Verbetering van de watergebruiksefficiëntie in cassaveteeltsystemen met behulp van stabiele isotopentechnieken
Year: 2025
Type: dissertation
Abstract: Cassava (Manihot esculenta Crantz) is a tuberous root crop grown in the tropics, serving as both an important staple food and a valuable cash crop. Although cassava is considered drought-tolerant, the increasing frequency and intensity of droughts due to climate change represent a growing threat to its production. To address these challenges, it is crucial to develop strategies that enhance cassava resilience and productivity under adverse conditions. A promising strategy to improve crop growth under limited rainfall is to maximize root production per unit of water used, or water use efficiency (WUE), by using improved varieties or adapting agronomic practices. While WUE assessments of a field trial can be time consuming, leaf based approaches, such as intrinsic water use efficiency, only provide snapshots in time . We therefore investigated the potential of stable isotopes (δ13C and Δ18O), indicators of intrinsic water use efficiency integrated over longer time scales, to asses water use efficiency in cassava plants as well as their utility to understand carbon dynamics. In a greenhouse experiment, we labelled cassava plants with 13C-CO2 and found increased respiration due to drought and modified carbon partitioning due to drought and potassium application. In another experiment, we showed that potassium and drought can affect δ13C and water use efficiency. Older leaves and recent assimilates showed the strongest changes in δ13C. However, plants with higher intrinsic WUE (δ13C) showed lower whole plant WUE. In a field trial with 14 cassava genotypes, we found strong genotypic effects on δ13C and good correlations with yield in a dry environment, depending on the sampled carbohydrate pool and leaf position, highlighting its potential to select adapted varieties. While fertilizer application increased intrinsic WUE (δ13C) in another multi-location field trial, no effects of weeding were found on δ13C, possibly due to morphological changes, counteracting physiological changes. No changes in Δ18O were detected. Here, δ13C in the upper leaves was more strongly related to environmental fluctuations, whereas δ13C in the lower leaves was more related to leaf nitrogen content. We demonstrated the potential of stable isotope composition to detect changes in intrinsic WUE from genotype selection and agronomic practices. However, increased intrinsic WUE may be linked to decreased whole plant WUE and reduced yields. Interpreting stable isotope composition therefore requires an understanding of the cropping system and its environment. This work highlights the importance of sampling the right carbohydrate pool and leaf position and can form the basis for further ecophysiological research in cassava.
Source: Lirias
Author: Van Laere, Jonas
Institution: KU Leuven
Language: English
Subfield: Global and Planetary Change
Field: Environmental Science
Domain: Physical Sciences
SDGs: Zero hunger, Climate action
Open Access status: green
OpenAlex ID: W7113259003
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