Early morphogenesis of kopyor coconut (Cocos nucifera L.) embryos in vitro as affected by light conditions and thidiazuron concentration
¹Department of Agroecotechnology, Faculty of Agriculture, Universitas Sultan Ageng Tirtayasa, Serang, Banten Province, Indonesia
²Department of Agribusiness, Faculty of Agriculture, Universitas Sultan Ageng Tirtayasa, Serang, Banten Province, Indonesia
³Faculty of Plantation and Agrotechnology, Universiti Teknologi MARA, Malaysia
⁴Department of Environmental Studies, Universitas Sultan Ageng Tirtayasa, Serang, Banten Province, Indonesia
5Center of Excellent for Food Security, Universitas Sultan Ageng Tirtayasa, Serang, Banten Province, Indonesia
*Correspondence: susiyanti@untirta.ac.id
Abstract:
Kopyor coconut (Cocos nucifera L.) is a high-value coconut variant characterized by a naturally mutated endosperm; however, its propagation is constrained by low seed viability and inconsistent germination. In vitro culture offers a promising approach for large-scale propagation. This study evaluated the effects of light conditions and thidiazuron (TDZ) concentrations on the early morphogenesis of kopyor coconut embryos cultured in vitro. A split-plot design based on a completely randomized design was applied, with light conditions (dark and continuous light) as the main plot and TDZ concentrations (0, 0.25, 0.50, 0.75, and 1.00 mg L⁻¹) as subplots. The results showed that light conditions did not significantly affect explant height, shoot number and root number, or root length (p > 0.05), although plumule formation occurred exclusively under light conditions. In contrast, TDZ significantly influenced explant height (p < 0.01), while its effects on other parameters were not significant. The application of 0.25 mg L⁻¹ TDZ produced the most favorable response, with explant height reaching 3.00 ± 0.14 cmunder light and 2.60 ± 0.17 cmunder dark conditions, accompanied by 0.95 shoots and 0.86 roots per explant. No significant interaction between light conditions and TDZ was detected. These findings indicate that early morphogenesis of kopyor coconut embryos is primarily regulated by endogenous hormonal balance, with low TDZ concentrations optimizing growth responses, while light plays a critical role in organ differentiation, particularly in plumule formation. The results provide a basis for improving in vitro propagation protocols for this economically important coconut variant.
Key words:
Cocos nucifera L., in vitro, kopyor coconut, light conditions, morphogenesis, thidiazuron