Physiological and growth responses of cacao to glyphosate exposure.

Herbicide drift phytotoxicity is a problem in plantation crops due to application failures and unfavorable spray conditions. With the increased use of glyphosate in cacao plantations in Ghana, there are concerns about the effect on cacao growth and productivity from doses that potentially could be expected from drift. The aim of this study was to evaluate the physiological and growth response of young cacao plants exposed to glyphosate. Two field experiments were conducted in randomized blocks, with four replications. Glyphosate was applied at rates 0 to 720 g a.e. ha-1. Crop injury, shikimate accumulation, chlorophyll content, quantum efficiency of PSІІ (Fv/Fm), height, and stem diameter were evaluated. Increased glyphosate rates increased crop injury and shikimate accumulation and decreased chlorophyll content, quantum efficiency of PSІІ (Fv/Fm), and plant growth. Glyphosate rates 360 g a.e. ha-1 or higher resulted in >60% foliar injury and more than 10-fold increase in shikimate accumulation. Glyphosate reduced chlorophyll content to <10 and Fv/Fm to <0.35 at the highest rates. Glyphosate rates ≥180 g a.e. ha-1 reduced height and stem diameter of plants and caused reductions in stand count. Thus, cacao showed sensitivity to glyphosate, and severe injury impaired plant growth.

Climate change could reduce and spatially reconfigure cocoa cultivation in the Brazilian Amazon by 2050.

Cocoa is a plant with origins in northwestern South America with high relevance in the global economy. Evidence indicates that cocoa is sensitive to a dry climate, under which crop production is reduced. Projections for future climate change scenarios suggest a warmer and drier climate in the Amazon basin. In this paper, we quantify the potential effects in cocoa production due to its edaphoclimatic suitability changes to the Brazilian Amazon biome and account for regional differences in planning occupation territories. We modeled the suitability of cocoa's geographical distribution using an ensemble of 10 correlative models that were run in the "biomod2" library and projected to two future climate scenarios (RCPs 4.5 and 8.5) by 2050. Combining information on climate and soil suitability and installed infrastructure in the macro-regions of the Brazilian Amazon. We defined a zoning system to indicate how cocoa production may respond to climate change according to the current and future suitability model. Our results suggest that a reduction in precipitation and an increase in temperature may promote a reduction in the suitability of cocoa production in the Brazilian Amazon biome. In addition of the areas suitable for cocoa plantation, we found a 37.05% and 73.15% decrease in the areas suitable for intensification and expansion zones under RCP 4.5 and 8.5, respectively, compared with the current scenario. We conclude that there may be a need to expand land to cocoa production in the future, or else it will be necessary to plant a cocoa variety resistant to new climatic conditions. Besides, we recommend procedures to combat illegal deforestation to prevent the most critical climate change scenarios from occurring.

Aroma Properties of Cocoa Fruit Pulp from Different Origins.

Cocoa pulp occurs as a by-product of cocoa bean production and can be repurposed to different food applications, such as jams, fruit preparations and beverages, improving the sustainability of cocoa production, as well as the livelihoods of cocoa farmers. In this work, aroma-active compounds of fresh cocoa fruit pulps from different origins were investigated by applying aroma extract dilution analyses in combination with gas chromatography-mass spectrometry/olfactometry for identification. In total, 65 aroma-active compounds were determined in four different pulps originating from Indonesia, Vietnam, Cameroon, and Nicaragua. Vietnamese pulp showed the highest number of aroma-active regions, while Cameroonian pulp accounted for the lowest. Moreover, Cameroonian cocoa pulp showed the lowest FD factors. Overall, the odorants with the highest FD factors were trans-4,5-epoxy-(E)-decenal, 2- and 3-methylbutanoic acid, 3-(methylthio)propanal, 2-isobutyl-3-methoxypyrazine, (E,E)-2,4-nonadienal, (E,E)-2,4-decadienal, 4-vinyl-2-methoxyphenol, δ-decalactone, 3-hydroxy-4,5-dimethylfuran-2(5H)-one, dodecanoic acid, and linalool. This study provides insights into the aroma composition of fresh cocoa pulp from different origins for future food applications.

Genomic structural variants constrain and facilitate adaptation in natural populations of Theobroma cacao, the chocolate tree.

