Micropropagation, Somatic Embryogenesis, and Haploid Induction in Passiflora: Advances, Biological Constraints, and Breeding Prospects

The genus Passiflora includes species important for fruit production, ornamental value, and breeding programs. Conventional methods, such as seed propagation and vegetative cuttings, face challenges like genetic heterogeneity, pathogen transmission, and long juvenile phases, limiting large-scale cultivation and breeding efficiency. In vitro culture technologies are essential for clonal propagation, germplasm conservation, and improving Passiflora species using biotechnology. This review critically evaluates current progress in micropropagation and regeneration systems in Passiflora spp. and examines the prospects of haploid and doubled haploid technologies as future breeding tools. Unlike previous reviews, which primarily focus on summarizing tissue culture protocols, this study integrates regeneration biology, developmental constraints, and emerging biotechnological approaches to provide a broader framework for research. Additionally, this review offers a comparative analysis of various regeneration systems across Passiflora species and highlights the challenges of genotype-dependent methods. By synthesizing recent advancements in haploid technology, it provides new insights into the potential for accelerating breeding programs in Passiflora, a field where robust protocols are still lacking.