Yield Performance and Bean Quality Traits of Cacao Propagated by Grafting and Somatic Embryo-derived Cuttings

Abstract

<jats:p>Twelve cacao (<jats:italic>Theobroma cacao</jats:italic>) clones propagated by grafting and orthotropic rooted cuttings of somatic embryo-derived plants were grown on an Ultisol soil at Corozal, Puerto Rico, and evaluated for 6 years of production under intensive management. Year, variety, year × variety, and propagation treatment × variety interactions indicated significant effects for dry bean yield, number of pods produced, pod index, plant height, and stem diameter. Propagation treatments had a significant effect on dry bean yield and pod index but not on number of pods produced. Average yield across varieties for both propagation treatments was 2087.9 kg·ha<jats:sup>−1</jats:sup> per year of dry beans. There was a highly significant variety effect. ‘UF-668’ was the top yielder averaging 2536.7 kg·ha<jats:sup>−1</jats:sup> per year of dry beans; however, this yield was not significantly different from the average yield of varieties ‘TARS-30’, ‘TARS-1’, ‘TARS-13’, ‘TARS-14’, and ‘TARS-2’, which averaged 2427.0 kg·ha<jats:sup>−1</jats:sup> per year. Except for ‘UF-668’, the TARS varieties were released in 2009 as high-yielding selections. Propagation treatments had a significant effect on dry bean yield. Dry bean yield of varieties propagated by grafting was 7% higher (2166.7 kg·ha<jats:sup>−1</jats:sup> per year) than those propagated by orthotropic rooted cuttings of somatic embryo-derived plants (2009.2 kg·ha<jats:sup>−1</jats:sup> per year). This yield difference could not be attributed to grafted plants being more vigorous nor by differences in root architecture. The lowest pod index value in both propagation treatments was obtained by ‘UF-668’; however, pod index for this variety did not differ significantly from values for ‘TARS-2’ and ‘TARS-23’ in grafted plants and from ‘TARS-2’, ‘TARS-23’, and ‘TARS-1’ in plants propagated by orthotropic rooted cuttings of somatic embryo-derived plants. With few exceptions, flavor characteristics were not significantly affected by propagation treatments. Although there were significant differences between plant propagation treatments for some of the variables measured in this study, these were not of a magnitude that would preclude the use of somatic embryogenesis as a viable propagation system for cacao.</jats:p>

Challenges in Cocoa Pollination: The Case of Côte d’Ivoire

“…Flowering peaks are often preceded by increased temperature and rainfall, and occur at the onset of the rainy season, after which flower numbers gradually decline [45]. In West Africa, the major rainy season commences in April and climaxes in June, a period that is characterized by intense flowering (flowers on branches and trunks) [6]. In the minor rainy season (September-November), flowering intensity is lower (flowers on branches only).…”

“…In 2016, global average cocoa yield was 438 kg dry beans per ha and per year (480 kg per ha in West Africa), whereas it was shown in research stations that cocoa bean yield could attain up to 2000 kg per ha and per year [6].…”

Relationships among Bean Yield Traits in Some Cacao (Theobroma cacao L.) Genotypes

“…Seventy per cent (70%) of world cocoa beans are produced by small holders in West Africa whose yield has remained low [5]. Cocoa bean yield is influenced by the variety and age of plant [6]. Bean yield in cocoa is also negatively influenced by climatic changes and increased land use for food crops [5].…”

Supplemental and Synchronized Pollination May Increase Yield in Cacao

“…Field-based research on increasing cacao yields in intensified cultivation systems is rare (but see Bos et al, 2007;Carr and Lockwood, 2011;De Almeida and Valle, 2007;Goenaga et al, 2009Goenaga et al, , 2015Johns, 1999;Zuidema et al, 2005). Furthermore, field trials evaluating the yield of advanced cacao clones under optimal management practices (e.g., fertigation) across multiple locations are not uniformly established.…”

“…Furthermore, field trials evaluating the yield of advanced cacao clones under optimal management practices (e.g., fertigation) across multiple locations are not uniformly established. As a result, current yield potential estimations of advanced cacao clones (e.g., Aneani and Ofori-Frimpong, 2013;Bos et al, 2007;Falque et al, 1995Falque et al, , 1996Goenaga et al, 2009Goenaga et al, , 2015Groeneveld et al, 2010) are highly variable and there is a pressing need to evaluate further the yield-limiting factors for numerous clones under intensified management conditions.…”