Genomic structural variants (SVs) can play important roles in adaptation and speciation. Yet the overall fitness effects of SVs are poorly understood, partly because accurate population-level identification of SVs requires multiple high-quality genome assemblies. Here, we use 31 chromosome-scale, haplotype-resolved genome assemblies of Theobroma cacao-an outcrossing, long-lived tree species that is the source of chocolate-to investigate the fitness consequences of SVs in natural populations. Among the 31 accessions, we find over 160,000 SVs, which together cover eight times more of the genome than single-nucleotide polymorphisms and short indels (125 versus 15 Mb). Our results indicate that a vast majority of these SVs are deleterious: they segregate at low frequencies and are depleted from functional regions of the genome. We show that SVs influence gene expression, which likely impairs gene function and contributes to the detrimental effects of SVs. We also provide empirical support for a theoretical prediction that SVs, particularly inversions, increase genetic load through the accumulation of deleterious nucleotide variants as a result of suppressed recombination. Despite the overall detrimental effects, we identify individual SVs bearing signatures of local adaptation, several of which are associated with genes differentially expressed between populations. Genes involved in pathogen resistance are strongly enriched among these candidates, highlighting the contribution of SVs to this important local adaptation trait. Beyond revealing empirical evidence for the evolutionary importance of SVs, these 31 de novo assemblies provide a valuable resource for genetic and breeding studies in Tcacao.

Inter-species functional compatibility of the Theobroma cacao and Arabidopsis FT orthologs: 90 million years of functional conservation of meristem identity genes.

BACKGROUND: In angiosperms the transition to flowering is controlled by a complex set of interacting networks integrating a range of developmental, physiological, and environmental factors optimizing transition time for maximal reproductive efficiency. The molecular mechanisms comprising these networks have been partially characterized and include both transcriptional and post-transcriptional regulatory pathways. Florigen, encoded by FLOWERING LOCUS T (FT) orthologs, is a conserved central integrator of several flowering time regulatory pathways. To characterize the molecular mechanisms involved in controlling cacao flowering time, we have characterized a cacao candidate florigen gene, TcFLOWERING LOCUS T (TcFT). Understanding how this conserved flowering time regulator affects cacao plant's transition to flowering could lead to strategies to accelerate cacao breeding. RESULTS: BLAST searches of cacao genome reference assemblies identified seven candidate members of the CENTRORADIALIS/TERMINAL FLOWER1/SELF PRUNING gene family including a single florigen candidate. cDNA encoding the predicted cacao florigen was cloned and functionally tested by transgenic genetic complementation in the Arabidopsis ft-10 mutant. Transgenic expression of the candidate TcFT cDNA in late flowering Arabidopsis ft-10 partially rescues the mutant to wild-type flowering time. Gene expression studies reveal that TcFT is spatially and temporally expressed in a manner similar to that found in Arabidopsis, specifically, TcFT mRNA is shown to be both developmentally and diurnally regulated in leaves and is most abundant in floral tissues. Finally, to test interspecies compatibility of florigens, we transformed cacao tissues with AtFT resulting in the remarkable formation of flowers in tissue culture. The morphology of these in vitro flowers is normal, and they produce pollen that germinates in vitro with high rates. CONCLUSION: We have identified the cacao CETS gene family, central to developmental regulation in angiosperms. The role of the cacao's single FT-like gene (TcFT) as a general regulator of determinate growth in cacao was demonstrated by functional complementation of Arabidopsis ft-10 late-flowering mutant and through gene expression analysis. In addition, overexpression of AtFT in cacao resulted in precocious flowering in cacao tissue culture demonstrating the highly conserved function of FT and the mechanisms controlling flowering in cacao.

Growth, respiration and physicochemical changes during the maturation of cacao fruits.

BACKGROUND: Cacao is important for the economy of many countries in the humid tropics. Its quality is affected when fruits are not collected at the optimal harvest point. The aim of this study was to obtain maturity indices for producers to facilitate the timely harvest and improve the development of fermentation and the sensorial quality of cacao. The growth and respiration processes, and the physicochemical changes during the maturation of three cacao genotypes were determined. Physiological follow-ups measuring fruit length and diameter were performed from 30 days after anthesis to fruit deterioration in the tree. RESULTS: Growth equations were obtained, establishing four maturity stages based on days after anthesis, and fruit length and diameter. Nineteen descriptors were used for the characterization, and through Pearson's correlation and principal component analysis (PCA), five descriptors were identified as representative of the maturity stages of the cacao fruit. PCA results and respiration measurements established that stage 3 presented the highest substrate availability for obtaining good fermentation and quality cacao. This stage showed values between 124 and 197 days after anthesis with lengths between 167.7 and 249.73 mm, and diameters between 64.4 and 95.8 mm, according to the locality. CONCLUSION: Three growth phases of the cacao fruits were established considering days after anthesis. Both the edaphoclimatic conditions and the cacao genotype characteristics influenced this determination. Stage 3 of fruit maturation shows the best physicochemical conditions for good fermentation. © 2021 Society of Chemical Industry.

