# Somatic Embryogenesis of Selected Pinus Species: Developmental Stages of Pinus peuce and Pinus heldreichii

## TL;DR

This paper reviews the somatic embryogenesis process in two pine species, highlighting the challenges and key factors for successful clonal propagation.

## Contribution

The study provides species-specific insights into the developmental stages and conditions for somatic embryogenesis in Pinus peuce and Pinus heldreichii.

## Key findings

- Embryogenic tissue formation in Pinus species is highly dependent on the explant type and developmental stage.
- Successful SE in Pinus heldreichii requires reduced ammonium concentration in the medium.
- A narrow developmental window (4–10 weeks post-fertilization) is critical for SE induction in these species.

## Abstract

Somatic embryogenesis (SE) represents the most efficient and scalable technology for the mass clonal propagation and genetic improvement of superior conifer genotypes, which is crucial for meeting global wood demand and supporting forest adaptation to climate change. Despite its immense potential, SE in the genus Pinus still faces major limitations, including low initiation frequencies, restricted explant availability, and pronounced genotype dependence. This review synthesizes current knowledge on the factors influencing SE in Pinus species, with a specific focus on two ecologically vital Tertiary relicts endemic to the Balkan Peninsula: Pinus peuce (Macedonian pine) and Pinus heldreichii (Bosnian pine). For these species, traditional vegetative propagation methods are difficult or ineffective, making SE the priority approach for clonal propagation. Detailed studies on these species revealed that SE induction is highly dependent on the explant type and developmental stage. Successful embryogenic tissue formation was achieved only from whole megagametophytes containing immature zygotic embryos, within a narrow developmental window spanning 4–10 weeks post-fertilization. Furthermore, medium composition, particularly reduced ammonium concentration, proved critical for P. heldreichii success. These findings underscore the need for continued, species-specific optimization to overcome current bottlenecks and realize the full potential of SE for the conservation and sustainable clonal forestry of these high-value pines.