Genetic variation for vigour and yield of cocoa (Theobroma cacao L.) clones in Ghana

Abstract

The lack of agronomic information on germplasm clones has been suggested as one of the reasons for their poor utilization and management. Several cocoa genotypes from different genetic origin have been introduced into Ghana to broaden the crops genetic base. The present study investigates genetic variation and associations of vigour (estimated as stem diameter increments) and yield and its component traits (bean weight, number of beans per pod, pod value and yield efficiency) in 116 cocoa clones introduced into Ghana over different time periods. The clones were transplanted in June 2010, after eight-months of grafting, following a randomised complete block design with four replications consisting of four trees per clone per block. Stem diameter increments (SDI) in both juvenile and productive stage and yield component traits were evaluated between July 2010 and June 2015. Clone effects were highly significant (P<0.01) for all the traits except SDI in the productive stage. Pod value and bean yield varied from 14 to 57 and 183 to 952kg/ha, respectively. Heritability was generally low for all the traits and the highest observed (0.27±0.06) was for bean weight. A positive genetic correlation (r=0.47, P≤0.001) was observed between SDI in the juvenile stage and bean yield. Some of the best performing clones T65/238, ICS 40, T16/613, SGU 50 and T63/961 combined high yields with high bean weight and high yield efficiency. Results from the study indicate that there is considerable genetic variation for yield in the available germplasm clones, and yield increase could be achieved by developing hybrids from some of the best clones.