Effect of soil characteristics on cadmium absorption and plant growth of Theobroma cacao L. seedlings.

BACKGROUND: Cadmium uptake by cacao plants can affect plant growth, consumer health and commercialisation. To develop mitigation strategies, it is essential to identify the soil characteristics that could influence this absorption. To determine the relationships between cadmium absorption and the soil characteristics of cacao areas, the responses at concentrations of 0, 2, 5, 10 and 20 µg g-1 of cadmium in three soils of these areas and an andisol were evaluated, using 120-day-old seedlings of four cultivars of Theobroma cacao L. RESULTS: In the present study, several relationships were found between chemical and physical soil characteristics and available cadmium, such as real and bulk densities, as well as contents of iron, sand, magnesium, potassium, sodium and copper. Additionally, moderate to strong correlations between potassium (r2  = -0.56) and real density (r2  = 0.42), with foliar cadmium, were found. Moreover, a differential deleterious effect on cacao growth in variables such as biomass was corroborated in cadmium concentrations from 5 µg g-1 in soils. There were no statistical differences between cultivars with respect to cadmium uptake or plant growth. Finally, a multiple linear regression model is proposed to estimate the foliar cadmium content (r2  = 0.878). CONCLUSION: Some soil characteristics such as density, as well as sand, clay, aluminium, potassium and iron contents, should be considered before establishing cacao crops to avoid cadmium accumulation. The correlation between potassium with foliar cadmium indicated that potassium could be significant in cadmium uptake mitigation strategies. The high correlation between available cadmium and foliar cadmium indicates that the quantification methodology developed using ethylenediaminetetraacetic acid extractant may be a useful diagnostic tool. © 2021 Society of Chemical Industry.

Plant metal concentrations in Theobroma cacao as affected by soil metal availability in different soil types.

Beans of cacao (Theobroma cacaoL.) are used to produce a variety of chocolate products. Bioaccumulation of metals at toxic levels through the consumption of contaminated products has been identified as a health concern in humans. Both metal diversity and concentration as well as their interactions in the soil influence essential and non-essential metal uptake in plants; but the effects of these on bioaccumulation of metals in cacao is not understood across diverse soil types. In this study eight metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) were investigated in 12 soil subgroups belonging to four soil orders across 15 locations in Trinidad, with the aim to investigate the effect of soil metal diversity and concentration on metal bioaccumulation in cacao. Soil metals were extracted using five methods (aqua regia, DTPA, Mehlich 3, nitric acid, and water). Cacao leaf metal concentrations were determined using the USEPA 3052 method. Metal extraction efficiency ranged between methods with aqua regia ≥ nitric acid > Mehlich 3 ≥ DTPA ≥ water across all metals. The soil extraction method that best predicted cacao leaf metal concentrations varied with the metal - Mehlich 3 or DTPA for Cd, Ni, Zn; aqua regia, Mehlich 3, or nitric acid for Pb, and water for Mn. A stepwise regression analysis showed that plant metal concentration can be predicted using soil physicochemical characteristics as well as the concentration of metals in the soil. The importance of soil type on cacao leaf metal bioaccumulation is discussed.

Genetic and environmental links between traits of cocoa beans and pods clarify the phenotyping processes to be implemented.

The average weight of cocoa beans is not generally taken into account during breeding processes, although it is a trait of interest. Several studies indicate that the weight of the beans has a high heritability in Theobroma cacao. However, the values obtained from different countries for the same clone often vary. In this study, we analyzed the effect of different factors on the weight of the beans. Apart from the clone effect, three main factors had an impact: i) the number of beans per pod: a good filling of the pod with beans tended to limit the weight of the beans, ii) the position of the beans in the pod: beans in the apical part of the pod were significantly lighter than the others and iii) the longer the duration of the fructification cycle the heavier the beans were (positive genetics correlation). These results lead us to propose protocols aimed at normalizing the phenotypic values of the genetic material. To obtain a reliable estimate of the bean weight, the following is proposed: either to use beans obtained from manual pollination to saturate the pods with beans, or to systematically use the number beans in the pods as a covariable.

