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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Sustainable Perennial Crops Laboratory » Research » Research Project #426238

Research Project: Sustainable Production Systems for Cacao

Location: Sustainable Perennial Crops Laboratory

2018 Annual Report

The overall goal of this project is to develop sustainable management systems to improve the productivity and sustainability of cacao (Theobroma cacao L) cultivation. To accomplish this goal the following objectives will be addressed Objective 1: Identify cacao genotypes with superior ability for establishment under conditions of environmental stress. [NP 301, C1, PS 1A] Sub-objective 1A: Evaluate and identify cacao genotypes with superior tolerance to soil acidity. Sub-objective 1B: Determine key physiological and growth responses of selected cacao genotypes under different levels of irradiance (shade). Sub-objective 1C: Evaluate and identify selected cacao genotypes with superior drought tolerance. Objective 2: Characterize and manage soil nutritional components essential for optimal cacao yields. [NP 305, C1, PS 1C] Sub-objective 2A: Determine the residual effects of cover crops with and without NPK fertilizers on production potentials and bean quality. Sub-objective 2B: Determine the effectiveness of controlled release fertilizer formulations on improving growth, production, and cocoa bean quality of selected cacao genotypes grown in specific soil types. Sub-objective 2C: Determine optimum concentrations and nutrient use efficiencies of macro and micro-nutrients in selected cacao genotypes. Objective 3: Develop environmentally sustainable cacao management systems that improve soil quality and yield. [NP 305, C1, PS1C] Sub-objective 3A: Integrate improved canopy management, phytosanitation, and other management practices into cacao field experiments to evaluate their combined effect on yield. Sub-objective 3B: Develop an improved cacao rejuvenation system that integrates improved management practices and evaluates its effect on cacao yield.

The major emphasis of this project is to identify cacao genotypes tolerant to abiotic stresses (drought, infertile acidic soils, and high/low irradiance) and develop sustainable management systems to improve their productivity and bean quality. The residual effects of cover crop cultivation and improved management systems (agroforestry planting, high density planting, fertilization, sanitary and phyto-sanitary practices) on the changes of soil quality parameters (physical, chemical, biological) and bean yield and quality will also be determined. Nutrient use efficiency of macro-micronutrients of elite cacao genotypes and cover crops at various abiotic stresses and management systems will be evaluated. Enhanced nutrient use efficiency and sustainable high productivity of cacao will be achieved through improved management practices. To achieve these objectives we have established collaborative research programs under specific cooperative agreements with government and non-government organizations (NGO) and national and international agricultural universities in cacao growing regions of Peru, Brazil, and Ecuador, and the University of Florida at Fort Pierce as well as the USDA ARS in Puerto Rico to establish controlled studies in greenhouses and large scale field trials. University of Reading (UR), UK will be collaborating on abiotic stress assessment. Cacao genotypes with superior ability for establishment under abiotic stresses will be identified and incorporated in cacao improvement programs. Improved management systems will be developed, based on the results of this research, to enhance cacao yield potentials and bean quality and further improve soil fertility and halt the further soil degradation.

