Somatic Embryogenesis of Coffea liberica New Clone in Malaysia

Abstract

There has been a recent increase in the need for planting materials for Coffea liberica. In this study, we induced somatic embryogenesis of C. liberica leaf explants on modified Murashige and Skoog (MS) medium supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D), thidiazuron (TDZ), and 6-benzylaminopurine (BAP). The explants developed embryogenic calluses after 6 weeks of culture in MS medium supplemented with 0 mg/L BAP, 1 mg/L BAP, and 1 mg/L BAP + 1 mg/L TDZ. However, the explants cultured on MS medium supplemented with 1 mg/L BAP + 0.5 mg/L 2,4-D and 1 mg/L TDZ + 0.5 mg/L 2,4-D demonstrated no callus formation and browning of the leaf disc. Moreover, after 26 weeks of culturing, most cultures across all treatments were compromised due to browning except those cultured in MS medium supplemented with 1 mg/L BAP. Of these, 25% of MKL 10 (previously known as 224) clones survived, while only 10% of the clones differentiated into somatic embryos after 40 weeks of culture. Cotyledonary embryos were transformed into fully developed plants after 60 weeks of culturing. These results indicate that somatic embryogenesis of C. liberica leaf explants occur exclusively on MS medium supplemented with 1 mg/L BAP. Additionally, our results suggest that MS media supplemented with 1 mg/L BAP and 1 mg/L BAP + 1 mg/L TDZ were optimal for the induction of MKL 8 and 10 somatic embryogenesis, respectively. Both MKL 8 and 10 clones produce somatic embryos through the indirect embryogenesis pathway, except for MKL 10, which generates somatic embryos through both direct and indirect paths.