Genome dosage, genetic hybridity and crop improvement

Abstract

Plant breeding is focussed on introducing novel traits in plants, as well as enhancing or repressing traits already present. A noble objective in agriculture is to produce more food per unit area with overall fewer resources. Plant breeders have a central role to play in achieving this objective. My PhD research investigates the genetic and physiological consequences of two different plant breeding phenomena: heterosis and polyploidy. Heterosis occurs when different parents of the same species are interbred and the offspring display enhanced characteristics, such as higher yield. Polyploidy is when an organism possesses more than two sets of chromosomes. Humans, for example, are diploid organisms with just two sets of chromosomes (we inherit one set from our mother and one from our father), but polyploidy is common in both wild and cultivated plants. In chapter one of this thesis I discuss the most relevant and most recent literature. Next, I present five research chapters composed of varied research methodologies, from classical botany to the latest gene sequencing technologies. In chapter two I investigate if the heterosis phenomenon in sugar beet can be improved by increasing the number of paternally inherited chromosome sets. In chapter three I utilise tetraploid plants to investigate for the presence of progressive heterosis in Arabidopsis thaliana. In chapter four I investigate if a novel method of whole-genome elimination in plant breeding is influenced by nuclear and cytoplasm effects. In chapter five I investigate whether the induction of polyploidy, including whether a chromosome set is inherited maternally or paternally, can enhance salt stress tolerance in Arabidopsis thaliana. In chapter six I model the impact of climate change on land suitability of related lower and higher ploidy grasses.