Coconut [Cocos nucifera L.] is often called “the tree of life” because of its many uses in the food, beverage, medicinal, and cosmetic industries. Currently, more than 50% of the palms grown throughout the world are senile and need to be replanted immediately to ensure production levels meet the present and increasing demand for coconut products. Mass replanting will not be possible using traditional propagation methods from seed. Recent studies have indicated that in vitro cloning via somatic embryogenesis is the most promising alternative for the large-scale production of new coconut palms. This paper provides a review on the status and prospects for the application of somatic embryogenesis to mass clonal propagation of coconut.

The NAC (NAM, ATAF1/2, CUC2) transcription factors are widely known for their various functions in plant development and stress tolerance. Previous studies have demonstrated that genetic engineering can be applied to enhance drought tolerance via overexpression/ectopic expression of NAC genes. In the present study, the dehydration- and drought-inducible GmNAC109 from Glycine max was ectopically expressed in Arabidopsis (GmNAC109-EX) plants to study its biological functions in mediating plant adaptation to water deficit conditions. Results revealed an improved drought tolerance in the transgenic plants, which displayed greater recovery rates by 20% to 54% than did the wild-type plants. In support of this finding, GmNAC109-EX plants exhibited lower water loss rates and decreased endogenous hydrogen peroxide production in leaf tissues under drought, as well as higher sensitivity to exogenous abscisic acid (ABA) treatment at germination and early seedling development stages. In addition, analyses of antioxidant enzymes indicated that GmNAC109-EX plants possessed stronger activities of superoxide dismutase and catalase under drought stress. These results together demonstrated that GmNAC109 acts as a positive transcriptional regulator in the ABA-signaling pathway, enabling plants to cope with adverse water deficit conditions.

Palms (Arecaceae) contribute remarkable economic and environmental values to human life. However, many elite and commercial palm species are becoming critically endangered and demand immediate action to preserve their genetic resources. Cryopreservation has established itself as the definitive in vitro conservation method for recalcitrant-seeded species, such as those within the Arecaceae. Progress in this area has moved steadily forward over the last three decades with the development of various techniques for different explants and palm genotypes and for molecular testing methods to ensure genetic fidelity is maintained in the regenerants. There remains a key challenge to properly identify the components that will enable the long-term conservation of palms using cryopreservation. This review methodically analyzes the state-of-the-art cryopreservation techniques developed for palms and places them within a practical framework. This framework encompasses four underlying components, namely the tissue culture approaches required, the recalcitrant nature of the palm seed, the cryobiology and cryogenic techniques required, and fidelity assessment after cryopreservation. Through a critical analysis of this framework, further optimization of palm cryopreservation protocols and more fundamental studies on the physiological and molecular changes in cryopreserved palm tissues are recommended. The present review helps to showcase a multi-decade global attempt to preserve these mostly recalcitrant species through ex situ collections. From a conservationist’s perspective, this review hopes to stimulate awareness for further concerted efforts in the conservation of rare and endangered plant families. Meanwhile, from a managerial perspective, this work serves to inform decision-makers of the global research effort underway to improve key components of the cryopreservation program for palm species and to encourage funding bodies to appropriately allocate resources to these much-needed research areas.