Nevescanin Moreno, Antonia Lucia Guadalupe
(2024)
Characterization of wheat root traits for adaptability to abiotic stress.
PhD thesis, University of Nottingham.
Abstract
Agricultural production seems to have a hostile future, current agrosystems are facing a tough reality coping with complex challenges like a growing population and climate change; this means breeders must not just meet the production demand, but also improve the capacity of the crops to fit in new adverse climate conditions. Wheat is not the exception of these problems and it has a big area of opportunity related to crop improvement. Plant phenotyping is a powerful tool that helps to identify the traits which shall be necessary as inputs to design well adapted crops, but it´s well known that most of the attention is on the aboveground part of the plant. Despite playing a crucial role in acquiring resources, roots are often neglected mainly because of the challenges associated with measuring belowground structures. Thus, the aim of this PhD project is to identify wheat root traits for improved adaptation to diverse environmental stressors, by characterizing root traits for drought and heat adaptation and utilizing hormone related sensitivity as an innovative approach to predict and enhance root growth under soil compaction conditions.
Field trials were conducted to assess the effect of drought and heat in spring wheat roots. Morphological (diameter) and architectural (biomass production/distribution, number and angle) root traits were measured and then correlated with agronomic traits. Results exhibited that drought stress had a more pronounced effect on root biomass compared to heat stress. Under drought, genotypes allocated more resources to canopy biomass, while under heat, investment increased in belowground biomass. Root diameter was thinner by drought stress only, root number reduced by both drought and heat stress, and crown angle remained unaffected by stress conditions. Correlations between agronomic root traits suggest that the root system ideotype for high yield and canopy biomass under drought stress conditions is a wheat plant with a steep root system, low shallow root biomass production and thin roots. For heat stress conditions, the ideotype proposed is a wheat plant with deeper accumulation of root biomass, steeper root system and lower nodal root production.
A high throughput screening for ethylene sensitivity in wheat genotypes was conducted to assess their root growth inhibition. A subset of genotypes was tested in compacted soil using X-Ray Computed Tomography and results exhibited that higher root ethylene sensitivity correlates with reduced root growth under soil compaction. To explore the influence of soil properties on root ethylene sensitivity, soil texture geographical information of where landraces have been historically grown was compared to the root growth inhibition by ethylene. The results demonstrated a correlation between the diversity in wheat root ethylene response and contrasting soil textures. Three promising candidate genes (Transmembrane protein 184C, Cyclin and Catalase) were identified on Chromosome 7A from the GWAS analysis on the Watkins population. Bioassays of TILLING mutants on roots identified the Catalase gene (TraesCS7A02G549800) as the top candidate for regulating ethylene sensitivity.
This thesis investigated root traits in wheat that improve adaptation to drought, heat, and soil compaction. Field trials identified root traits associated with stress tolerance, and high-throughput screening revealed a link between ethylene sensitivity and root growth under soil compaction. This research suggests specific genes potentially regulating root's response to soil compaction stress.
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