Influence of 2,4-D Growth Regulator and Foliar Explant Source on Coffea arabica Embryogenic Calli

Aims: With the goal of obtaining Coffea arabica varieties with greater productivity and resistance, researchers in Brazil have been conducting experiments on elite plant propagation through in vitrotechniques, such as somatic embryogenesis. This large-scale multiplication method has great potential for exploration and could enable maximization of coffee propagation. The aim of the current work was to compare the effects of different 2,4-D concentrations and two pre-established methodologies for obtaining embryogenic calli of Coffea arabica, and to evaluate whether the foliar explant source can affect somatic embryogenesis.

Place and Duration of Study: The experiments were conducted in the Central Laboratory of Molecular Biology at the Federal University of Lavras, (Brazil), between 2016 and 2017.

Methodology: The calli of Coffea arabica cv. Catiguá MG2 were obtained using two well-known methodologies and from two explant sources: seedling leaves cultivated both in vitro and in a greenhouse. The quality of potentially embryogenic calli was verified by morphological analysis by light microscopy, and the quantity was determined by analysis of variance.

Results: After five months of culture, all treatments generated potentially embryogenic calli. The calli were histologically characterized as having a homogeneous tissue consisting of small isodiametric cells and aggregates displaying a dense cytoplasm and clear nuclei. Numerous small starch grains were also noted.

Conclusion: The plant leaf explants grown in vitro showed a high percentage of potentially embryogenic calli after inoculation in a culture medium containing a low 2,4-D concentration. Morphological characteristics may therefore be used as structural markers to select embryogenic cultures.