ETAPOD: A forecast model for prediction of black pod disease outbreak in Nigeria.

Food poisoning and environmental pollution are products of excessive chemical usage in Agriculture. In Nigeria, cocoa farmers apply fungicides frequently to control black pod disease (BPD), this practice is life threatening and lethal to the environment. The development of a warning system to detect BPD outbreak can help minimize excessive usage of fungicide by farmers. 8 models (MRM1-MRM8) were developed and 5 (MRM1-MRM5) selected for optimization and performance check. MRM5 (ETAPOD) performed better than the other forecast models. ETAPOD had 100% performance rating for BPD prediction in Ekiti (2009, 2010, 2011 and 2015) with model efficiency of 95-100%. The performance of the model was rated 80% in 2010 and 2015 (Ondo) with model efficiency of 85-90%, 70% in 2011 (Osun) with model efficiency of 81-84%, 60% in 2010 (Ondo and Osun) and 2015 (Osun) with model efficiency of 75-80%, 40% in 2009 (Osun) with model efficiency of 65-69% and 0% 1n 2011 (Ondo) with model efficiency between 0 and 49%. ETAPOD is a simplified BPD detection device for the past, present and future.

Study of the physical and chemical changes during the maturation of three cocoa clones, EET8, CCN51, and ICS60.

BACKGROUND: Colombia is known for its production of fine and aromatic cocoa; however, the lack of homogeneity in the ripeness stage of cocoa fruit affects the final quality of cocoa beans. Therefore, the aim of this work was to identify parameters that can be use as indicators of ripeness in cocoa fruit in order to homogenize the characteristics of raw cocoa used in the production of cocoa-products industry. The parameters evaluated were fruit, seed and pod weight, firmness, color, polar and equatorial diameters of the fruit, seed moisture content, total titratable acidity, pH, and total soluble solids of pulp. RESULTS: Factors such as seed weight, firmness, diameters, total soluble solids, pH, and acidity were affected by the clone factor, whereas seed weight, pH, and total titratable acidity were affected by ripeness stage. CONCLUSION: Identification of indicators of ripeness for cocoa fruit is a complex task due to the influence of the clone on the evolution of the physicochemical characteristics of cocoa fruit during its maturation process. Thus, indicators must be developed for each clone, and at least two parameters among color, pH, and total titratable acidity should be used to determine the ripeness stage of cocoa fruit. © 2019 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Tree diversity and its ecological importance value in organic and conventional cocoa agroforests in Ghana.

Cocoa agroforestry systems have the potential to conserve biodiversity and provide environmental or ecological benefits at various nested scales ranging from the plot to ecoregion. While integrating organic practices into cocoa agroforestry may further enhance these potentials, empirical and robust data to support this claim is lacking, and mechanisms for biodiversity conservation and the provision of environmental and ecological benefits are poorly understood. A field study was conducted in the Eastern Region of Ghana to evaluate the potential of organic cocoa agroforests to conserve native floristic diversity in comparison with conventional cocoa agroforests. Shade tree species richness, Shannon, Simpson's reciprocal and Margalef diversity indices were estimated from 84 organic and conventional cocoa agroforestry plots. Species importance value index, a measure of how dominant a species is in a given ecosystem, and conservation status were used to evaluate the conservation potential of shade trees on studied cocoa farms. Organic farms recorded higher mean shade tree species richness (5.10 ± 0.38) compared to conventional farms (3.48 ± 0.39). Similarly, mean Shannon diversity index, Simpson's reciprocal diversity index and Margalef diversity index were significantly higher on organic farms compared to conventional farms. According to the importance value index, fruit and native shade tree species were the most important on both organic and conventional farms for all the cocoa age groups but more so on organic farms. Organic farms maintained 14 native tree species facing a conservation issue compared to 10 on conventional cocoa farms. The results suggest that diversified organic cocoa farms can serve as reservoirs of native tree species, including those currently facing conservation concerns thereby providing support and contributing to the conservation of tree species in the landscape.

