Search

The cacao swollen shoot disease (CSSD) caused by a complex of badnavirus species presents a major challenge for cacao production in West Africa, especially Ghana and Côte d'Ivoire. In this study, CSSD species detection efficiency, diversity, and geographic distribution patterns in cacao plantations in Ghana and Côte d'Ivoire were investigated through field surveillance, PCR detection assays, sequencing of positive amplicons, and phylogeographic clustering. Cumulatively, the detection efficiency of the tested CSSD primer sets that were targeting the movement protein domain of the virus ranged from 0.15% (CSSD-3 primer) to 66.91% (CSSD-1 primer) on all the symptomatic cacao leaf samples assessed. The identified CSSD species differed phylogenetically and overlapped in distribution, with the cacao swollen shoot Togo B virus (CSSTBV) (n = 588 sequences) being the most prevalent and widely distributed compared to the other CSSD species that were encountered in both countries. Geographically, the cacao swollen shoot CE virus (CSSCEV) species (n = 124 sequences) that was identified was largely restricted to the bordering regions of Ghana and Côte d'Ivoire. These results provide updated knowledge of the geographic distribution of the key CSSD species and their diagnostic efficiency and, thus, provide guidance in identifying locations for structured testing of cacao germplasm and optimal diagnostics for the predominant CSSD species in Ghana and Côte d'Ivoire. [ABSTRACT FROM AUTHOR]

The cacao swollen shoot virus disease (CSSVD) is among the most economically damaging diseases of cacao trees and accounts for almost 15–50% of harvest losses in Ghana. This virus is transmitted by several species of mealybugs (Pseudococcidae, Homoptera) when they feed on cacao plants. One of the mitigation strategies for CSSVD investigated at the Cocoa Research Institute of Ghana (CRIG) is the use of mild-strain cross-protection of cacao trees against the effects of severe strains. In this study, simple deterministic, delay, and stochastic ordinary differential equation-based models to describe the dynamic of the disease and spread of the virus are suggested. Model parameters are estimated using detailed empirical data from CRIG. The modeling outcomes demonstrate a remarkable resemblance between real and simulated dynamics. We have found that models with delay approximate the data better and this agrees with the knowledge that CSSVD epidemics develop slowly. Also, since there are large variations in the data, stochastic models lead to better results. We show that these models can be used to gain useful informative insights about the nature of disease spread. [ABSTRACT FROM AUTHOR]

The cocoa swollen shoot virus disease persists in Ghana in spite of the implementation of an eradication campaign against the disease by the government since 1948. Two major factors are identified as limiting the success of the eradication campaign. First, the extension problem, namely, the low level of growers' knowledge (know-why) concerning the disease, including knowledge of the causal agent (3.8%), the vectors (2.3%), and the recommended preventive measures (8% to 67%). Second, the implementation problem, namely, the failure of growers and government-employed labourers to follow the recommended policy of cutting-out and replanting cocoa farms. Thus, about half (51%) of the affected farms were not correctly treated, despite the specialized labour provided and paid for by the government to implement treatment. In addition, about 73% of the growers who treated their affected farms without government support did so incorrectly. Other factors include the direct treatment cost (US $513.00 ha−1) to be borne by growers, as well as land tenure arrangements, and the waiting time of at least three years before the first harvest after replanting. A more researcher-grower collaborative approach in managing the disease could enhance growers' knowledge and the adoption of recommended practices to limit the spread of the disease. In addition, policy decisions on a nationwide disease management strategy that require growers' collective efforts should consider growers' socio-economic conditions like land tenure arrangements and disease treatment cost (direct and indirect) incurred by growers. [ABSTRACT FROM AUTHOR]

Cacao swollen shoot disease (CSSD) caused by complexes of cacao swollen shoot badnaviruses (family Caulimoviridae, genus Badnavirus) remains highly prevalent and devastating in West Africa. The disease continues to impact substantially on cacao yield loss, cacao tree mortality, and decline in foreign exchange income from cacao bean sales. Currently, the disease is estimated to have a prevalence rate of over 30% in Ghana, as assessed in the ongoing third country-wide surveillance program. Although achievements from past research interventions have greatly elucidated the etiology, biology, epidemiology, diagnostics, and management of the disease, there are some outstanding knowledge gaps. The role of these information gaps and their effect on CSSD epidemiology and prevalence remain unanswered. This paper summarizes existing scientific knowledge from past research achievements that have provided elucidation on CSSD epidemiology, management options, and guided future research. The discussion highlights the need for multidisciplinary research with modern tools and institutional collaborators to holistically bring clarity on knowledge gaps on pathogen biology, virus–host-–vector interactions, role of environmental and soil nutrient effects on CSSD severity, evolution pattern, role of alternative hosts on virus species diversity, vector population dynamics, and their overall impact on CSSD prevalence and integrated management in cacao plantations. [ABSTRACT FROM AUTHOR]

