Reciprocal differences and combining ability for growth and yield components in cacao ( Theobroma cacao L.): a case of r
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Reciprocal differences and combining ability for growth and yield components in cacao (Theobroma cacao L.): a case of recommended cacao varieties in Ghana Atta Ofori . Francis K. Padi
Received: 6 August 2020 / Accepted: 7 November 2020 Ó Springer Nature B.V. 2020
Abstract The inappropriate use of cacao clones either as female or male parents in seed gardens have been suggested as some of the reasons for the low yields of cacao hybrid varieties grown in West Africa. The concept of reciprocal effects in cacao crosses has not been well studied. To investigate the impact of maternal effect on growth and yield traits, reciprocal differences and combining abilities of recommended cacao parents in Ghana were evaluated. Six clones, comprising four important seed gardens clones used across West Africa and two clones previously used as standards in international breeding projects were crossed in a 6 9 6 complete diallel mating design to produce 30 F1 progenies. These progenies were tested in the field using a random block design with four blocks and elementary plots containing 20 plants. Growth and yield traits including stem cross-sectional area in juvenile stage, jorquette height, bean weight, number of beans per pod and bean yield were monitored over a 6-year period. Mean squares of general combining ability (GCA), specific combining ability (SCA) and reciprocal effects were significant for almost all the traits except jorquette height in SCA. This indicates that additive and non-additive gene effects are important in the inheritance of the traits. The presence of reciprocal differences for all traits A. Ofori (&) F. K. Padi Cocoa Research Institute of Ghana, Box 8, New Tafo, Akim, Ghana e-mail: [email protected]
suggests the influence of maternal effects in controlling the traits. Manual pollinations for commercial seed production should, therefore, follow established protocol and clones recommended as female and male parents used strictly as recommended. One of the standard clones, AMAZ15/15 had significant positive GCA effect for yield, and consistently produced progenies with high SCA values. It could be added to parental clones currently used in producing cacao varieties in the seed gardens in Ghana and other West African cacao growing countries. Keywords Bean weight Diallel General combining ability Improved varieties Specific combining ability
Introduction Cacao is a humid tropical crop grown in areas with high annual rainfall. The primary centre of origin is South America (Motamayor et al. 2008), but, because of its importance, it is now cultivated in most tropical regions. It is cultivated for its fruit, from which the seeds are used for the production of chocolates and confectionaries. Ghana is the second largest cacao producer in the world and the cultivation of the crop is estimated to employ about 800,000 household families (Ghana Cocoa Board 2019). The seed obtained from the cacao pod is a major contributor to Ghana gross
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