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

Propagation by meristems represents the only way to obtain disease-free artichoke plantlets but further effort is still necessary to optimize the in vitro technique for the different genotypes. Furthermore, genotypic differences play an important role in the response of this species to in vitro culture. In the present work, the effects of five gelling agents (three different agar brands, gellan gum and agarose) on secondary shoot formation and 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 the late variety, but also in the two early ones, which are the most difficult to micropropagate. The highest number of normally developed shoots was observed on Lickson bacto agar (5.6 shoots per explant) and agar agar (5.0 shoots per explant). Even if low sodium content seems to be an essential prerequisite for gelling agents, greater water availability and the occurrence of relevant quantities of Ca and Mg ions, which may counteract sodium effects, may also play an important role, as evidenced by the good performances of the two best agar brands. Further trials may assess the opportunity to enhance the level of these elements in the medium in order to use the best performing gelling agents.