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 a further effort is still necessary to optimize in vitro technique for the different genotypes. In this species, in fact, genotypic differences play an important role in the response to in vitro culture. In this work, on a late ('Romanesco C3') and two early genotypes ('Violetto di Sicilia' and 'Violetto di Provenza') of globe artichoke, the effects of five gelling agents (three different agar brands, gellan gum and agarose) on secondary shoot formation and development were investigated.Gelling agents, indeed, notably affected the proliferation rate in the late but also in the two early varieties, the most difficult to micropropagate. The highest number of normal 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 seem to be an essential prerequisite of gelling agent, higher water availability and the occurrence of relevant quantities of Ca and Mg ions, which may counteract sodium effects, may play also an important role, as evidenced by the good performances of the two best agar brands. Further trials may assess the opportunity of enhancing the level of these elements in the medium in order to use the best performing gelling agents.