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Agronomy
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Advances in Understanding Physiological Processes of the Cacao Tree
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Advances in Understanding Physiological Processes of the Cacao Tree

A special issue of Agronomy (ISSN 2073-4395). This special issue belongs to the section "Soil and Plant Nutrition".

Deadline for manuscript submissions: closed (31 March 2022) | Viewed by 17766

Special Issue Editor

Dr. Andrew Daymond

E-Mail Website
Guest Editor
School of Agriculture, Policy and Development, the University of Reading, Whiteknights, Reading RG66AR, UK
Interests: cacao physiology; climate change; photosynthesis; soil amendments; on-farm yield variation; characterisation of germplasm

Special Issue Information

Dear Colleagues,

Cacao is an economically important crop that is cultivated throughout the humid tropics, providing the essential raw ingredient for the chocolate industry. Cacao is predominantly cultivated by smallholder farmers, and yields on many cacao farms remain relatively low. It can be cultivated as a monoculture or within agroforestry systems. Periods of abiotic stresses encountered in many growing regions, such as drought, flooding, and excessive temperatures, can impact on establishment, yield, and the quality of the crop. Such stresses are being exacerbated by climate change.

Improving our understanding of physiological processes of the cacao tree is pivotal to improving crop yields through breeding and crop management and in devising strategies to adapt to climate change. In this Special Issue, we explore recent advances in our understanding of physiological processes of the cacao tree. We particularly welcome papers covering the following themes: 1) cacao responses to abiotic stresses (including multiple stresses and simulated climate change), 2) genotype–environment interactions, 3) cacao nutrition, 4) cacao physiology within shaded/ agroforestry systems.

Dr. Andrew Daymond
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Agronomy is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • cacao physiology
  • temperature
  • water deficit
  • flooding
  • nutrition
  • climate change
  • agroforestry

Published Papers (5 papers)

