Enhancing microshoot regeneration in "Turiaçu" pineapple through nodular cluster induction with putrescine.

• Putrescine enhances microshoot regeneration in Turiaçu pineapple. • Nodular cluster induction boosts propagation efficiency. • Morphoanatomical insights shed light on cluster development. • Nodule clusters offer a promising method for pineapple propagation. Nodular clusters are a morphogenetic pathway used in the in vitro propagation of Bromeliaceae due to their high responsiveness in the regeneration of microshoots. Additionally, endogenous polyamines, especially putrescine, may contribute to the induction of these nodular clusters. However, the potential effects of this regulator on the regeneration of microshoots when applied to explants are unclear, especially in traditional pineapple cultivars such as "Turiaçu". Therefore, our objective here was to induce and characterize the morphoanatomy of nodular clusters in combinations of 6-benzylaminopurine (BAP) and putrescine (PUT) in "Turiaçu" pineapple. Leaf segments induced in culture medium supplemented with 4 μM naphthaleneacetic acid (NAA), 8 μM BAP, and 100 μM PUT resulted in an induction rate of 56 %, with the formation of microshoots via nodular clusters, increased length, and the number of leaves per microshoot. Morphoanatomical studies revealed that in the medium with 4 μM NAA, 8 μM BAP, and 100 μM PUT, the clusters presented a voluminous size, microshoots with leaves, and the development of new leaves along the base of the explant, and the formation of meristemoids with small cells arranged in a spiral. The results indicate that auxins and cytokinins combined with exogenous putrescine are efficient for inducing nodule clusters. Thus, exogenous putrescine improves the efficiency of microshoot regeneration by nodular clusters. [ABSTRACT FROM AUTHOR]