Zhihua Mu

Coconut (Cocos nucifera L.) is one of the most widely cultivated crops, with increasing popularity and demand for its products, which necessitates increased production. However, the lack of high-quality planting materials is a major limitation in replanting the senile palms worldwide. This study examined the possibility of using a direct shoot organogenesis pathway as an alternative to somatic embryogenesis to produce clonal coconut plantlets using immature inflorescence explants obtained from Indonesia and Australia, through investigation of the explant types, exogenous plant growth regulators, and additives. Histological analysis showed suitable stages of immature inflorescence explants to be used, which led to the formation of shoot-like structures resembling true vegetative shoots, in all treatments consisting of exogenous plant growth regulators except for those without activated charcoal. The culture medium supplemented with thidiazuron (100 μM) alone or those supplemented with various combinations of other plant growth regulators showed similar shoot induction percentages (ca. 63 to 80%) or shoot-like structures per explant (ca. 6 to 8). The addition of adenine sulphate (217 μM) was found to significantly improve shoot induction (ca. 50%) from immature inflorescence explants compared to the control (ca. 5%), whereas phloroglucinol was found to negatively impact shoot induction, and L-glutamine showed a positive influence. The current study showed several improvements, which warrant further studies to develop commercial protocol for mass production of clonal coconut plantlets through direct organogenesis.

Coconut palm’s economic significance across the tropics, underpinning livelihoods and industries, is increasingly threatened by pests, diseases, genetic erosion, and natural disasters. This underscores the urgent need for efficient germplasm conservation strategies. In vitro culture of zygotic embryos provides a vital pathway for secure global conservation and exchange, particularly for elite varieties like Makapuno. However, standardized, practical protocols for the international exchange of fresh, non-cryopreserved embryos remain underdeveloped. To address this gap, this study refined a key protocol for fresh coconut embryo exchange by systematically optimizing critical parameters. The results demonstrated that an optimal culture medium containing low sucrose (10 g/L), activated charcoal (1 g/L), Gelrite (2.5 g/L), and 1 mL medium per cryotube significantly enhanced embryo size (40% increase; p < 0.05) compared to sucrose-free controls. While surface sterilization using AgNPs showed a marginal growth advantage over NaClO, rigorous transportation simulations confirmed that embryos retain high viability and regeneration potential only if delivered within seven days. These findings establish a robust, standardized framework for enhancing the global exchange and conservation of elite coconut germplasm, directly supporting genetic conservation and varietal improvement efforts.