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The domestication of plants and animals has been a powerful force in the development of human societies over the past millennia. Domestication of plants is underscored by the selection of agriculturally favourable traits, such as flowering time and disease resistance, which are often inherited in a quantitative manner. Advances in techniques relating to the study of quantitative traits over the past decades enable the dissection of the genetic architecture and molecular basis of these traits. In this thesis, I discuss the natural diversity governing flowering time and intermediate nonhost resistance in the non-domesticated grass Brachypodium distachyon. Three major loci were found to govern flowering time, two of which colocalise with the B. distachyon homologs of major flowering pathway genes identified in crop species. However, the identification of additional loci suggests that greater complexity underlies flowering time in this non-domesticated system. In contrast, a natural stack of three resistance genes protects B. distachyon against colonisation by Puccinia striiformis and highlights a relatively simple genetic architecture for intermediate nonhost resistance. One broad spectrum major effect locus was narrowed down to genes that are commonly associated with isolate-specific host resistance While it has been proposed that nonhost and host resistance are inherently different, the genetic architecture and molecular basis of resistance in this intermediate nonhost system is reminiscent of a host system, which suggests that the genetic architectures of host and nonhost systems are structurally coupled and share conserved components. Studying the genetic basis of these quantitative traits in B. distachyon elucidates the way humans have utilised the natural variation present in grasses to create modern temperate cereals. Additionally, exploring the interaction between B. distachyon and P. striiformis has provided an ideal system to investigate the transfer of resistance genes from wild relatives to agronomically important crops. |
