Supervisor
Dr Ahmed Warsame
Brief summary
Drought stress can manifest at any growth stage, and the tolerance of plants to this stress is genetically complex, involving a broad spectrum of adaptations. Genetic mapping of drought tolerance using conventional mapping populations involves screening a large number of accessions; therefore, it is essential to identify a few key drought-tolerance traits that can be measured with high accuracy and reproducibility.
Importance of Research
Owing to the changing climate, frequent droughts threaten the food security of millions of people in developing countries. This research aims to understand the morphological, physical and biochemical traits associated with drought tolerance in cowpea (Vigna unguiculata [L.] Walp.). This will facilitate the development of reliable screening techniques to map the genetic loci associated with drought tolerance in cowpea using genome-wide association studies (GWAS) and QTL mapping. This genetic information can be used in cowpea breeding programs in drought-prone areas.
Project Summary
Over 200 million people in Sub-Saharan Africa (SSA) depend on cowpea for food security and livelihoods. The crop is very resilient and is grown by smallholder farmers in the drylands of West Africa and arid regions of the Horn of Africa. These regions are characterised by erratic rainfall, and droughts are becoming more frequent due to climate change. Although improving drought tolerance in cowpea has been a major breeding objective for decades, little is known about the genetic basis of this trait. In the past, several cowpea accessions with better drought tolerance have been identified using either the survival rate at the seedling stage or yield index as an indicator of drought tolerance. However, the mechanisms of drought tolerance differ at different growth stages. For instance, at the early seedling stage, root architecture plays little role compared with the later developmental stages. Therefore, this project aims to lay the groundwork for understanding the genetic basis of drought tolerance in cowpea by identifying the key physiological and biochemical traits associated with drought tolerance at different growth stages.
What will the successful applicant do?
This project will involve a comparative characterisation of previously reported drought-tolerant and drought-susceptible accessions under controlled conditions. The student will first study the accessions under water-stressed and non-stressed treatments at different growth stages and measure the traits related to drought tolerance, including root traits, relative leaf water content, stomatal size and number, and concentration of osmolytes and reactive oxygen species (ROS). During this phase, the student will optimise the assays to ensure the accuracy and reproducibility of the data. In the second part, accessions with contrasting phenotypes will be selected to develop biparental populations to generate F2 populations, which will be phenotyped and genotyped to identify the genetic loci for drought tolerance. This will be followed by fine-mapping and validation of the candidate genes.
Training Provided
The student will gain experience with a variety of techniques, including experimental design, biochemical assays, molecular genetics, and bioinformatics. For instance, they will use different colorimetric assays to quantify drought-stress related compounds, employ microscopy and image analysis to study stomatal traits, extract and sequence genomic DNA, and use different bioinformatics pipelines to uncover the genetic loci underlying drought tolerance. The student will be supported and any relevant training will be provided.
References
1. Boukar, O., et al., Cowpea (Vigna unguiculata): Genetics, genomics and breeding. Plant Breeding, 2019. 138(4): p. 415-424. doi: /10.1111/pbr.12589
2. Shen, J., et al., Physiology and transcriptomics highlight the underlying mechanism of sunflower responses to drought stress and rehydration. iScience, 2023. 26(11): p. 108112. doi: 10.1016/j.isci.2023.108112
3. Wang, X., et al., Genetic variation in ZmVPP1 contributes to drought tolerance in maize seedlings. Nature Genetics, 2016. 48(10): p. 1233-1241. doi: 10.1038/ng.3636
4. Mei, F., et al.,https://doi.org/10.1038/ng.3636): p. 4472-4494. doi: 10.1038/ng.3636
5. Tian, G., et al., Allelic variation of TaWD40-4B.1 contributes to drought tolerance by modulating catalase activity in wheat. Nature Communications, 2023. 14(1). doi: 10.1038/s41467-023-36901-6