Organic soil amendments can be used to reduce the environmental impact of cocoa farming, increase sustainability, and protect livelihoods. This study aimed to explore Ghanaian cocoa farmers’ awareness and usage of compost and biochar on their farms and to make recommendations to increase adoption. A survey was conducted with 150 cocoa farmers, randomly drawn from a population of 245 across five cocoa-growing districts and representing four different soil types across the five major agroecological regions where cocoa is grown in Ghana. The survey was followed by a focus group discussion to better understand responses to the survey questions. Farmers attributed low cocoa yields to declining soil fertility and the high cost of farm inputs, particularly chemical fertilisers. Although some farmers were aware of compost use in vegetable production, none of the farmers surveyed used compost or biochar on their cocoa farms. The findings suggest that the reason for the lack of adoption is limited awareness. However, farmers were willing to learn how to prepare compost and biochar or to buy these amendments. Therefore, embedding training on the preparation and use of compost and biochar into equitable and inclusive programmes led by the Ghanaian Cocoa Board (COCOBOD), licensed buying companies (LBCs), certification schemes (e.g. Rainforest Alliance, Fairtrade, Organic), and farmer associations (cooperatives) is key to increasing adoption, elevating sustainability, and improving livelihoods. These organisations could also collectively support and subsidise the production and application of organic amendments by enterprises as a service provided to farmers.

The depletion of soil nutrients and decline in yields on cocoa farms in west Africa over time force farmers to abandon their farms and look for new fertile land, thereby contributing to deforestation. Cocoa pod husks (CPH) are a major farm waste representing considerable export of nutrients from cocoa soils, particularly P and K. Here, the impacts of soil amendment with raw CPH residues, CPH compost, CPH biochar, or a CPH compost-biochar mixture on soil fertility, greenhouse gas (GHG) emissions, and nutrient losses via leaching were assessed in two laboratory experiments using two major soil types used for cocoa cultivation in Ghana (an acidic Ferralsol and an alkaline Nitisol). In Experiment 1, soil nutrient availability and CO2 and N2O emissions were quantified, whereas simulation and quantification of nutrient leaching were conducted in Experiment 2. Soil pH increased from 4.8 to 8.6 by 1.4- and 1.1-folds on average in amended Ferralsols and Nitisols, respectively. Soil electrical conductivity increased in soils amended with CPH compost and/or biochar. Addition of raw CPH caused remarkable microbial immobilisation of N and reduced N availability and leaching, whereas CPH compost and/or biochar addition increased soil nitrate availability but reduced soil ammonium availability. Leaching of Ca in Nitisols was reduced when CPH biochar was included in the soil amendment. While soil K availability increased in all amended soils, most notably when CPH biochar was included, soil P and Ca availabilities were greatest where CPH compost was included. Soil total GHG emission (CO2 plus N2O) increased in all amended Ferralsols and the Nitisols amended with CPH compost or raw CPH, with the latter remarkably increasing soil CO2 emission by up to 14.8-folds. Compared to sole CPH compost amendment, CPH compost-biochar mixture amendment reduced soil total GHG emission and N and P leaching. These findings show that composted and/or pyrolysed CPH can be judiciously used to enhance soil fertility in cocoa farms, particularly in acidic soils. Pyrolysed CPH is especially beneficial for reducing soil nutrient leaching and GHG emissions and thus for increasing the sustainability of cocoa production in Ghana and west Africa.

