Parentage analysis and comparison of cocoa families derived from bi-parental crosses and open-pollination for vigor and precocity in recommended cocoa (Theobroma cacao L.) clones in Ghana

ABSTRACT

Bi-parental hybrids (BPHs) are recommended cocoa planting materials in Ghana and other West African countries. However, the inability to produce enough BPHs to meet farmers’ demand makes it almost impossible to avoid open-pollinated families (OPF) in the supply chain. To study the effects of OPF on cocoa production, parentage analysis, vigor, and precocity of seven BPHs generated from a 4 × 2 North Carolina II (NC II) incomplete mating design were compared with eight OPFs. The 15 cocoa progenies together with two checks of Guiana (GU) origin were evaluated in a randomized complete block design with four replications across five contrasting locations for stem diameter increment (SDI) and number of pods per tree (NP). Parentage analyses at 75 single nucleotide polymorphism (SNP) loci of leave samples from the 17 progenies revealed that the BPHs were of the appropriate female and male parents, while the OPF had varying number of male parents. The pollination effect (bi-parental vs open-pollinated progenies) was not significantly different for both traits, but the BPH was relatively better and surpassed on average the OPF by 3.5% for SDI and 7.8% for NP. Crosses involving GU 144/ C, T63/967, and T65/238 as females in both the OPF and BPH showed predominantly higher performance than those with PA 7 and T79/501 for both traits. Among the promising female parents, GU 144/C is the only one that is not in the seed gardens and could be added to parental clones currently used in producing cocoa varieties in the seed garden.

KEYWORDS:

• Clones
• parentage
• selfing
• seed garden
• Upper amazon origin

Disclosure statement

No potential conflict of interest was reported by the author(s).

Contribution of authors

Both authors contributed equally to both the establishment of the research and the writing of the manuscript.

Data archiving statement

No data has been submitted to any data base; the accessions used are described in table 1.

Ethical standards

The research conducted was in compliance with the laws of the country in which the research was conducted.

Additional information

Funding

The authors are grateful for the financial support by Ghana Cocoa Board and the World Cocoa Foundation project. We are also grateful to the field and technical staff of the Plant Breeding Division, CRIG, for their support and assistance. This work is published with the kind permission of the Executive Director of CRIG as manuscript no. [CRIG/03/2023/024/13].