The effects of grafting on growth, development and some functional traits in cacao genotypes was examined. Treatments were six rootstock-scion combinations of three cacao genotypes: Amelonado (A), F3 Amazon (F) and TC2 Series (T). Genotypes Amelonado and F3 Amazon formed the rootstocks for the rootstock-scion combinations (AA, AF, AT, FF, FA, FT). Data were collected on the number of leaves at two week intervals for 24 weeks after grafting (WAG), stem girth (scion, graft union and below graft union girth), leaf area, leaf, stem and root weights, root length, leaf and stem soluble carbohydrate, adaxial and abaxial stomata density, and stomata conductance. Results showed high rates of grafting success indicating compatibility among the cacao genotypes. There were significant differences (P ≤ 0.05) in leaf development among the rootstock-scion combinations from 2 to 24 weeks after grafting. Amelonado and TC2 (AT; 22.35) combinations recorded significantly higher leaf soluble carbohydrate contents than Amelonado and Amelonado (AA; 11.78) combinations which recorded the lowest. Also, F3 Amazon and TC2 combination (FT; 21.32) had highest stem soluble carbohydrate contents. There were significant differences (P ≤ 0.05) among the combinations for stomatal properties (adaxial and abaxial stomata density), Amelonado and TC2 (AT) had the highest stomata density compared to other combinations. The rootstock-scion combinations affected graft union girth, leaf, stem and root weight and below graft union girth of cacao at 6 and 9 months after grafting (MAG). Amelonado and TC2 (AT) had widest leaf area and highest stomata conductance compared with other combinations. It is concluded that grafting involving rootstock-scion combinations from cacao genotypes affected the growth and development of grafted plants and measured functional traits (water soluble carbohydrate, chlorophyll contents, stomata characters and gas exchange) appeared important to the success of grafting in cacao.
Keywords: Cacao, grafting; rootstock; scion; genotypes; compatibility; vigour; quality, maturity, stress, tolerance