Comparison of systems combining auxins with thidiazuron or kinetin supplemented with polyvinylpirrolidone during embryogenic callus induction in three <i>Theobroma cacao</i> L. genotypes

Abstract

For two decades, the combination 2,4-dichlorophenoxyacetic acid (2,4-D)/thidiazuron (TDZ) has been the most used to induce somatic embryogenesis in cocoa. The aim of this study was to compare the effect of combination systems, auxin/TDZ and auxin/kinetin (Kin) systems, as well as the addition of polyvinylpirrolidone (PVP) to these combinations on the induction of embryogenic calli in cocoa (Theobroma cacao L.). To this end, eight induction media combining auxin 2,4-dichlorophenoxyacetic acid (2,4-D) or 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) at 4,5 mM with cytokinin thidiazuron (TDZ) (22.8 nM) or kinetin (Kin) (1.125 mM) supplemented or not with PVP (300 mg / L) were evaluated on induction of embryogenic callus with petals or staminodes in three genotypes of cocoa. The basal salts medium was DKW (Driver and Kuniyuki Walnut medium). This study showed that the effect of 2,4-D combinations with Kinetin or TDZ was statistically identical on the induction of embryogenic callus. On the other hand, with 2,4,5-T, the association with Kin was more embryogenic than with TDZ. Furthermore, addition of PVP improved the induction of embryogenic callus in both combination systems. In the presence of PVP, media containing 2,4,5-T exhibited higher levels of embryogenic callus induction than their counterparts containing 2,4-D. This study allows the expansion of the possibilities of induction of embryogenic callus in cocoa.

Keywords: somatic embryogenesis, cocoa, petal, growth regulator, staminode, antioxidant.