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Research

22 pages, 2064 KiB  
Article
Growth, Physiological, Nutrient-Uptake-Efficiency and Shade-Tolerance Responses of Cacao Genotypes under Different Shades
by Enrique Arévalo-Gardini, Abel Farfán, Fiorella Barraza, César O. Arévalo-Hernández, Luis B. Zúñiga-Cernades, Julio Alegre and Virupax C. Baligar
Agronomy 2021, 11(8), 1536; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy11081536 - 30 Jul 2021
Cited by 5 | Viewed by 3134
Abstract
Cacao is an understory plant cultivated in full-sun monocultures, multistrata agroforestry systems, where cacao trees are planted together with fruit, timber, firewood, and leguminous trees, or within thinned native forests. In agroforestry systems of cultivation, cacao is subjected to excess shade due to [...] Read more.
Cacao is an understory plant cultivated in full-sun monocultures, multistrata agroforestry systems, where cacao trees are planted together with fruit, timber, firewood, and leguminous trees, or within thinned native forests. In agroforestry systems of cultivation, cacao is subjected to excess shade due to high density, excess growth, and the unmanaged pruning of shade trees. Cacao is tolerant to shade, and the maximum photosynthetic rate occurs at an irradiance of around 400 μmol m−2 s−1. However, excess shade further reduces the irradiance, which is detrimental to photosynthesis and growth functions. Intra-specific variation is known to exist in cacao for the required saturation irradiance. A greenhouse study was implemented with 58 cacao genotypes selected from four geographically diverse groups: (i) wild cacao from river basins of the Peruvian Amazon (PWC); (ii) Peruvian farmers’ collection (PFC); (iii) Brazilian cacao collection (BCC); and (iv) national and international cacao collections (NIC). All of the cacao genotypes were subjected to 50% and 80% shade where photosynthetic photon flux density (PPFD) was 1000 and 400 μmol m−2 s−1, respectively. Intra-specific variations were observed for growth, physiological and nutritional traits, and tolerance to shade. Cacao genotypes tolerant to shade were: UNG-77 and UGU-130 from PWC; ICT-2173, ICT-2142, ICT-2172, ICT-1506, ICT-1087, and ICT-2171 from PFC; PH-21, CA-14, PH-990, and PH-144 from BCC; and ICS-1, ICS-39, UF-613, and POUND-12 from NIC. Genotypes that tolerate excess shade may be useful plant types for maintaining productivity and sustainability in agroforestry systems of cacao management. Full article
(This article belongs to the Special Issue Advances in Understanding Physiological Processes of the Cacao Tree)
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14 pages, 4258 KiB  
Article
How Do Different Cocoa Genotypes Deal with Increased Radiation? An Analysis of Water Relation, Diffusive and Biochemical Components at the Leaf Level
by Juan Carlos Suárez, Cristian Gelpud, Jhon Eduar Noriega and Fausto Andrés Ortiz-Morea
Agronomy 2021, 11(7), 1422; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy11071422 - 16 Jul 2021
Cited by 4 | Viewed by 2923
Abstract
The cultivation of cocoa (Theobroma cacao L.) is traditionally managed under shade because of its photosynthetic characteristics; however, its behavior can vary according to the genotype and environmental conditions where it is grown. In this sense, here, we explore the possible mechanisms [...] Read more.
The cultivation of cocoa (Theobroma cacao L.) is traditionally managed under shade because of its photosynthetic characteristics; however, its behavior can vary according to the genotype and environmental conditions where it is grown. In this sense, here, we explore the possible mechanisms of protection against radiation stress and how these mechanisms are affected by variation between cocoa genotypes. Therefore, we evaluate the effect of the radiation level (HPAR, 2100 ± 46 mol m−2 s−1; MPAR, 1150 ± 42 mol m−2 s−1; LPAR, 636 ± 40 mol m−2 s−1) on the water status and gas exchange in plants of different cocoa genotypes (CCN-51, ICS-1, ICS-95, LUKER-40 and LUKER-50), and the occurrence of photoinhibition of PSII (as a marker of photodamage), followed by a characterization of the protection mechanisms, including the dynamics of photosynthetic pigments and enzymatic and non-enzymatic antioxidant systems. We found significant changes in the specific leaf area (SLA) and the water potential of the leaf (ΨL) due to the level of radiation, affecting the maximum quantum yield of PSII (Fv/Fm), which generated dynamic photoinhibition processes (PIDyn). Cocoa genotypes showed the lowest Light-saturated maximum net carbon assimilation rate (Amax) in HPAR. Moreover, the maximum carboxylation rate (Vcmax) was negatively affected in HPAR for most cocoa genotypes, indicating less RuBisCO activity except for the ICS-95 genotype. The ICS-95 showed the highest values of Vcmax and maximum rate of regeneration of ribulose-1,5-bisphosphate (RuBP) controlled by electron transport (Jmax) under HPAR. Hence, our results show that some genotypes were acclimated to full sun conditions, which translated into greater carbon use efficiency due to the maximization of photosynthetic rates accompanied by energy dissipation mechanisms. Full article
(This article belongs to the Special Issue Advances in Understanding Physiological Processes of the Cacao Tree)
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15 pages, 2494 KiB  