Despite multiple studies of the impact of climate change on temperate tree species, experiments on tropical and economically important tree crops, such as cacao (Theobroma cacao L.), are still limited. Here, we investigated the combined effects of increased temperature and atmospheric carbon dioxide concentration ([CO2]) on the growth, photosynthesis and development of juvenile plants of two contrasting cacao genotypes: SCA 6 and PA 107. The factorial growth chamber experiment combined two [CO2] treatments (410 and 700 p.p.m.) and three day/night temperature regimes (control: 31/22degree celsius control + 2.5 degree celsius C: 33.5/24.5 degree celsiusand control + 5.0 degree celsius: 36/27 degree celsius) at a constant vapour pressure deficit (VPD) of 0.9 kPa. At elevated [CO2], the final dry weight and the total and individual leaf areas increased in both genotypes, while the duration for individual leaf expansion declined in PA 107. For both genotypes, elevated [CO2] also improved light-saturated net photosynthesis (P-n) and intrinsic water-use efficiency (iWUE), whereas leaf transpiration (E) and stomatal conductance (g(s)) decreased. Under a constant low VPD, increasing temperatures above 31/22 degree celsius enhanced the rates of P-n, E and g(s) in both genotypes, suggesting that photosynthesis responds positively to higher temperatures than previously reported for cacao. However, dry weight and the total and individual leaf areas declined with increases in temperature, which was more evident in SCA 6 than PA 107, suggesting the latter genotype was more tolerant to elevated temperature. Our results suggest that the combined effect of elevated [CO2] and temperature is likely to improve the early growth of high temperature-tolerant genotypes, while elevated [CO2] appeared to ameliorate the negative effects of increased temperatures on growth parameters of more sensitive material. The evident genotypic variation observed in this study demonstrates the scope to select and breed cacao varieties capable of adapting to future climate change scenarios.

Ghana is the second largest producer of cocoa in the world and cocoa farming supports the livelihoods of 25-30% of Ghana's population. However, average yield is only about 30% of the potential yield. Cocoa farms established on recently cleared rainforest are initially productive, but then productivity declines as soils become depleted of nutrients. Further expansion of cultivated land by deforesting tropical rainforests is environmentally costly, socially unacceptable, and inherently unsustainable. Therefore, strategies are urgently required to maintain and restore the productivity of existing smallholder farms to close this yield gap and sustainably increase cocoa production to meet growing demand. In this narrative review we provide context to the issues and highlight recent advances that offer promising opportunities to restore the soil health of Ghana's cocoa farms and sustainably reduce the yield gap. The shade trees in traditional agroforestry farms help prolong productivity for longer by supporting soil ecological functions and this has sparked renewed interest in the establishment of sustainable agroforestry cocoa farms. The single rate and formulation of mineral fertiliser recommended to farmers nationwide fails to account for variability in the response of different soil types to inputs. Therefore, site-specific fertiliser recommendations that also quantify the benefits of organic amendments are emerging. Composting and returning cocoa pod husks to the soil offers a considerable opportunity to close nutrient cycles (particularly for P and K) on cocoa farms and to help build and maintain soil organic matter. However, research is required to overcome the risk that recycling cocoa pod husks may contribute to the spread of black pod disease. Soil health indicators that quantify the soil ecological functions provided by these sustainable land management practices require benchmarking to monitor the impact of these interventions.

Cacao is an important tropical crop and requires high-fertility soils for better growth and productivity; nevertheless, soils where this crop is grown are, in general, acidic and low in fertility. Therefore, germplasm with tolerance to soil acidity is desirable for cacao genetic improvement. The objective of this study was to evaluate cacao germplasm for early growth, nutrient concentration, and potential tolerance to soil acidity. A greenhouse experiment was conducted to evaluate 60 cacao genotypes with diverse geographic origins. Cacao seedlings were grown for six months in acid soil with and without lime. Growth parameters and the total concentration of N, P, K, Ca, Mg, Fe, Cu, Mn, and Zn were measured in shoots after harvest. Our results indicate that the best early growth predictors of acid soil tolerance are the number of leaves and root area. N, Ca, Mg, and K uptake may have a potential role in tolerance to soil acidity. Finally, the results revealed a large difference among cacao genotypes in terms of their responses to acid soil stress, which led to the selection of ten genotypes: CCN-51, PH-21, CCN-10, PAS-91, ICT-1087, ICS-95, UF-667, TSH-565, PH-144, ICT-1189 that are potentially tolerant to soil acidity and could be used for breeding acid soil-tolerant cacao varieties.

