Combining Ability of Cocoa (Theobroma cacao L) Clones and Variability for Morphological Traits among Hybrids
Goodness U. Adebo *
National Horticultural Research Institute, P.M.B. 5432, Jericho, Ibadan, Nigeria.
Daniel B. Adewale
Department of Biological Sciences, Ondo State University of Science and Technology, P.M.B. 353, Okitipupa, Nigeria.
Malachy O. Akoroda
Cocoa Research Institute of Nigeria, P.M.B. 5244, Ibadan, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Aims: To estimate the general and specific combining ability (GCA and SCA) of some cocoa clones for some vegetative and pod trait and to quantify the extent of variability among the studied cocoa genotypes.
Place and Duration of Sample: The experiment was performed at Local Clone Trial plot, Cocoa Research Institute of Nigeria (CRIN), Ibadan between June 2013 and April 2014.
Methodology: Three cocoa testers (N38 – T3, T65/7 – T4, and T8/27 – T5) were crossed with two cocoa lines (T12/11 – L1, and T30/13 – L2). Generated pods were evaluated for girth (PG), thickness (PIT) and inner diameter (PIW). Seeds from the selfed and the hybrid pods were sown and established in a completely randomized design with three replications. Data on stem girth (SG), plant height (PH), number of leaves (NL), leaf length (LL), leaf width (LW), and petiole length (PTL) were taken at two weeks intervals for twelve weeks on the eleven cocoa genotypes.
Results: Line and tester analysis revealed significant (P ≤ 0.05) differences for treatment, parents, crosses, lines and line by tester sources of variation. The highest general combining ability (3.83) occurred in T3 for PH. The best (0.46) specific combiner for PG was L2 x T5, while L2 x T3 and L1 x T3 were the best combiners for PIT (0.18) and PIW (3.14) respectively. Analysis of variance also revealed significant (P ≤ 0.05) differences among the genotypes. T12/11 and T65/7 had the highest genetic similarity (0.86).
Conclusion: Hybrids from the crosses of the parents are new recombinants, adding to the cocoa germplasm size. The observed genotypic diversity forms a good basis for selection of traits to assist a further improvement of cocoa genotypes. Crosses with significant specific combining ability could be selected and use for implementing a more effective cocoa breeding programme.
Keywords: Cocoa, germplasm enhancement, genetic distance, diversity, hybrids