Article
Climate Change Impacts on Cacao: Genotypic Variation in Responses of Mature Cacao to Elevated CO2 and Water Deficit
by Fiona Lahive, Liam R. Handley, Paul Hadley and Andrew J. Daymond
Agronomy 2021, 11(5), 818; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy11050818 - 22 Apr 2021
Cited by 12 | Viewed by 3179
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Advances in Understanding Physiological Processes of the Cacao Tree)
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19 pages, 2765 KiB  
Article
Potassium Application Positively Modulates Physiological Responses of Cocoa Seedlings to Drought Stress
by Esther Anokye, Samuel T. Lowor, Jerome A. Dogbatse and Francis K. Padi
Agronomy 2021, 11(3), 563; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy11030563 - 17 Mar 2021
Cited by 18 | Viewed by 4092
Abstract
With increasing frequency and intensity of dry spells in the cocoa production zones of West Africa, strategies for mitigating impact of water stress on cocoa seedling survival are urgently required. We investigated the effects of applied potassium on biomass accumulation, physiological processes and [...] Read more.
With increasing frequency and intensity of dry spells in the cocoa production zones of West Africa, strategies for mitigating impact of water stress on cocoa seedling survival are urgently required. We investigated the effects of applied potassium on biomass accumulation, physiological processes and survival of cocoa varieties subjected to water stress in pot experiments in a gauzehouse facility. Four levels of potassium (0, 1, 2, or 3 g/plant as muriate of potash) were used. Soil water stress reduced plant biomass accumulation (shoot and roots), relative water content (RWC), chlorophyll content and fluorescence. Leaf phenol and proline contents were increased under water stress. Additionally, compared to the well-watered conditions, soils under water stress treatments had higher contents of exchangeable potassium and available phosphorus at the end of the experimental period. Potassium applied under well-watered conditions reduced leaf chlorophyll content and fluorescence and increased leaf electrolyte leakage, but improved the growth and integrity of physiological functions under soil water stress. Potassium addition increased biomass partitioning to roots, improved RWC and leaf membrane stability, and significantly improved cocoa seedling survival under water stress. Under water stress, the variety with the highest seedling mortality accumulated the highest contents of phenol and proline. A significant effect of variety on plant physiological functions was observed. Generally, varieties with PA 7 parentage had higher biomass partitioning to roots and better seedling survival under soil moisture stress. Proportion of biomass partitioned to roots, RWC, chlorophyll fluorescence and leaf electrolyte leakage appear to be the most reliable indicators of cocoa seedling tolerance to drought. Full article
(This article belongs to the Special Issue Advances in Understanding Physiological Processes of the Cacao Tree)
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21 pages, 353 KiB  
Article
The Impact of Carbon Dioxide Concentrations and Low to Adequate Photosynthetic Photon Flux Density on Growth, Physiology and Nutrient Use Efficiency of Juvenile Cacao Genotypes
by Virupax C. Baligar, Marshall K. Elson, Alex-Alan F. Almeida, Quintino R. de Araujo, Dario Ahnert and Zhenli He
Agronomy 2021, 11(2), 397; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy11020397 - 23 Feb 2021
Cited by 11 | Viewed by 2798
Abstract
Cacao (Theobroma cacao L.) was grown as an understory tree in agroforestry systems where it received inadequate to adequate levels of photosynthetic photon flux density (PPFD). As atmospheric carbon dioxide steadily increased, it was unclear what impact this would have on cacao [...] Read more.
Cacao (Theobroma cacao L.) was grown as an understory tree in agroforestry systems where it received inadequate to adequate levels of photosynthetic photon flux density (PPFD). As atmospheric carbon dioxide steadily increased, it was unclear what impact this would have on cacao growth and development at low PPFD. This research evaluated the effects of ambient and elevated levels carbon dioxide under inadequate to adequate levels of PPFD on growth, physiological and nutrient use efficiency traits of seven genetically contrasting juvenile cacao genotypes. Growth parameters (total and root dry weight, root length, stem height, leaf area, relative growth rate and net assimilation rates increased, and specific leaf area decreased significantly in response to increasing carbon dioxide and PPFD. Increasing carbon dioxide and PPFD levels significantly increased net photosynthesis and water-use efficiency traits but significantly reduced stomatal conductance and transpiration. With few exceptions, increasing carbon dioxide and PPFD reduced macro–micro nutrient concentrations but increased uptake, influx, transport and nutrient use efficiency in all cacao genotypes. Irrespective of levels of carbon dioxide and PPFD, intraspecific differences were observed for growth, physiology and nutrient use efficiency of cacao genotypes. Full article
(This article belongs to the Special Issue Advances in Understanding Physiological Processes of the Cacao Tree)
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