Climate change poses a significant threat to agricultural production in the tropics, yet relatively little research has been carried out to understand its impact on mature tropical tree crops. This research aims to understand the genotypic variation in growth and photosynthesis in mature cacao trees in response to elevated CO2 and water deficit. Six genotypes were grown under greenhouse conditions at ambient (ca. 437 ppm) and elevated CO2 (ca. 724 ppm) and under well-watered and water deficit conditions for 23 months. Leaf- and canopy-level photosynthesis, water-use efficiency, and vegetative growth increased significantly in response to elevated CO2. Water deficit had a significant negative effect on many photosynthetic parameters and significantly reduced biomass production. The negative effect of water deficit on quantum efficiency was alleviated by elevated CO2. Genotypic variation was observed in several parameters including stomatal conductance, stomatal density and index, quantum efficiency, and biomass production, indicating the potential to develop more climate-change-resilient genotypes that can cope with predicted future climate change conditions. Elevated CO2 reduced some of the negative effects of water deficit through changes in water-use efficiency and light utilisation and reduced the negative impact of water deficit on biomass accumulation, but this was genotype-specific.

Theobroma cacao is one of the most economically important tropical trees, being the source of chocolate. As part of an ongoing study to understand the diversity of the badnavirus complex, responsible for the cacao swollen shoot virus disease in West Africa, evidence was found recently of virus-like sequences in asymptomatic cacao plants. The present study exploited the wealth of genomic resources in this crop, and combined bioinformatic, molecular, and genetic approaches to report for the first time the presence of integrated badnaviral sequences in most of the cacao genetic groups. These sequences, which we propose to name eTcBV for endogenous T. cacao bacilliform virus, varied in type with each predominating in a specific genetic group. A diagnostic multiplex PCR method was developed to identify the homozygous or hemizygous condition of one specific insert, which was inherited as a single Mendelian trait. These data suggest that these integration events occurred before or during the species diversification in Central and South America, and prior to its cultivation in other regions. Such evidence of integrated sequences is relevant to the management of cacao quarantine facilities and may also aid novel methods to reduce the impact of such viruses in this crop.

Cocoa, Theobroma cacao, is an important tropical perennial crop grown widely in the humid tropics. The exchange of cocoa germplasm between germplasm collections and breeding centres is vital for varietal development. Intermediate quarantine facilities, such as the International Cocoa Quarantine Centre, Reading UK (ICQC-R) play a vital role in ensuring the transfer of germplasm whilst minimising the risk of spreading pests and diseases. Current screening procedures combine visual inspection and molecular techniques, which are effective in detecting Cocoa swollen shoot virus (CSSV), a badnavirus, which causes severe losses but are restricted to West Africa. However, the detection of latent or mild virus infections that produce no visual symptoms has been a challenge. Recently two badnavirus species of cocoa producing mild symptoms, cacao mild mosaic virus (CaMMV) and cacao yellow vein-banding virus (CYVBV), have been sequenced. Here, we report new assays for the detection of these two species, for the first time in non-symptomatic accessions. Evolutionary and bioinformatic analyses of the viruses suggest their most recent source was from Trinidad, though there is historic evidence that these viruses may have their origin in South America and then become widespread globally over the last century. We also report a novel colorimetric Loop-mediated isothermal amplification (LAMP) assay for the detection of CYVBV. This simple and accurate method could be employed in field virus testing.

The potential effect of climate change on regional suitability for cocoa cultivation is a serious economic concern for West Africa—especially for Ghana and Côte d’Ivoire, whose cocoa cultivation accounts for respectively ∼19% and ∼45% of world production. Here, we present a modelling and observational study of cocoa net primary productivity (NPP) in present day and future West African climates. Our analysis uses a data assimilation technique to parameterise a process-based land-surface model. The parameterisation is based on laboratory observations of cocoa, grown under both ambient and elevated CO2. Present day and end of 21st century cocoa cultivation scenarios are produced by driving the parameterised land-surface model with output from a high-resolution climate model. This represents a significant advance on previous work, because unlike the CMIP5 models, the high-resolution model used in this study accurately captures the observed precipitation seasonality in the cocoa-growing regions of West Africa—a key sensitivity for perennials like cocoa. We find that temperature is projected to increase significantly and precipitation is projected to increase slightly, although not in all parts of the region of interest. We find, furthermore, that the physiological effect of higher atmospheric CO2 concentration ameliorates the impacts of high temperature and variation in precipitation thereby reducing some of the negative impacts of climate change and maintaining NPP in West Africa, for the whole 21st Century, even under a high emissions scenario. Although NPP is an indicator of general vegetation condition, it is not equivalent to yield or bean quality. The study presented here is, nevertheless, a strong basis for further field and modelling studies of cultivation under elevated CO2 conditions.

