Influence of gelling agents on in vitro shoot proliferation of globe artichoke [Cynara cardunculus subsp. scolymus (L.) Hegi] genotypes

Propagation by meristems represents the only way to obtain disease-free artichoke plantlets but furthereffort is still necessary to optimize the in vitro technique for the different genotypes. Furthermore, genotypicdifferences play an important role in the response of this species to in vitro culture. In the present work, theeffects of five gelling agents (three different agar brands, gellan gum and agarose) on secondary shoot formationand development were investigated in one late (‘Romanesco C3’) and two early genotypes (‘Violetto di Sicilia’and ‘Violetto di Provenza’) of globe artichoke. The gelling agents notably affected the proliferation rate in thelate variety, but also in the two early ones, which are the most difficult to micropropagate. The highest numberof normally developed shoots was observed on Lickson bacto agar (5.6 shoots per explant) and agar agar (5.0shoots per explant). Even if low sodium content seems to be an essential prerequisite for gelling agents, greaterwater availability and the occurrence of relevant quantities of Ca and Mg ions, which may counteract sodiumeffects, may also play an important role, as evidenced by the good performances of the two best agar brands. Furthertrials may assess the opportunity to enhance the level of these elements in the medium in order to use thebest performing gelling agents.