A rare case of spontaneous in vitro inflorescence formation during micropropagation of date palm Phoenix dactylifera L.

Abstract

Commercial micropropagation of date palm (Phoenix dactylifera L.) aims to maintain strict vegetative development to ensure clonal fidelity and high multiplication efficiency. The induction of reproductive structures under in vitro conditions is therefore considered undesirable and extremely rare. In this study, we report a well-documented case of premature inflorescence formation observed during hormone-free subculture in date palm cv. Khinazi. Among 3,658 culture jars maintained for a cumulative period of 471 days, only a single culture (0.027%) developed a floral structure. The anomalous culture originated from an offshoot collected during the fruiting stage and had been exposed to relatively high concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) during initiation. Furthermore, the culture was transferred directly from callus proliferation to hormone-free medium, bypassing the intermediate hormonal-reduction stage normally included in the protocol. We hypothesize that the combined effects of hormonal carryover, donor plant physiological status, and abrupt withdrawal of exogenous growth regulators may have triggered premature activation of reproductive developmental pathways. This observation highlights the developmental plasticity of date palm tissues under prolonged in vitro culture conditions and emphasizes the importance of controlled hormonal transitions and careful donor plant selection in commercial micropropagation systems.