Cocoa mirids are the most important insect pests of cocoa in West Africa. This study investigated the effect of environmental parameters that are modulated by overhead shade, that is, light intensity and temperature, on nutrient and phenolic concentrations in cocoa and their subsequent effect on mirid feeding. Eight-month-old cocoa seedlings were maintained for 50 days in two growth chambers set to day temperatures of 25 or 30 degrees C. Each chamber had sections with different light intensities (541, 365 and 181 mu mol m(-2)s(-1)photosynthetically active radiation [PAR]). For the field studies at Akim Tafo in Ghana, 8-month-old plants of three cocoa clones were subjected to shaded (PAR = 180 mu mol m(-2)s(-1), between 11:00 a.m. and 12:00 p.m.) and unshaded (PAR = 1,767 mu mol m(-2)s(-1), between 11:00 a.m. and 12:00 p.m.) treatments for 50 days after which nutrient measurements and mirid choice tests were carried out. No significant effect of environment was observed on the phenolic concentration of stems under controlled environment chamber conditions. However, in the field, the phenolic concentration of stems was significantly greater for unshaded compared with shaded plants (p= .04). Under controlled conditions, the leaf nitrogen concentration increased slightly with light intensity (p= .003). The same trend was seen in stems but only at 30 degrees C. In the field, the impact of overhead shade on nitrogen varied between cocoa clones. The concentration of carbohydrates in both leaves and stems in the field was higher under unshaded conditions. When subjected to feeding tests, stems from unshaded cocoa had significantly more mirid feeding lesions (p= .003) after 24 hr exposure to mirids compared to shaded cocoa. Mirid feeding therefore appears not to be deterred by the higher phenolic levels but rather there was a preference for cocoa tissue grown under unshaded conditions. These findings highlight the need to consider the growing environment of cocoa clones when screening for varieties with resistance to mirids.

AbstractA survey was conducted of Indonesian cocoa farms to assess the extent of yield variation and factors associated with this variation. The survey of 120 farms during the course of 3 years encompassed four provinces in Sulawesi (South, South-East, West and Central), Western Sumatra, Lampung, East Java and West Papua. A high degree of yield variation was observed between farms, the average over 3 years ranged from 39 to 3586 kg ha−1. Overall, yields were greater on farms that were classified as ‘highly managed’, compared to ‘moderately’ and ‘less managed’. Seasonal variability in yields was generally greater in districts with a more pronounced dry season such as South Sulawesi and Lampung. Multiple regression analyses revealed particular husbandry practices that were linked with higher cocoa yields. Specifically, the use of inorganic fertilisers, application of fungicides against blackpod and weeding were all practices that were associated with higher yields. A positive association between rainfall and yield was observed for the years 2014/15 and 2015/16 but not 2016/17, which was a La Niña year (when rainfall totals were higher). Some of the farms surveyed were planted with cocoa at very low densities implying an opportunity for yield improvement through gap filling or replanting at higher densities (although it was noted that some farmers maintained lower planting densities due to the cultivation of companion crops). Given the smallholder status of most cocoa farms in Indonesia (mean area in this study was 0.71 ha) it is important that farmers are able to maximise returns from their land in order to maintain a livelihood. This study illustrated the potential for yield improvement on Indonesian cocoa farms through adoption of best agronomic practice.