Soil organic carbon and main nutrient stocks play key roles in maintaining soil fertility and yields of agricultural crops including cocoa (Theobroma cacao). The amount of nutrients removed from the soil by the cocoa trees could be influenced by its physiological growth stage. A study was carried out to examine the changes in some soil physical and chemical properties with main nutrients availabilities under cocoa plantations at the Cocoa Research Institute in the Eastern Region of Ghana. Cocoa plantations of different ages (5, 10, 14, 18 and 23 years) were chosen based on similar land history. Soils at the study sites are classified as Xanthic Ferralsol (WRB series). On each plantation, one acre (0.4ha) plot was demarcated and divided into three blocks for soil sampling. Five core samples were taken at 0–15 cm depth per block, bulked together and subsample taken to the laboratory for analyses. Particle size analyses showed that all soils were of sandy loam texture. All soils were acidic with pH below 5.5, relatively low exchangeable K and Ca. Bulk density values varied with ages at highest in 18 years. Soils under 23 years old plantations had relatively lower bulk density than those of the other ages. Total nitrogen content under the 5, 10, and 18 years of cocoa plantations was below the critical values considered adequate for good cocoa growth. Soil carbon stock and available phosphorus content of the soil generally tend to increase with age of the cocoa plantations. These differential variations in the soil nutrients, namely, total N, available P, exchangeable K, Ca, and Mg among five different cocoa plantation ages suggest that total nitrogen, available P, and exchangeable Mg were higher than the critical levels for good cocoa growth under 23 years of cocoa plantations only, but exchangeable K and Ca were lower the critical levels for all ages of cocoa plantations. [ABSTRACT FROM AUTHOR]

Cocoa swollen shoot virus disease (CSSVD) is a major disease of cacao (Theobroma cacao L.) in Ghana and other West African countries that grow the crop. Attempts to develop resistant varieties since the discovery of the disease in 1936 have yielded little success. Recently, planting materials that are tolerant to the disease have been recommended for planting in areas with high CSSVD prevalence. However, the effect of CSSVD on yield component traits of most cacao clones including the tolerant varieties has not been well studied. To investigate the impact of CSSVD on these traits, reduction in bean weight (BW), number of beans per pod (NoBP) and dry bean yield (DBY) between symptomless and symptomatic trees, and disease incidence (DI) among 210 different cacao clones were evaluated. The clones were transplanted in June 2010 following a randomised complete block design with four replications consisting of three trees per clone per block. Response of the clones to CSSVD incidence had 180 of the genotypes having < 50% symptoms. Clones of Contanama, Iquitos, Marañon, Nanay and unknown derived from Upper Amazon parentage had less DI at the end of the study. The CSSVD effect (symptomless vs. symptomatic) was significant (p < 0.05) for DBY and NoBP, and the symptomless trees surpassed on average their symptomatic trees by 21.17% for DBY. Some of the best-performing clones identified under natural CSSVD infection were; COCA 3348/52 and GU 219/V among the underrepresented clones, B 36, ICS 40, NA 33 x IMC 67, T30/628, T60/887, T63/971, T 81/1879 and T 82/503 among those that combine high DBY with low yield reduction, and NA 124, T17/358, T35/78, T57/305, T63/971 x SCA 6, T65/239, T76/1835 and T82/2294 among those that combine high DBY with no disease incidence. Their inclusion in breeding programs that seek to develop resistant CSSVD varieties or deployment as planting materials in endemic areas to improve yield production in Ghana is recommended on the basis of the present observations. [ABSTRACT FROM AUTHOR]

Cocoa swollen shoot virus disease (CSSVD) has for over seven decades been managed in Ghana through the 'cutting out method'. This procedure involves complete removal of infected cocoa trees together with neighbouring apparently healthy cocoa trees from affected farms and replanting with improved cocoa varieties tolerant to the virus. This method of control started in 1946 with the objective to eradicate and also limit the spread of the virus to only severely affected farms in Ghana. Farmers whose farms are 'cut out' of infected cocoa trees are assisted to regenerate their farms with improved cocoa varieties tolerant to the virus. In practice however, this approach have several times been opposed by farmers leading to its intermittent suspension. Farmers rather prefer to allow CSSV infected trees to remain on their farms to produce few pods as source of income than to allow them to be removed. Delayed funding of the programme coupled with or without payment of monetary compensation to farmers often results in time lags between outbreak identification and farmers willingness to allow infected trees to be removed. This among other challenges of the programme have accounted for the increased prevalence and the continuous spread of the disease in Ghana. This paper provides empirical analysis of cocoa tree removals from 1945/46 to 2013/2014 when the programme has been continuously implemented across the cocoa regions in Ghana and discusses some of the key challenges on the implementation of the 'cutting out' method and offers some perspectives for its use to manage the spread of the disease. [ABSTRACT FROM AUTHOR]

Cacao swollen shoot virus causes cacao swollen shoot disease of Theobroma cacao (cacao) plants. At least six cacao-infecting Badnavirus species- Cacao swollen shoot Togo A virus , Cacao swollen shoot Togo B virus (previously known as Cacao swollen shoot virus ), Cacao swollen shoot CE virus , Cacao swollen shoot Ghana M virus , Cacao swollen shoot Ghana N virus , and Cacao swollen shoot Ghana Q virus -are responsible for the swollen shoot disease of cacao in Ghana. Each of these species consists of a multiplicity of strains. The New Juaben strain, the most virulent cacao swollen shoot virus strain in Ghana, belongs to the Cacao swollen shoot Togo B virus species, and is a commonly used strain in laboratory transmission assays. Infection of cacao trees with multiple strains of the virus is common and new evidence suggests that these coinfections may have resulted in the emergence of recombinant strains of the virus. The impact of these emerging recombinant strains on disease severity is uncertain. This review focuses largely on the discovery of cacao swollen shoot virus in Ghana, diversity of the virus strains, molecular characterization, propagation of virus infection in cacao plants, emergence of recombinant virus strains, vector-mediated transmission of the virus, and the management of the cacao swollen shoot disease in Ghana. It also contains sections on the botany and origin of the cacao tree, its introduction to Ghana, the role of cacao swollen shoot disease in facilitating Ghana's independence from Britain, and a brief history of chocolate., Competing Interests: The author(s) declare no conflict of interest.