Determination of optimum harvest maturity and non-destructive evaluation of pod development and maturity in cacao (Theobroma cacao L.) using a multiparametric fluorescence sensor.

BACKGROUND: A series of fluorescence indices (anthocyanin, flavonol, chlorophyll and nitrogen balance) were deployed to detect the pigments and colourless flavonoids in cacao pods of three commercial cacao (Theobroma cacao L.) genotypes (QH1003, KKM22 and MCBC1) using a fast and non-destructive multiparametric fluorescence sensor. The aim was to determine optimum harvest periods (either 4 or 5 months after pod emergence) of commercial cacao based on fluorescence indices of cacao development and bean quality. RESULTS: As pod developed, cacao exhibited a rise with the peak of flavonol occurring at months 4 and 5 after pod maturity was initiated while nitrogen balance showed a decreasing trend during maturity. Cacao pods contained high chlorophyll as they developed but chlorophyll content declined significantly on pods that ripened at month 5. CONCLUSION: Cacao pods harvested at months 4 and 5 can be considered as commercially-ready as the beans have developed good quality and comply with the Malaysian standard on cacao bean specification. Thus, cacao pods can be harvested earlier when they reach maturity at month 4 after pod emergence to avoid germinated beans and over fermentation in ripe pods harvested at month 5. © 2018 Society of Chemical Industry.

Effects of Maturity at Harvest and Fermentation Conditions on Bioactive Compounds of Cocoa Beans.

Cocoa beans and cocoa products contain considerable amounts of bioactive compounds. Harvesting cocoa fruit too early or too late may have effects on the phenolic and alkaloid concentrations of the cocoa powder. Fermentation, a primary processing used to transform cocoa beans to cocoa powder, may also influence the contents of bioactive compounds. In this study, proanthocyanidins, the major compounds in cocoa polyphenols, caffeine and theobromine of cocoa beans, were evaluated at different maturities at harvest, and with different fermentation durations, with and without the addition of a commercial enzyme, Pectinex® Ultra SP-L. The amounts of proanthocyanidins, caffeine and theobromine, and the antioxidant capacities of the unfermented cocoa beans increased as the fruits matured. The values ranged from 16.12-27.28 g catechin equivalents (CE)/100 g dry weight (DW); 99.66-173.61 mg/100 g DW; 556.39-948.84 mg/100 g DW; 23.23-26.32 mol Trolox equivalents (TE)/100 g DW, respectively. Prolonged fermentation with or without the addition of pectinase, from three to seven days, significantly reduced the amounts of these compounds present. Fermentation using the enzyme significantly reduced the proanthocyanidin content and antioxidant capacity of the cocoa powder, with the overall means decreasing from 8.93-4.93 g CE/100 g DW and from 15.81-12.95 g mol TE/100 g DW, respectively. Two-way ANOVA analyses showed that the proanthocyanidins, caffeine, theobromine contents and the antioxidant capacity of cocoa beans were strongly dependet to their stages of maturity, fermentation methods and fermentation duration.

Below- and aboveground production in cocoa monocultures and agroforestry systems.

Farmers expect yield reduction of cash crops like cocoa when growing in agroforestry systems compared to monocultures, due to competition for resources, e.g. nutrients and water. However, complementarities between species in the use of resources may improve resource use efficiency and result in higher system performance. Cocoa trees have a shallow rooting system while the rooting characteristics of the associated trees are mainly unknown. This work investigates fine root distribution and production in five cocoa production systems: two monocultures and two agroforestry systems under conventional and organic farming, and a successional agroforestry system. In the organic systems a perennial leguminous cover crop was planted and compost was added, while herbicides and chemical fertilizers were applied in the conventional ones. We measured cocoa fine root parameters in the top 10cm of soil and annual total fine root production at 0-25 and 25-50cm depth. We related the root data with both the aboveground performance (tree and herbaceous biomass), and the cocoa and system yields. Cocoa fine roots were homogenously distributed over the plot area. Around 80% of the total fine roots were located in the upper 25cm of soil. The total fine root production was 4-times higher in the agroforestry systems and the organic monoculture than in the conventional monoculture. The roots of the associated tree species were located in the same soil space as the cocoa roots and, in principle, competed for the same soil resources. The cocoa yield was lower in the agroforestry systems, but the additional crops generated a higher system yield and aboveground biomass than the conventional cocoa monocultures, implying effective resource exploitation. The leguminous cover crop in the organic monoculture competed with the cocoa trees for nutrients, which may explain the lower cocoa yield in this system in contrast with the conventional monoculture.

