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

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.