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Project properties |
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| Title | Quantifying the role of root exudates in the cadmium uptake by cacao in Latin America |
| Group | Soil Biology |
| Project type | thesis |
| Credits | 24-39 |
| Supervisor(s) | Wietse Wiersma, Marie Zwetsloot, Mirjam Pulleman |
| Examiner(s) | prof.dr. Rachel Creamer |
| Contact info | wietse.wiersma@wur.nl |
| Begin date | 2022/09/01 |
| End date | |
| Description | The context of this project is the uptake of cadmium (Cd) by cacao from tropical soils. Recent EU food safety regulations lowered the allowed Cd content in chocolate. This has large implications for the socio-economic sustainability of cacao production in Latin America and the Caribbean. However, one of the limitations to designing adequate management strategies to lower Cd in cacao beans is that perennial crops like cacao are heavily understudied. Hence, not much is known about the mechanisms that determine Cd uptake by cacao trees.
The objective of this thesis project is to develop a mechanistic understanding of the processes at the soil-root interface that determine Cd uptake by cacao. Plants actively modify their surroundings to influence the uptake of nutrients through the production of root exudates and mycorrhizal symbiosis. For example, the plant is expected to have developed strategies to cope with the phosphorous deficiency commonly observed in these tropical soils, which may inadvertently change Cd uptake as well. In this thesis project, you will study how root exudation and mycorrhizal colonization influence Cd uptake by cacao in response to P fertilization or the use of amendments like lime or compost. These latter two amendments are suggested to reduce Cd availability in the soil by reducing the bioavailability of Cd in the bulk soil, but less is known about the effects at the soil-root interface that ultimately determine the uptake of Cd (and essential nutrients) by the tree. You will contribute to an ongoing PhD project that is in turn part of the research-for-development project Clima-LoCa, conducted by CIAT and partners in Latin America, that aims to find practical solutions for the cadmium in cacao problem (https://ciat.cgiar.org/clima-loca/). You will be based in Cali, Colombia, at CIAT where most root exudate experiments will be carried out. There is the option to include some field work or to join sampling campaigns to visit cacao farms. |
| Used skills | • Literature review
• Writing proposal and thesis • Pot experiments and laboratory analysis • Possibly field sampling • Data processing and statistics • Presentation skills |
| Requirements | Required courses for MSc thesis Soil Biology |