Photosynthesis limitations in cacao leaves under different agroforestry systems in the Colombian Amazon.

Cacao (Theobroma cacao L.) has traditionally been considered a crop that requires shade, and consequently it is implemented under agroforestry systems (AFs) in order to regulate the level of incident solar radiation. However, optimal shade levels for this tree crop may vary depending on the climate conditions of where it is grown. Here we analyzed the physiological performance of cacao under three different AFs in the Colombian Amazon that differed in solar radiation patterns: high (HPAR), medium (MPAR), or low (LPAR) mean daily incident radiation. The physiological performance was characterized using photosynthetic variables in leaves such as light- and CO2-response curves, chlorophyll a fluorescence parameters, and total chlorophyll and carotenoid contents, in conjunction with other leaf functional traits. Cacao trees exposed to HPAR showed an improved physiological performance as compared to those from the other two AFs. Compared to MPAR and LPAR, cacao trees in HPAR doubled the rate of net carbon assimilation and reached higher maximum rates of RuBisCO carboxylation and RuBP regeneration. Moreover, cacao trees in HPAR presented photoprotection mechanisms that avoided photoinhibition, which was accompanied by a greater non-photochemical quenching coefficient and biochemical and morphological adjustments (low chlorophyll but higher carotenoid contents and low specific leaf area) compared to cacao trees from the other AFs. Overall, our results show that, due to the high cloud cover in the Colombian Amazon, cacao plantations under conditions of sparse shade maximized their carbon use, showing an improved physiological performance as a result of higher photosynthetic rates and energy dissipation mechanisms. If the crop were managed with sparse shade, the paradigm that favors the cultivation of cacao under shade would be called into question in the Colombian Amazon and other regions with similar climatic conditions.

Glucocorticoid receptor-regulated TcLEC2 expression triggers somatic embryogenesis in Theobroma cacao leaf tissue.

Theobroma cacao, the source of cocoa, is a crop of particular importance in many developing countries. Availability of elite planting material is a limiting factor for increasing productivity of Theobroma cacao; therefore, the development of new strategies for clonal propagation is essential to improve farmers' incomes and to meet increasing global demand for cocoa. To develop a more efficient embryogenesis system for cacao, tissue was transformed with a transgene encoding a fusion of Leafy Cotyledon 2 (TcLEC2) to a glucocorticoid receptor domain (GR) to control nuclear localization of the protein. Upon application of the glucocorticoid dexamethasone (dex), downstream targets of LEC2 involved in seed-development were up-regulated and somatic embryos (SEs) were successfully regenerated from TcLEC2-GR transgenic flower and leaf tissue in large numbers. Immature SEs regenerated from TcLEC2-GR leaves were smaller in size than immature SEs from floral tissue, suggesting a different ontogenetic origin. Additionally, exposure of TcLEC2-GR floral explants to dex increased the number of SEs compared to floral explants from control, non-transgenic trees or from TcLEC2-GR floral explants not treated with dex. Testing different durations of exposure to dex indicated that a three-day treatment produced optimal embryo regeneration. Leaf derived SEs were successfully grown to maturity, converted into plants, and established in the greenhouse, demonstrating that these embryos are fully developmentally competent. In summary, we demonstrate that regulating TcLEC2 activity offers a powerful new strategy for optimizing somatic embryogenesis pipelines for cacao.

Soil organic matter and CO2 fluxes in small tropical watersheds under forest and cacao agroforestry.

