Oil Palm Germplasm Resources and Their Conservation: Advances and Challenges for In Vitro Conservation.

In vitro germplasm conservation provides an alternative method for preserving plant species that are vulnerable to natural hazards or for which in situ conservation is costly and challenging to manage. This review examines the significance and challenges associated with various in vitro conservation methods. It also provides an overview of the current advances in cryopreservation technology for oil palm. In vitro conservation approaches include two strategies: medium-term conservation, in which plants are maintained through the slow growth of explants, facilitated by the gradual release of nutrients, and low-temperature storage. The second approach involves long-term preservation via cryopreservation in liquid nitrogen. Cryopreservation enables the storage of pollen, calli, somatic embryos, and zygotic embryos. Significant progress has been made in cryopreservation, which was initially limited to cold-tolerant species. New techniques focus on conserving sensitive species, such as oil palm, through rapid dehydration and vitrification procedures using various plant materials, particularly polyembryoids and zygotic embryos. Additionally, hardening of plant material is to be induced through pre-culture techniques to enhance their survival under osmotic stress and ultralow temperature. The mechanisms underlying the adaptability of various plant materials, i.e., somatic embryoids and zygotic embryos under cryopreservation, need to be understood.