Morphological Characterization and Genetic Diversity Analysis of Cacao ( Theobroma cacao L.) Genotypes from Sierra Leone

Abstract

Cacao ( Theobroma cacao L.) contributes to 60% of income of smallholder cocoa farmers and to the gross domestic product (GDP) of Sierra Leone. Despite its huge importance to the economy, production efficiency has been sub-optimal due primarily to the low yields, a consequence of the severe dearth of improved planting materials. Dearth of information on extent of genetic variability and genetic parameter estimates in cocoa limits its genetic improvement. This study assessed the genetic diversity and relationships using agro-morphological markers to determine the genetic parameter estimates of cocoa genotypes in Sierra Leone. Morphological classification categorized the germplasm into four main cluster groups. Findings showed that leaf length (LL), leaf width (LW), leaf area (LA), stem diameter (SD), pod diameter (PDIA), pod set percent (PSP), number of pods per tree (NPT), pod length (PL), pod size or area (PSA), number of beans per pod (NBP), dry bean weight per pod (DBWP), and estimated dry yield per tree (EDYT) had high heritability, pod width (PW) and pod thickness (PT) had intermediate heritability. High genetic advances, high phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) were also recorded. The PCV values were higher than GCV, indicating the influence of the environment in the studied traits. Significant and strong positive correlations were observed between pod size (PS) and pod width (PW) (r = 0.91**), DBWP and NPT (r = 0.73**), EDYT and NPT (r = 0.87**), LA and LL (r = 0.90*) and between LA and LW (r = 0.89**), LW and LL (r = 0.61**), SD and EDYT (r = 0.68**), SD and NPT (r = 0.75**), EDYT and DBWP (r = 0.84**), SD and DBWP (r = 0.62**); and intermediate positive correlations between PST and NTP (r = 0.60**), DS and PSP (r = 0.56**), and between PSP and EDYT (r = 0.52**). Significant and strong negative correlations were also found between LL and PW (r = −0.70**), LA and PL (r = −0.80**), PSP and NFT (r = −0.70**). Findings are useful for conservation and genetic improvement of the crop. This is the first report of cocoa genotypes performance evaluation in Sierra Leone that could be utilized in future cocoa improvement efforts.