Progress Report
This is the final report for Project 8042-21000-278-00D, which was terminated as directed by the January 31, 2018 PDRAM and this project has been replaced by the new NP301 Project 8042-21000-281-00D. Substantial progress was made over the four-year period on all three objectives and their sub objectives. Objective 1 and Subobjectives 1A, B, and C, fall under National Program 301, Plant Genetic Resources, Genomic, and Genetic Improvement Component 1. Crop genetic improvement and Objective 2 and Sub objectives 2A, B and C and Objective 3 and Subobjectives 3A and B, fall under National Program 305 Crop Production, Component 1. Integrated Sustainable Crop Production Systems. Collaborative research was undertaken with scientists from the State University of Santa Cruz (UESC), and Cacao Research Institute (CEPLAC/CEPEC) Bahia, Brazil in a funded agreement to assess the cacao genotypic response to abiotic stresses (drought, light, elemental toxicities and deficiencies) and to evaluate the effects of the “cabruca” cacao agroforestry management systems on soil quality factors. Significant progress was made in the evaluation of cacao genotypes and their response to toxic levels of cadmium. Growth, physiology and molecular responses, and leaf anthocyanin contents of cacao in response to light was also evaluated, as well as the effect of drought and flooding responses of different cacao genotypes (Objective 1A, B, C). Drought affects the growth and development of roots, and shoots and root volume was identified as the growth variable most influenced by drought (Objective 1C). Drought also reduced biomass accumulations and leaf area. Flooding reduced photo synthesises and macro-micronutrient content and flooding susceptible clones showed lower chlorophyll content and increased activity of peroxidases and polyphenol oxidases. At Beltsville, Maryland, significant progress was made in the evaluation of cacao genotypes and how they respond to deficit and adequate levels of macro-micronutrients (Sub-objective 1A, B and C). Intra specific differences were observed in cacao genotypes for use efficiency of nitrogen, potassium, iron, zinc and copper. Toxic levels of cadmium in the growth medium reduced photosynthesis, and led to irreversible damage to cellular and root ultrastructure and consequently affected the growth and development of cacao (Objective 1A, and 2C). In Bahia, Brazil 15 long-term cacao agroforestry management systems were evaluated for their effects on soil quality parameters. Cacao agroforestry systems accumulated high organic carbon in the soil, suggesting a potential benefit in mitigation of greenhouse gases. In highly weathered soils under agroforestry system, the main mechanisms of carbon stabilization appear to be physical protection within macro aggregates thereby minimizing the impact of converting forest to cacao agroforestry systems. Agroforestry based cacao cropping systems affected the mineral composition of dry cacao beans. Variations in the mineral content of manganese, iron, zinc, copper, cadmium and barium in cacao beans were influenced by the cropping sites and in some sites, cadmium contents were higher than the limit set by the European Union (Objective 2C and Objective 3A). Collaborative research was undertaken with scientists from the Tropical Crop Research Institute (ICT) in Tarapoto, Peru and National University of Agraria La Molina (UNALM) Lima, Peru under a funded agreement to develop sustainable production systems for tropical tree crops and assess cacao germplasm to improve cacao sustainability under various abiotic stresses. At ICT Tarapoto, Peru a clonal garden has been established to evaluate wild cacao accessions collected from the Amazon River basins of Peru and Common Fund for Commodities (CFC) clones from the University of Reading, United Kingdom. Substantial progress was made toward Objectives 1.A, B, and C to assess the performance of cacao varieties or genotypes collected from various Peruvian river basins, along with national and international cacao genotypes to abiotic stresses (drought, and soil acidity). Intraspecific differences in wild and domesticated cacao were observed in response to drought and light quality. Various plant traits such as growth, and physiology were recorded and shoot samples were analyzed for macro-micronutrient content to evaluate nutrient use efficiency of cacao accessions under abiotic stresses. In another study, leaves and beans of cacao were collected from 70 farms in northern and central regions of Peru that had been exposed to a varying range of heavy metal concentrations cadmium, chromium, copper, iron, manganese, nickel, lead and zinc. The results show a large variation in the accumulations of heavy metals. From these observations, it appears that it may be possible to select for low heavy metal accumulating cacao genotypes, which would be useful in crop improvement programs. Furthermore, heavy metal content of soils from northern, central and southern cacao growing regions of Peru were evaluated with soils from the northern region having toxic levels of cadmium and it was observed that in general soils pH, and percent clay and magnesium content had a high degree of correlation to soil heavy metal content. Two long-term cacao management studies were established in ICT Tarapoto, Peru in an area originally inhabited by 30 years old native secondary forest (SF). The two agroforestry systems adapted were: improved natural agroforestry system (INAS) where trees without economic value were selectively removed to provide 50% shade and improved traditional agroforestry system (ITAS) where all native trees were cut and burnt in the location. Yield data were collected to assess the yielding ability of various cacao genotypes grown under these two management systems and in areas previously grown with cover crops (Objective 2A, Objective 3A). The overall improvement of soil organic matter (SOM) and soil nutrient status was much higher in the ITAS than INAS. The levels of physical and chemical properties of soil under cacao genotypes showed a marked difference in both systems. In collaborations with ARS scientists in Beltsville, Maryland, the effects of long-term cacao genotypes management and the influence of cover crops on soil biological quality factors were analyzed. (Objective 2A, Objective 3A) Soil microbial community structure under cacao was affected by soil chemistry, agroforestry management system, and cover cropping. The success of sustainable cacao production systems in the Peruvian Amazon areas is dependent on the proper management of the physical and chemical properties of these soils. Long-term field studies continue to evaluate cacao genotypic performance for growth, diseases, insect intensities, and yield under different agroforestry systems. Improved canopy management and phytosanitory practices have been implemented on these field experiments (Objective 3A). Significant progress was made in collaborative research undertaken with ARS researchers in Mayaguez, Puerto Rico to assess soil acidity complexes on the performance of different cacao genotypes (Objective 1A). Intra specific differences were observed in cacao accessions for tolerance to soil acidity complexes based on plant growth traits and soil acidity tolerance indexes. Efforts are underway to assess these various soil acidity tolerant cacao accessions for drought. Considerable progress was also made through collaborative research undertaken with scientists from the University of Florida Indian River Research and Education Center (IRREC) Fort Pierce, Florida, under a funded agreement to evaluate nutrient use efficiency of cacao genotypes subjected to abiotic stresses (Objective 1A, B, C). Progress has been made in the understanding of changes in the elemental composition of macro (nitrogen, phosphorus, potassium, calcium, magnesium) and micronutrients (boron, copper, manganese, iron, zinc) of different cacao genotypes subjected to abiotic stresses.

