast regeneration after protoplast fusions of the genus
Cichorium.