Cacao (Theobroma cacao L.) is a tropical perennial crop which is of great economic importance to the confectionary industry and to the economies of many countries of the humid tropics where it is grown. Some recent studies have suggested that climate change could severely impact cacao production in West Africa. It is essential to incorporate our understanding of the physiology and genetic variation within cacao germplasm when discussing the implications of climate change on cacao productivity and developing strategies for climate resilience in cacao production. Here, we review the current research on the physiological responses of cacao to various climate factors. Our main findings are as follows: (1) water limitation causes significant yield reduction in cacao, but genotypic variation in sensitivity is evident; (2) in the field, cacao experiences higher temperatures than is often reported in the literature; (3) the complexity of the cacao/shade tree interaction can lead to contradictory results; (4) elevated CO2 may alleviate some negative effects of climate change; (5) implementation of mitigation strategies can help reduce environmental stress; and (6) significant gaps in the research need addressing to accelerate the development of climate resilience. Harnessing the significant genetic variation apparent within cacao germplasm is essential to develop modern varieties capable of high yields in non-optimal conditions. Mitigation strategies will also be essential, but to use shading to best effect shade tree selection is crucial to avoid resource competition. Cacao is often described as being sensitive to climate change, but genetic variation, adaptive responses, appropriate mitigation strategies and interactive climate effects should all be considered when predicting the future of cacao production. Incorporating these physiological responses to various environmental conditions and developing a deeper understanding of the processes underlying these responses will help to accelerate the development of a more resource use efficient tree ensuring sustainable production into the future.

Establishment of young cacao trees in West Africa can be severely impeded by the onset of the dry season. To address this issue, a field experiment was conducted in Ghana to examine whether different mulch treatments and irrigation applied during the dry season combined with overhead shade could improve survival, early growth and yield of cacao. The mulch treatments used were polyethylene film and coffee husks placed around the young plants. Irrigation was used as a positive control, and no mulching or irrigation was a negative control. Three shade regimes were provided through different arrangements of Gliricidia sepium and plantains. Four different cacao clones were used in the study in a replicated split-plot design. Early growth of cacao was stimulated under the irrigation and plastic mulch treatments. Higher rates of photosynthesis during the dry season appeared to underlie these increases. Significantly higher early yields were also observed under the irrigation and coffee mulch treatments compared with the control. Plant survival varied significantly between treatments; irrigation was associated with the highest plant survival (94%), followed by the plastic mulch treatment (91%), coffee husk (82%) and the control (70%). There was also an increase in survival when more intense shading was used. Under zero mulch conditions, differences in survival were observed between clones. The clones P 30 [POS] and SCA 6 were more sensitive to drought (in terms of survival) than PA 150 and T 79/501. It is concluded that relatively simple mulching techniques or controlled irrigation in conjunction with appropriate shade management can significantly improve early establishment and cropping of cacao.

It is important for researchers, curators and breeders to have confidence in data being generated by germplasm evaluation and breeding programmes, and one of the key concerns is the true identity of the plants being used. Mislabelling of cocoa accessions is a significant problem, with estimates as high as 30%. Naming errors will have a large, detrimental impact on conservation, breeding and research, since mislabelled material is unlikely to exhibit the same genetic makeup or combination of traits as its true-totype namesake. Farmers may also receive poorly performing material as a result of mislabelling. Data gathered from a mislabelled accession will result in misleading recommendations or conclusions, such as the genetic gain reported by breeding programmes. Mislabelling events can also complicate the comparison of multiple data sets from different locations. It is particularly important to be able to link data to germplasm with confidence when combining the large trait evaluation and molecular analysis datasets necessary to identify and screen for key genes of interest. The importance of correctly identifying material has been widely recognised for many years and several groups are currently generating genetic fingerprints using SNP markers. However, reliable identification of individuals will only be possible if a single genetic fingerprint is established as a reference for all others to be compared to and a core set of markers are consistently used. With this in mind, the Reference Genotype Working Group was formed in May 2016 with the aim of coordinating the verification of cacao germplasm. This process has led to the development of an online tool to compare SNP profiles of individual trees and assign each a verification status; off-type, verified true-to-type or reference (original material if available). Although the tool can work with any number of SNP markers, the group have proposed a core set of widely-used markers to allow robust and consistent comparisons of profiles to be made across collections. The verification status of accessions in a collection will be included in the International Cocoa Germplasm Database (ICGD) and made widely available to the cocoa community, with web pages created to highlight reference genotypes and compare other genetic fingerprints to these. This paper describes the work of the Reference Genotype Working Group, initially focussing on the international collections and the International Cocoa Quarantine Centre (University of Reading), but with the intention to invite further collaboration from key partners and work towards the inclusion of other collections.

