Contrasting Embryogenic Trajectories Reveal Spatial Control as a Key Determinant of Embryogenic Competence in Theobroma cacao L.

Abstract

ABSTRACT Somatic embryogenesis (SE) in Theobroma cacao is a micropropagation technique of great importance but remains constrained by genotype recalcitrance. The cellular and molecular mechanisms distinguishing regenerative from non‐regenerative responses remain poorly understood. Here, we elucidate the ontogenetic events governing embryogenic competence by comparing responsive genotypes (CCN‐51 and 752) with a recalcitrant one (PH16). Our results demonstrate that SE success in cacao is not determined by cell proliferation speed, but rather by a slow, organized, and spatially confined developmental trajectory. Through histological and immunofluorescence analyses, we show that responsive genotypes establish a focused response within procambial tissues. This leads to the formation of late, localized auxin maxima (after 42 days), which are essential for organizing morphogenesis. In contrast, the recalcitrant genotype exhibits a rapid, diffuse, and disorganized response that fails to establish necessary hormonal gradients, resulting in developmental collapse. We conclude that embryogenic competence in cacao should be redefined: it is not merely an induction event, but the precise orchestration of a developmental program dependent on the controlled reactivation of a vascular stem cell niche. These findings provide novel morphological and hormonal markers for selecting elite genotypes and offer new strategies to overcome recalcitrance in cacao.