Initiation of Direct Shoot Organogenesis in Coconut Using Immature Inflorescence

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.