Evaluation of Local and International Cacao Cultivars in Monoculture and Agroforestry Systems

Locally selected cultivars of cacao (Theobroma cacao) are supposedly better adapted to local environmental conditions compared with commercially selected cultivars. In this context, the objective of this study was to compare production and disease incidence of local cultivars with international cultivars and to test for interactions between cacao production systems and cultivars. In the 1990s, the Bolivian cacao farmers’ cooperative El Ceibo carried out a selection programme in the Bolivian Alto Beni region, by collecting germplasm from well-performing cacao trees, which originated from a governmental programme that distributed hybrid seeds to cacao farmers between the 1960s and 1980s. From the El Ceibo program, four cultivars were selected and tested together with four commercial cultivars and four full-sib families encompassing five different production systems: two monocultures and two agroforestry systems under organic and conventional management, and one successional agroforestry system without external inputs. The long-term field trial was established in 2009 by the research institute FiBL and local partners in the Alto Beni region, Bolivia. Data on cacao yield and fungal disease incidence was recorded for each tree every 15 days between 2015 and 2019. Across all years, the two monocultures were the most productive systems with an average production of 4.8 kg tree-1 (fresh beans with fruit pulp) under conventional and 4.3 kg tree-1 under organic management. Conventional and organic agroforestry systems obtained an average production of 2.7 kg tree-1, while the successional agroforestry system had an average production of 2.1 kg tree-1. The local cultivars showed significantly higher yield in the five production systems across all years. The two best performing cultivars showed an average production of 6.6 and 6.4 kg tree-1 (fresh beans), respectively. The international cultivars had an average production of 3.6 kg tree-1. The full-sib families performed very poorly with an average production of 1.3 kg tree-1. There was a significant interaction between production systems and cultivars. Nevertheless, the rank between cultivars across production systems did not really change. The incidence of fungal diseases was low in all systems and slightly lower in local cultivars compared with the international ones. Our results highlight the relevance of selecting local genetic material

Locally-selected cacao clones for improved yield: A case study in different production systems in a long-term trial

Ageing plantations, poor genetic material, soil degradation, pests and diseases are, among other factors, limiting cacao production. To meet the increasing demand for cacao in the absence of productivity gains, forests are cleared and the use of external inputs is generalised, with severe negative impacts on biodiversity and GHG emissions. The use of improved plant genetic material should support a sustainable increase of production. In this study, we evaluate and compare the yield performance of four locally-selected clones with those of four widely-used international clones in South America and four full-sib families (crosses of the same international clones). The research was conducted in a long-term trial in Bolivia with different production systems, including monocultures and agroforestry systems under organic and conventional farming and a successional agroforestry system without external inputs. Their cacao yields and the factors determining productivity (pod index, flowering intensity, pod load, pod losses, aboveground biomass, harvesting period) were assessed during 5 years. The cacao trees grown in the two monocultures had higher yields than those in the agroforestry systems. This was the result of higher aboveground biomass, flowering intensity and pod load, and similar pod losses due to cherelle wilt and fungal diseases in the former when compared with the latter. No differences between conventional and organic management were observed. We did not identify any genotypes performing better in a specific production system. On average, the local clones had twofold and five times higher yields than the international ones and the full-sib families, respectively. This was related to their higher total pod load, bigger pods and higher yield efficiency, i.e., higher yield per unit of tree biomass. However, the local clones had less flowering intensity, more cherelle wilt and similar losses due to fungal diseases to those of the international clones. This study clearly shows the need to invest in selection and breeding programmes using locally-selected genetic material to increase cacao production and support renovation/rehabilitation plans. Breeding genetic material that is adapted to low light intensities is crucial to close the yield gap between monocultures and agroforestry systems, and to further promote the adoption of the latter