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Genetic determinants of stomatal density for enhanced water-use efficiency in barley (Hordeum vulgare)

Robertson, Brittany Clare (2021) Genetic determinants of stomatal density for enhanced water-use efficiency in barley (Hordeum vulgare). Honours thesis, Murdoch University.

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Low stomatal density correlates with robustness to water deprivation and thus holds potential for the improvement of water-use efficiency (WUE) of commercially relevant crops grown in drought-prone environments. Ranking fourth in terms of global agricultural production, barley (Hordeum vulgare L.) is especially amenable to reductions in stomatal density without the caveat of yield impacts. In this study, a collection of 313 diverse barley accessions with global geographic origins was screened revealing varieties with low stomatal densities for use in future breeding programs. Through genome-wide association analysis (GWAS) of the globally derived barley population, 17 quantitative trait loci (QTLs) were identified for the trait of stomatal density for use in molecular marker-assisted breeding strategies. The identification of numerous QTLs confirmed that stomatal density in barley is controlled by multiple genetic loci. QTLs revealed following GWAS analysis were aligned to the reference genome and led to the identification of seven candidate genes for stomatal density in barley. A novel candidate gene encoding a putative subtilisin-like protease was revealed following GWAS analysis, located 63Kb (Kilo base pairs) upstream of a QTL identified on chromosome 4. Functional prediction of the candidate gene was ascertained based on sequence homology with the gene ortholog encoding the subtilisin-like protease SDD1 (STOMATAL DENSITY AND DISTRIBUTION 1), a known negative regulator of stomatal density in Arabidopsis thaliana. A gene-specific molecular marker was designed for the candidate gene encoding a subtilisin- like protease to select for offspring possessing the candidate gene sequence from low stomatal density barley varieties in subsequent breed improvement. The discovery of the novel candidate gene encoding a subtilisin-like protease indicates that conservation of the stomatal development network extends into the barley lineage. The candidate gene encoding a subtilisin-like protease holds potential for the future improvement of WUE in barley.

Item Type: Thesis (Honours)
Murdoch Affiliation(s): Medical, Molecular and Forensic Sciences
Supervisor(s): Li, Chengdao, Zhang, Xiao-Qi, He, Tianhua and Angessa, Tefera
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