Annual estimates of CO2 and dissolved carbon concentrations in the soil profile provide valuable insight into the dynamics of organic matter in soil and the effect of changes to vegetation cover. The aim of this study was to observe the spatial influence of litter decomposition in the first few centimeters of the soil for CO2 fluxes and to describe the processing of soil organic matter throughout the soil profile by comparing three small tropical watersheds. Data were collected biweekly for six months, from December 2015 to May 2016. CO2 was measured using an infrared gas analyzer in fixed chambers and the dissolved carbon of soil solution was analyzed in a TOC analyzer. No differences were found in the total soil CO2 fluxes (control flux treatments) between the three study areas. In both cacao agroforestry systems (managed and unmanaged), total CO2 fluxes were influenced by the decomposition of litter. CO2 emissions in the soil profile of the cacao agroforestry systems were highly variable, compared to the preserved forest, and highly dependent on the soil characteristics attributed to the type of vegetation cover. Although a definite pattern between the temperature and soil moisture was not identified, these parameters showed a strong relationship in controlling the release of CO2 between treatments. The organic and inorganic dissolved carbon patterns in the soil solution of the three areas revealed different responses of soil organic matter processing related to soil characteristics and vegetation. The results confirm the hypothesis that the top of soils (total CO2 fluxes) of both cacao agroforestry systems (managed and unmanaged) emits fluxes of CO2, which do not differ statistically from the preserved forest. However, depending on the soil characteristics, the cacao agroforestry system can result in an accumulation of CO2 and dissolved inorganic carbon in the soil profile that is prone to being transported by hydrological routes to groundwater and stream water.

Mechanical stress caused by wind on leaves of Theobroma cacao: Photosynthetic, molecular, antioxidative and ultrastructural responses.

Theobroma cacao is cultivated in the shade, in a so-called 'Cabruca' system, in intercropped with Erithryna or other tree species of economic value, and in full sun as a monoculture in irrigated or chemically-irrigated systems. Since it is a species quite intolerant to wind, it is practically impossible to implant cacao crops under full exposure to the sun, or in areas of frequent winds, without the protection of windbreaks, using arboreal species around the area of culture in the form of box. Wind can cause mechanical stimuli in plants, affecting their growth and development. The objective of this work was to evaluate the photosynthetic changes in mature leaves and the molecular, biochemical and ultrastructural changes in young and mature leaves of the CCN 51 cloned genotype of T. cacao subjected to intermittent (IW) and constant (CW) wind, with velocities of 2.5, 3.5 and 4.5 m s-1, during 3, 6 and 12 h of exposure. It was verified that CW and IW, considering different exposure times, interfered directly in stomatal conductance (gs), transpiration (E) and water use efficiency (WUE), causing a reduction of the photosynthetic rate (A) in mature leaves. In addition, the pulvinus and blade of young and mature leaves, exposed to IW and CW with different exposure times (3 and 12 h), showed marked macroscopic and microscopic mechanical injuries resulting from the constant leaf movement. At both speeds, there was rupture of the cell nuclear membrane in pulvinus and the mesophyll tissues, mainly in the young leaves. On the other hand, in young and mature leaves exposed to CW and IW at different speeds and exposure times, there was lipid peroxidation, increased activity of guaiacol (GPX) and ascorbate (APX) peroxidases in most treatments; and altered expression of transcripts of psba and psbo genes related to the phothosynthetic apparatus and Cu-Zn-sod and per genes related to antioxidative enzymes at the rate of 4.5 m s-1. Younger leaves were more intolerant to mechanical stress caused by the wind, since presented greater macro and microscopic damages and, consequently, greater molecular, biochemical and ultrastructural changes. High wind speeds can seriously compromise the development of young leaves of T. cacao plants and affect their productivity.

Potentials of cocoa pod husk-based compost on Phytophthora pod rot disease suppression, soil fertility, and Theobroma cacao L. growth.

Cocoa black pod disease caused by Phytophthora megakarya and reduced soil fertility are major constraints to cocoa production resulting in high yield losses. In the absence of effective control measures and constraints related to the use of chemical fungicides and fertilizers, there is a need to develop additional and sustainable disease and fertilization management strategies. With the lack of studies related to the use of compost in cocoa cultivation, the present study aims to evaluate the potential of cocoa pod husk (CPH)-based compost as a soil amendment to reduce the severity of cocoa black pod disease and enhance plant growth. In vitro antagonism test showed that compost water extracts (CWE) reduced mycelial growth with inhibition rate reaching 100% associated with microorganisms. Disease score of cocoa plantlets grown on compost-amended soils significantly reduced compared to plantlets grown on non-amended soil (control). All compost rates tested significantly increased populations of actinomycetes and fungi and biological activity in the soil. Compost application increased soil pH and majority of the essential elements but decreased Al content, which is toxic to cocoa growth in acidic soils. Soil application of compost at the dose of 20% (v/v) significantly increased stem length and number of leaves compared to the control. This study shows that CPH-based compost can not only improve soil fertility and cocoa growth but also reduce cocoa black pod disease severity by direct effects on inoculums level in the soil and by inducing resistance in the plant.