IN VITRO MORPHOGENESIS OF VENEZUELAN COCOA (Theobroma cacao L.) GENOTYPES
Rosalía Velásquez S.1*, Giovana Santana1, Ada Medina1, y Carmen Betancourt1
In order to induce in vitro regeneration of elite Venezuelan cocoa (Theobroma cacao L.) cultivars, floral explants were collected from ‘Collection 45’, in cocoa germplasm at the National Research Institute of Agriculture, Maracay, Venezuela. Three clones were selected: OC-61, OC-77 and CHO-42, using staminoids, petals and anthers. Culture media of Driver and Kuniyuki (DKW), and Lloyd and McCown (WPM) were used for callus development, supplemented with 2,4-Dichlorophenoxyacetic acid (2,4-D) (2 mg L-1) in combination with Thidiazuron (TDZ) (0.05 mg L-1), kinetin (Kin) (0.3 mg L-1) and N-6 benziladenine (BA) (0.05 mg L-1), which were used for callus induction (Driver and Kuniyuki), callus development (Mc Cown) and structure differentiation (Driver and Kunuyuki), respectively. Culture conditions were total darkness at 25 ± 2°C. When morphogenic differentiations of the structures were achieved, callus was transferred to 12 h light conditions. The highest percentage of callus formation was observed in CHO-42, when staminodes were used as explants. Differential morphogenic response related to color and callus consistencies were observed: compact white calluses, yellow creamy callus and brownish callus. According to histological observations, embryogenic cells only emerged from the latter type of callus, in clone CHO-42, which showed globular crystalline structures. Additionally, organogenic response was achieved in all genotypes but only in explants of anther and petals. However, the highest percentage of root formation was observed in anthers of CHO-42. According to the results obtained, the morphogenic response in cocoa is dependent on genotype and type of explant used.
Key words: cocoa, morphogenesis, in vitro, callus.
1 Instituto de Genética, Facultad de Agronomía, Universidad Central de Venezuela, Apartado postal 4579, Maracay 2101,Venezuela.
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