The development of a cell suspension culture system for the scaling up of coconut embryogenic callus (EC) production would drastically improve efforts to achieve the large-scale production of high-quality clonal plantlets. To date, the hard nature of coconut EC appeared to be the main constraint for developing cell suspension cultures. Hence, this study attempted to acquire friable EC through the following approaches: The manipulation of (1) medium type and subculture frequency, (2) a reduced 2,4-dichlorophenoxy acetic acid concentration during subculture, (3) the nitrate level and the ammonium-to-nitrate ratio, and the addition of amino acid mixture, (4) the addition of L-proline, and (5) the reduction of medium nutrients. Unfortunately, none of these culture conditions produced friable coconut EC. Even though friable EC was not achieved via these approaches, some of the conditions were found to influence the formation of compact EC, therefore these results are important for further studies focused on somatic embryogenesis in coconut and other species.

As one of the most important members of the palm family, coconut (Cocos nucifera L.) currently faces a substantial gap between demand and production. Current plantings of this crop are aging, and these traditional varieties are susceptible to several devastating pests and diseases. Consequently, there is an urgent need to replant and expand coconut lands with new, genetically superior varieties. Such replanting cannot be met through the conventional method of seed nut planting, and tissue culture has emerged as a likely solution to address this problem. However, due to certain technical barriers, elevated costs, and a need for improved efficiency, the development of automated and highly efficient tissue culture techniques is yet to be developed. The present research explores the potential of an in vitro temporary immersion system (TIS) to improve the production of somatic embryogenic callus for plantlet regeneration. Results indicated that, in comparison to the conventional agar-based method used to produce coconut somatic embryogenic callus, the TIS method significantly enhanced embryogenic callus production. The optimal biomass of callus for inoculating the TIS was determined to be 0.2 g in each 900 mL vessel and the most favorable embryogenic developmental stage for employing TIS was the globular stage of embryo development. The most effective immersion time to give the highest yield of embryogenic callus was 5 min every 6 h. This foundational research demonstrates that a TIS step is likely to be important to rapidly produce, on a large scale, coconut plantlets to meet the escalating demand for materials for the replanting of coconut lands.

The coconut (Cocos nucifera L.), a valuable tropical crop, is rapidly declining in genetic diversity due to natural disasters, pest and disease attack, and land clearing for other crops. Seed banking is impractical for coconut conservation due to its large, recalcitrant seed, and maintaining field gene bank collections is costly and vulnerable to environmental pressures. Cryopreservation offers a promising alternative method for conserving coconut genetic diversity, but the success in recovering cryopreserved materials remains limited, with few studies consistently reporting high rates of recovery. This highlights the need for improved cryopreservation protocols, particularly in tissue dehydration, which is one of the critical steps in the process of cryopreservation and plant recovery. A desiccator was developed that enabled rapid embryo dehydration with ultra-dry airflow. The desiccator reduced embryo moisture content to 20% (the predetermined viability threshold) within 6 h representing a 2-h improvement when compared to a previous dehydration approach, while maintaining a high germination rate (71%). Smaller embryos (500 to 550 mg fresh weight) desiccated faster than larger embryos (800 to 900 mg fresh weight) but germination was reduced (30%), making small embryos unsuitable for cryopreservation. A 5-day sucrose (0.4 M) pre-treatment further reduced the dehydration time to 4 h, while maintaining a high germination rate (70%). These advances in the use of a sucrose pre-treatment, the rapid embryo dehydration, and selection of large embryos size will help to enhance the success of coconut embryo cryopreservation and recovery.