Overview
This is a pot experiment evaluating cadmium uptake, translocation, and tolerance in nine cacao (Theobroma cacao L.) rootstock genotypes, not a study of finished-food cadmium concentrations. The experiment was conducted under greenhouse conditions at the Agrosavia “La Suiza” Research Center in Santander, Colombia. Juvenile plants were exposed to 0, 6, and 12 mg·kg−1 CdCl2 in substrate for up to 90 days, and cadmium content was measured in roots, stems, and leaves by atomic absorption spectrophotometry. The paper reports cadmium concentration per tissue, translocation factors, tolerance indices, and cadmium allocation dynamics across plant organs over time.
The central finding is that PA46 and IMC67 genotypes accumulated the lowest cadmium in shoots at both exposure levels, making them candidates for rootstock selection in cadmium mitigation strategies. EET61 was the highest shoot accumulator. All nine genotypes were classified as highly tolerant to cadmium (tolerance index at or above 60% under the classification of Lux et al. 2004), though their physiological strategies for coping with cadmium differed substantially. No fruit or bean cadmium data were measured; the authors note a positive correlation between shoot and bean cadmium reported in prior literature.
Key numbers
Shoot cadmium (Cd) concentration after 90 days of exposure (approximate values from Figure 3):
At 6 mg·kg−1 CdCl2, PA46, IMC67, PA121, and IMC60 had the lowest shoot Cd, while EET61 was the highest accumulator. The abstract reports EET61 shoots reached approximately 270 mg·kg DW−1 and PA46 approximately 20 mg·kg DW−1 at 12 mg·kg−1 exposure.
At 12 mg·kg−1 CdCl2, PA46, IMC67, and EET62 had the lowest shoot Cd content, followed by SCC86, PA121, IMC60, and SCC85; PA150 was next; EET61 was again the highest.
Total Cd per plant after 90 days at 12 mg·kg−1 (from Figure S5):
- PA46: 0.30 mg plant−1 (lowest)
- IMC67: 0.44 mg plant−1
- EET61: 2.53 mg plant−1 (highest), with 50% allocated to leaves
Tolerance index (TI, averaged over 90 days):
EET62 was the most tolerant genotype at both Cd levels, with significant differences relative to IMC67, PA150, PA46, and SCC86 at 6 mg·kg−1. The lowest TI value observed was approximately 0.85 for EET61 at 12 mg·kg−1, still above the 60% threshold for “highly tolerant” classification. All genotypes met the TI at or above 60% criterion at both exposure levels.
Cadmium allocation dynamics at 12 mg·kg−1:
Most genotypes allocated cadmium predominantly to roots during the first 30 days. By 90 days, allocation shifted to shoots in all genotypes. EET61 had 98% of cadmium in shoot tissues (leaves and stems) at 90 days. PA46, the genotype with the highest root allocation at 90 days, still had only 20% of total plant cadmium in roots and 80% in shoots.
Genotype ranking for Cd mitigation potential (from Discussion):
At approximately 6 mg Cd kg−1 substrate: PA46, IMC67, IMC60, PA121, SCC86, SCC85, PA150, EET62, EET61 (best to worst).
At approximately 12 mg Cd kg−1 substrate: PA46, IMC67, EET62, SCC86, PA121, IMC60, SCC85, PA150, EET61 (best to worst).
Evidence fitness
Rated EF-4 (“Context only”). This study measured cadmium in vegetative tissues of juvenile cacao rootstock genotypes under greenhouse pot conditions with CdCl2-spiked substrate. It did not measure cadmium in cacao beans, nibs, cocoa powder, chocolate, or any finished food matrix. The results characterize genotypic variation in plant-level cadmium uptake and translocation, which is relevant context for understanding rootstock-based mitigation strategies, but the data cannot be used to populate or adjust contamination profile values on finished-food ingredient or product pages. The plants were juveniles without fruit; the authors themselves note that field validation in adult plants is needed.
Methods
Instrument: Atomic absorption spectrophotometry.
Digestion: Nitric-perchloric acid (3:1, v/v).
Experimental design: Completely randomized block design, factorial 9 (genotypes) x 3 (Cd levels: 0, 6, 12 mg·kg−1 CdCl2) x 3 (destructive harvest times: 30, 60, 90 days after exposure). Twenty independent plants per experimental unit; nine replicates selected randomly for growth measurements (n = 9); cadmium determination used composite samples combining the nine replicates into three (n = 3).
Growth conditions: Greenhouse at Agrosavia “La Suiza” Research Center, Rionegro, Santander, Colombia (7 22’12” N, 73 10’39” W, 530 m elevation). Average temperature 25 +/- 4 C. Polyethylene pots (2.8 L) with soil/sand/compost substrate (3:1:0.5). Plants under 65% shade by nursery mesh.
Statistical analysis: ANOVA on ranks (p at or below 0.05), followed by Tukey comparison test (p < 0.05) or Student’s t-test.
Translocation factor (TF): Shoot Cd content (mg·kg−1) / Root Cd content (mg·kg−1).
Tolerance index (TI): Cd-exposed whole plant dry weight / control whole plant dry weight x 100.
Detection limits and method LOQ: Not reported.
Implications
This paper provides context for rootstock selection and breeding pathways as a pre-harvest mitigation strategy against cadmium bioaccumulation in cacao. It does not provide finished-food concentration data and should not be used to set or adjust contamination profile values on the cocoa ingredient page or any product-category page.
For certification purposes, the study demonstrates that genotypic variation in cadmium translocation from roots to shoots is large (approximately 13-fold range between PA46 and EET61 at 12 mg·kg−1) and that this variation is dose-dependent. This supports the broader case that rootstock selection is a viable component of supply-chain cadmium mitigation, alongside soil amendments, origin screening, and post-harvest processing strategies.
For courses, the study is a useful illustration of phytostabilization versus tolerance as distinct physiological strategies, and of the practical limitation that long-term root compartmentalization of cadmium did not persist in any of the nine genotypes tested. The finding that cadmium allocation shifted from roots to shoots over 90 days in all genotypes, even those with low total uptake, is relevant to setting realistic expectations for rootstock-based mitigation programs.
Provenance notes
Open access under CC BY 4.0. Published in Plants (MDPI), August 2023. Research conducted at AGROSAVIA (Colombian Agricultural Research Corporation) and University of Cordoba, Colombia. Funded by Sistema General de Regalias and the BOTANICA Research Group, University of Cordoba.
Related evidence
- Cadmium
- Cocoa
- mitigation/cocoa-cadmium
- ClimaLOCA project: Fostering innovations for cadmium reduction in cocoa beans in Latin America
- Mitigation of Cadmium Accumulation in Cocoa Beans Using Arbuscular Mycorrhizal Fungi, Biochar and Callisia repens
Update history
The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git.
| Commit | Date | Change | Description |
|---|---|---|---|
| 74bd6a9746 | 2026-11-10 | major | 2 sources added; 7 sections added; narrative text revised |