1. Heavy metal accumulations in cacao (Theobroma cacao L.) leaves and cacao beans in the main cacao growing regions of Peru. Cacao in South America is grown on soils that may have high levels of cadmium and cacao plants are efficient in transporting soil cadmium to aerial parts and into cacao beans. Peru is the tenth leading exporters of cacao beans in the world and the accumulation of heavy metals in cacao beans significantly reduces bean quality, which reduces the market value of this crop, drastically affecting the economic well-being of resource poor farmers. An ARS researcher in Beltsville, Maryland, and international collaborators measured the range of heavy metals concentrations (Cadmium, Chromium, Copper, Iron, Manganese, Nickel, Lead, Zinc) in leaves and beans of cacao grown on 70 farms in northern and central regions of Peru. High levels of Cadmium were found in bean and leaf samples of cacao grown in the Amazonas, Piura, San Martin, and Tumbes, regions of Peru. Soil chemical properties and the levels of heavy metals accumulated in this crop are being used to identify methods to monitor and reduce the toxic levels of heavy metals in cacao beans. This information will help Peruvian scientists and farmers avoid areas that are high in cadmium and to screen for cacao germplasm with reduced uptake thereby promoting sustainable cacao production and protecting the market value of Peruvian cacao in the international cacao trade.

2. Impact of drought on morphological, physiological and nutrient use efficiency of elite Cacao genotypes from Bahia-Brazil, Tarapoto-Peru and Puerto Rico-U.S. Worldwide, drought is one of the most limiting factors for cacao growth, development, nutrition and production; further, quantity and distribution of rainfall, have been a major cause of variation in cacao productivity and sustainability in many cacao growing regions. Very little is known about cacao's ability to adapt to short or long duration drought and most of the current cacao germplasm maintained in cacao growing regions has not been screened for drought tolerance. An ARS researcher in Beltsville, Maryland, and international collaborators identified morphological, physiological and nutrient use efficiency of cacao genotypes from Bahia-Brazil, Tarapoto-Peru and Puerto Rico in greenhouses and growth chambers that were effective in separation cacao genotypes with various degrees of drought tolerance. Root volume was identified as the growth variable most influenced by drought. Understanding plant growth, morphology, physiology and nutrient use efficiency influenced by drought can be used to identify cacao genotypes tolerant to drought. These findings will lead to the utilization of drought tolerant cacao genotypes to breed superior cacao cultivars that are resistant to drought thereby enhancing the cacao sustainability in drought prone regions of the world.

Review Publications
Santos, E.A., Almeida, A.F., Branco, M.C., Santos, I.C., Ahnert, D., Baligar, V.C., Valle, R.R. 2018. Path analysis of phenotypic traits in young cacao plants under drought conditions. PLoS One. 13(2):1-16.
Arevalo-Hernandez, C.O., Conceicao, P.F., Souza, J.O., Queiroz, P.A., Baligar, V.C. 2017. Variability and correlation of physical attributes of soils cultivated with cacao trees in two climate zones in southern Bahia, Brazil. Agroforestry Systems.
Romaria, A., Pereira, L.S., Pereira, L.S., Mangabeira, P.A., Souza, J.O., Ahnert, D., Baligar, V.C. 2017. Photosynthetic, antioxidative, molecular and ultrastructural responses of young cacao plants to Cd toxicity in the soil. Ecotoxicology and Environmental Safety.
Arevalo-Gardini, E., Arevalo-Hernandez, C., Baligar, V.C., He, Z. 2017. Heavy metal accumulations in cacao (Theobroma cacao L.) leaves and cocoa beans grown at three main cacao growing regions of Peru. Science of the Total Environment. 17(2):410-428.
He, S., Yang, X., He, Z., Baligar, V.C. 2017. Morphological and physiological responses of plants to cadmium toxicity: A review. Pedosphere. 27(3):421–438.
Buyer, J.S., Baligar, V.C., He, Z., Gardini, E.A. 2017. Soil microbial communities under cacao agroforestry and cover crop systems in Peru. Applied Soil Ecology. 120:273-280.