Crop production and cocoa varieties
Climate change impact
Prolonged dry periods, droughts, and changing pest and disease dynamics threaten the future cocoa yields of farmers in many current production sites. Breeding of new cocoa varieties with increased water use efficiency, higher yields, and resistance to pests and diseases could help tackle these issues but the process is slow as there are significant barriers to the development and testing of improved cocoa varieties. Higher and less vulnerable yields could potentially reduce the incentive for farmers to increase production through land expansion.
Description of practices
At present, seedling gardens and small-scale breeding programs combined with other CSC practices probably provide the best results in terms of yields and income stability. Smallholder adoption of improved planting materials is perceived as being more likely than other management practices because of its ease and the familiarity of farmers with the concept of plant selection. In fact, farmer knowledge and participation in breeding programs can be useful input of expert farmers for a more dynamic and successful selection process of cocoa planting material (Aikpokpodion, et al. 2003). Hybridization between high-quality parents can also be a mechanism for increasing resilience and yields (Nair, 2010). Grafting of clonal varieties is becoming increasingly common (Vaast and Somarriba 2014), but it requires farmer training on proper technique and access to improved varieties for grafting. Lastly, pod inoculation has proven successful in providing resistance to moniliasis in Costa Rica and Ecuador (Eskes, 2017) but requires testing in other regions.
State of the art
Some authors consider that breeding more resilient varieties is key to increasing yields in the future (Vaast and Somarriba 2014). Nonetheless, progress has been slow and breeding programs have yet to provide significant large-scale benefits to farmers. Efron, et al. (2003) list the focus on disease resistance, heterozygosity of parental clone hybrids and lack of use of proven breeding procedures as barriers to progress in breeding. Furthermore, training and input access will be needed to increase the efficiency in managing improved cocoa varieties (Eskes, 2017). Cocoa has a low heritability of traits, this means that single tree selection of planting material is often insufficient (Eskes, 2017). Cocoa breeding programs have also been stalled by conflicting objectives. There are many priorities to breeding: flavor, adaptation to the environment, tree shape, pod size, bean characteristics, etc.
Cocoa breeding objectives:
- Increasing yield
- Lower susceptibility to pests and diseases
- Greater resilience to climatic events (e.g. droughts and flooding)
- Capacity for increased planting density
- Improving flavor
- Increase cocoa butter content
- Increase production stability
- Reduce management and input costs
- Minimize interplant competition
There have been no substantial improvements in cocoa breeds in the past decades and more research into disease and climate change resistance is required (Nair, 2010). A common problem with the evaluation of cocoa outcomes persists in the analysis of variety yields and resilience: field studies are costly in terms of land and labor, especially when searching for long-term effects. The application of modern breeding to cocoa is relatively recent compared to other crops. Studies on cocoa varieties should be subject to certain standards and resistance evaluation methodologies for study and variety comparability (DuVal, et al. 2017). Future breeding programs must also consider environmental change, changes in cocoa production systems, and farming practices. The availability of improved varieties through seed gardens should be increased and more research into clonal garden technology is required. The establishment of regional cocoa centers could foster the development of varieties for local contexts and information sharing between these centers would speed up progress considerably (Efron, et al. 2003).
Importance in terms of CSA
Productivity: New breeds and varieties of cocoa have been hailed as the solution to increasing yields, tolerance to extreme climatic events, pests and diseases, etc. Higher yields and lower losses due to pests and diseases significantly increase cocoa productivity
Adaptation: The development of cocoa breeds that are more productive and tolerant to environmental stresses will become more important as the occurrence of these stressors increases in scope and intensity. Replanting and establishment with improved seeds improves adaptation to future environmental stressors.
Mitigation: New cocoa varieties generate the possibility of increasing cocoa yields on current farmland reducing the need for encroachment on forests and deforestation. One of the targets of breeding programs in increasing the plant density which would also contribute to increasing the carbon sink properties of the cocoa ecosystem. In addition, the planting of more pest resistant varieties entails reductions in the need of chemical pesticides which can be damaging to the environment and the biodiversity of cocoa ecosystems.
Complexity and link to other practices
Depending on the traits of the grafted, hybrid, or improved cocoa plant other farming practices will have to be adapted. Some hybrid characteristics and inoculations have been found to have a direct influence on the fermentation of cocoa (Ramos, et al. 2014). Higher yielding varieties may contribute to greater soil nutrient depletion increasing the need for fertilizer applications, mulching, and other soil management practices. Improved water use efficiency and resilience to droughts affect water management practices, while pest and disease resilient varieties reduce pesticide requirements and costs related to sanitary pruning. The structure of agroforests also changes if improved cocoa varieties can be planted at higher densities.
– Eskes, A.B., 2011. Collaborative and participatory approaches to cocoa variety improvement. Final report of the CFC/ICCO/Bioversity project on cocoa productivity and quality improvement: a participatory approach (2004–2010). CFC, Amsterdam, The Netherlands/ICCO, London, UK/Bioversity International, Rome, Italy, 205.
Case study 1: Brazil
Canopy characteristics of contrasting clones of contrasting clones of cacao (Theobroma cacao) – Daymond, et al. 2002
The Bahia region of Brazil is often used for the study of cocoa trees and interventions. In this case, the canopy characteristics of different clonally propagated cocoa cultivars were studied for a period of 14 months. This falls inside the framework of resource capture which had been applied previously to other crops. Despite the extension of cocoa cultivation in the tropics, cocoa clones used for planting are typically collected from the wild, breeding may improve crop characteristics including the canopy type.
Relation to CSA
Cocoa agroforestry production systems are often associated with decreased yields due to lower light interception light and soil nutrient competition. Breeding programs tend to focus on increasing yields, climate resilience, nutrient efficiency, and pest and disease tolerance. The breeding of more photosynthetically efficient cacao may reduce the differences in yield between agroforestry and full-sun cultivation, making the former more attractive because of its provision of additional income sources and ecosystem services. The optimal leaf-area index in varieties with a high level of self-shading was found to be lower, suggesting that these trees would benefit relatively more from pruning. Canopy characteristics will also determine optimal tree density; cocoa with slow-growing canopies may be more apt for higher density planting. Resource capture variation –which is highly inheritable- should be studied in combination with harvest indexes for studies in yield improvement.
Case study 2: Papua New Guinea
The relationship between vigor, yield and yield efficiency of cocoa clones planted at different densities. – Efron, et al. (2003)
Based on previous research and their own breeding program carried out in Papua New Guinea, the authors analyze the responses of cocoa breeds that vary in their vigor, more specifically in the area of their trunk cross-section. Nice advanced cocoa clones were studied, three clonal size groups (big, intermediate, and small) and two controls were planted in two locations. Each group of clones was planted at different densities (625 and 1000 trees per hectare). Because more vigorous clones have higher potential yields, trunk circumference and yield efficiency were measured.
Relation to CSA
Cocoa breeding is often viewed as a panacea to solve the problems of poverty, deforestation, pest and disease tolerance and climate change resilience. The research presented in this article underscores the importance of additional factors and practices to achieve optimal results. Different clonal varieties will have different planting densities for maximum yields and income and they may require the application of additional practices considered in CSC, such as pruning, to achieve the best results. Yield efficiency was highest among small clones regardless of tree planting density. The authors note that “selection of clones based only on yield potential will tend to favor the more vigorous clones”. Cocoa breeding programs should consider that yield efficiency, as it relates to yield and vigor, is also dependent on the planting density at establishment and pruning practices of farmers. Results should be retested in small-scale fields. High-density planting has an annual additional cost estimated at US$48.60, which may pose a barrier to smallholder farmers initially.