Atmospheric CO2 concentration continues to rise and is predicted to reach approximately 700 ppm by 2100. Some predictions suggest that the dry season in West Africa could be extended with climate change. This study examined the effects of elevated CO2 concentration and water deficit on growth and photosynthesis of juvenile cacao. Light-saturated photosynthesis (P (max)), quantum efficiency, and intrinsic water-use efficiency increased significantly in response to elevated CO2, as did a range of growth and development responses (e.g. leaf area and leaf number), but the magnitude of the increase was dependent on the water treatment. Stomatal index was significantly greater in the elevated CO2 treatment; an atypical response which may be a reflection of the environment in which cacao evolved. This study shows a positive effect of elevated CO2 on juvenile cacao which may help to alleviate some of the negative impacts of water deficit stress.

In order to access sufficient genetic diversity for cocoa breeding it is often necessary to import new genotypes. However, it is vital that such movement takes place within a quarantine framework to avoid introduction of pests and diseases. Safe movement procedures for cocoa germplasm are particularly important as many pests and pathogens of cocoa are confined to particular geographical regions. The International Cocoa Quarantine Centre at the University of Reading (ICQC,R) is the main hub for global movement of cocoa germplasm. The centre has been in operation since 1985 and has worked closely with the international genebanks to provide a safe transit route for germplasm to institutes working on cocoa in over thirty different countries. Rigorous testing procedures include virus indexing through a combination of graft testing and laboratory screening using a suite of PCR primers. Approximately 400 accessions are currently held at the ICQC,R, with current lists and further information available on the centre's website (www.icgd.reading.ac.uk/icqc/), which has links to the International Cocoa Germplasm Database (ICGD) enabling recipients of material to access associated data. The Technical Guidelines for the Safe Movement of Cacao Germplasm document, based on the original FAO/IPGRI Technical Guidelines, was updated extensively in 2010 by the CacaoNet Safe Movement Working Group to take into account a broader range of pest and disease threats. Subsequent revisions were made in 2014 and 2017. The guidelines serve as a reference point for the cocoa community and include information on the geographical spread of pests and diseases and sub-sections on particular pests and diseases that have been written by experts within those fields. Information includes physical symptoms, biology of the pathogen or insect pest and recommended quarantine measures. The guidelines have been published on-line and in physical form in English, French and Spanish under the umbrella of CacaoNet and will continue to be updated to incorporate new knowledge as it becomes available.

Aims: An experiment was conducted to investigate the effect of a wide range of temperatures on the growth and physiology of Theobroma cacao, to study the differences between night and day temperatures and to determine the optimum temperature for the cocoa growth. Study Design: The experiment used five combinations of night and day temperatures (18°C and 30°C [18N30N], 18°C and 36°C; [18N 36D], 24°C and 24°C [24N24D], 24°C and 30°C [24N30D] and 24°C and 36°C [24N36D]) using complete randomized design (CRD). Place and Duration of Study: Crops and Environment Laboratory University of Reading and International Cocoa Quarantine Centre, between 23rd May 2016 and 25th July 2016. Methodology: The cocoa seedlings were put into five growth cabinets with five different night and day temperatures combinations (18°C and 30°C, 18°C and 36°C, 24°C and 24°C, 24°C and 30°C, 24°C and 36°C) for two months (63 days) under controlled environment condition where the relative humidity and vapor pressure deficit were controlled. Destructive harvest data was taken at end of the experiment which included fresh weight, dry weight, leaf area and root weight. Non-destructive measurements were height of the plant, photosynthetic rate, chlorophyll fluorescence and total chlorophyll content. Results: Treatment 24N30D have the best growth and treatment 24N36D had the lowest growth performances compared to other treatments. Conclusion: The growth was not only dependent on the day temperature, but also on the night temperature. A large gap between night and day temperatures (DIF) reduced the cocoa growth. The result also showed the optimum temperature amongst those studied for cocoa growth is the combination of 24°C night temperature and 30°C day temperature.