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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 × 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 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. [ABSTRACT FROM AUTHOR]

Drought is the major abiotic stress limiting cocoa seedling survival during establishment. The level of genetic variation and relationship among traits related to drought tolerance were examined in a 6 × 6 incomplete diallel and 8 × 3 incomplete factorial mating designs for parents of diverse genetic groups. Thirty-eight families, 23 from the diallel and 15 from the factorial mating were evaluated in 2012/13 major dry season under shade and no-shade locations. Six-month old seedlings were planted in a randomized complete block design with two replications consisting of 24 plants per plot. Traits related to drought tolerance including stem growth, percentage survival, leaf chlorophyll content and plant vigour were monitored. Analysis of the 38 families showed highly significant ( P ≤ 0.01) variation for families, replications, locations and location × family interaction for most of the traits. Preponderance of additive effects was manifested in terms of significant GCA when genetic analysis of the diallel was performed. Heritability was moderate to high ( hb = 0.43-0.63) for broad sense and low to moderate ( hn = 0.25-0.57) for narrow sense. Clones PA 13 and AMAZ 15/15 had positive GCA effects, whereas PA 150 and T60/887 had negative GCA effects for most traits. The highest genotypic correlations were between survival and vigour. Results from the study indicate that there is considerable genetic variation for traits related to drought tolerance in the available germplasm, and the families of some specific clones are able to survive droughts under typical field conditions in Ghana. [ABSTRACT FROM AUTHOR]