LAUSR

Abstract Melocactus glaucescens is a cactus endemic to Brazil. In vitro shoot production represents a viable alternative to conventional propagation, since M. glaucescens grows slowly and requires about ten years to reach its reproductive phase. M. glaucescens can only reproduce by seed and does not ramify or emit lateral shoots. The present work evaluated the morphogenic potential of M. glaucescens by (i) using variations in explant fragmentation and orientation; (ii) the use of plant growth regulators (PGRs); (iii) and the occurrence of somaclonal variation. The results suggest that number of shoots decreased with greater explant fragmentation. Shoot induction can be achieved in culture media with or without PGRs. The evaluation of the morphogenic responses of M. glaucescens explants to PGRs revealed that, when combining naphthalene acetic acid (NAA) with benzylaminopurine (BAP) or kinetin (KIN), BAP yielded a greater number of shoots than KIN. However, with BAP concentrations of 4.44, 8.88, and 17.76 μM, shoots were morphologically different from the control plants. The ISSRs analysis showed polymorphisms in shoots produced with or without PGRs and suggests that other factors might affect the genetic stability of M. glaucescens. Our results indicate that M. glaucescens can be propagated using in vitro techniques with or without PGRs. Apical cladode segments can grow in PGR-free medium and can be used as a source of explants. The technique established in this work reduces the removal of seeds from natural populations, and therefore, does not interfere in the reproduction dynamics of this species in its natural habitat.