Phenol content, acidic peroxidase and IAA-oxidase during somatic embryogenesis in Theobroma cacao

Calli were induced in cacao cotyledon explants on a half-strength Murashige and Skoog medium containing 6x10*[-2] gm*[-3] saccharose and various combinations of 2,4-dichlorophenoxyacetic acid (2,4-D) with kinetin (kin), benzylaminopurine (BAP) or 2-isopentenylphosphate (2-iP). Experiments were carried out in two clones of cacao differing in their susceptibility to black pod disease. The highest percentage of explants forming callus and the most rapid callus development were obtained with 10*[-6] g m*[-3] 2,4-D and 0.5x10*[-6] g m*[-3] kin. Somatic embryogenesis and rhizogenesis were induced by transferring 3-week-old callus in a half strength Murashige and Skoog medium containing 3x10*[-2] g m*[-3] saccharose and NAA or IBA in the 0 to 5x10*[-6] g m*[-3] concentration range. No differentation could be observed when the medium was supplemented with kin or BAP. The conversion of callus into somatic embryos and roots was accompanied by a drop in phenol content and in increase in peroxidase and IAA-oxidase activities.