In vitro culture Cynara cardunculus var. sylvestris – callogenesis induction and micropropagation

Abstract

Cynara cardunculus L., a cross-pollinated species complex, has a high level of heterozygosity, giving rise to different phenotypes within populations when propagated by seed. Traditional vegetative propagation of cardoon by offshoot involves the destruction of the mother plant, dissemination of phytosanitary problems, and a low multiplication rate due to the limited number of offshoots produced by the mother plant. Micropropagation is a viable alternative method for large-scale production of selected disease-free plants. The main goal of this work was the study of two in vitro propagation methodologies, micropropagation by shoot tips and callogenesis induction, aiming to multiply disease-free plants of selected Portuguese genotypes. Leaves and offshoots of different genotypes were submitted to two disinfection protocols. For micropropagation from field offshoots, the MS medium combined with IBA and BAP was used, while for callogenesis from leaves, seven combinations of growth regulators (NAA, BAP, IBA, KIN) were studied. The disinfection procedure was important to minimize the contamination rates during the culture establishment phase by shoot tips. The explants overcoming this phase were then multiplicated and rooted. For callogenesis induction, a new protocol of cardoon genotypes was developed for further indirect organogenesis and secondary metabolites production. A higher callus formation was obtained in BAP:NAA (1:10 mg L -1 ) or BAP:NAA (1:2 mg L ) media. The type of leaves (young versus adult) seems to be determinant in callus initiation, considering a lower level of contamination obtained with young leaves. For callogenesis and micropropagation by shoot tips, the genotype type influenced the callus formation and induction stage of shoots, respectively. This study represents the first investigation into the in vitro propagation of Portuguese cardoon genotypes. Further studies are being conducted to increase the induction and rooting rates to implement this new knowledge in future cardoon breeding programs.