With the requirement to breed more productive crop plants in order to feed a growing global population, compounded by increasingly widespread resistance to pesticides exhibited by pathogens, plant immunity is becoming an increasingly important area of research. Of the genes that contribute to disease resistance, the wall-associated receptor-like kinases (WAKs) are increasingly shown to play a major role, in addition to their contribution to plant growth and development or tolerance to abiotic stresses. Being transmembrane proteins, WAKs form a central pillar of a plant cell’s ability to monitor and interact with the extracellular environment. Found in both dicots and monocots, WAKs have been implicated in defence against pathogens with diverse lifestyles and contribute to plant immunity in a variety of ways. Whilst some act as cell surface-localized immune receptors recognizing either pathogen- or plant-derived invasion molecules (e.g. effectors or damage-associated molecular patterns, respectively), others promote innate immunity through cell wall modification and strengthening, thus limiting pathogen intrusion. The ability of some WAKs to provide both durable resistance against pathogens and other agronomic benefits makes this gene family important targets in the development of future crop ideotypes and important to a greater understanding of the complexity and robustness of plant immunity.

Septoria tritici blotch (STB), caused by the fungus Zymoseptoria tritici, is one of the most economically important diseases of wheat. Recently, both factors of a gene-for-gene interaction between Z. tritici and wheat, the wheat receptor-like kinase Stb6 and the Z. tritici secreted effector protein AvrStb6, have been identified. Previous analyses revealed a high diversity of AvrStb6 haplotypes present in earlier Z. tritici isolate collections, with up to c.18% of analysed isolates possessing the avirulence isoform of AvrStb6 identical to that originally identified in the reference isolate IPO323. With Stb6 present in many commercial wheat cultivars globally, we aimed to assess potential changes in AvrStb6 genetic diversity and the incidence of haplotypes allowing evasion of Stb6-mediated resistance in more recent Z. tritici populations. Here we show, using targeted resequencing of AvrStb6, that this gene is universally present in field isolates sampled from major wheat-growing regions of the world in 2013-2017. However, in contrast to the data from previous AvrStb6 population studies, we report a complete absence of the originally described avirulence isoform of AvrStb6 amongst modern Z. tritici isolates. Moreover, a remarkably small number of haplotypes, each encoding AvrStb6 protein isoforms conditioning virulence on Stb6-containing wheat, were found to predominate among modern Z. tritici isolates. A single virulence isoform of AvrStb6 was found to be particularly abundant throughout the global population. These findings indicate that, despite the ability of Z. tritici to sexually reproduce on resistant hosts, AvrStb6 avirulence haplotypes tend to be eliminated in subsequent populations.

The aim of this thesis is to argue for a new metric for determining the moral status of another being. Determining this status is of foundational importance in a number of legal, political, and ethical concerns, including but not limited to animal rights, the treatment of criminals, and the treatment of the psychologically afflicted. This metric will be based upon one’s capacity to morally consider others. In other words, in order to have full moral status, one must be able to have moral concern for others and act upon this concern to even a minimal degree. In doing so, one will be considered to belong to a “moral community”, which affords the member a certain set of rights, privileges, and duties towards other community members. Arguing for the existence of such a community achieves the pragmatic aspect of this thesis. I argue that morality is geared towards group-survival strategies which have been evolutionarily selected for, and thus by organizing societal structures towards the tools which nature has armed us with, we may maximize the powers and capacities of the community members. In order to achieve these aims, I defend a concept of morality as based in emotion, requiring certain neurological structures, which gives the first set of criteria for identifying potential members of the moral community. I then discuss the issue of identifying the capacity for morality in non-human minds, arguing that we may infer moral capacities from behaviourism. In summary, the findings of this paper are that first, morality is essentially emotional in nature and is a product of the nature of our neurological system, although rational processes and enculturation shape particular moral sensitivities and priorities. Second, one can infer the existence of moral capacities in animals from their behaviour, and, at risk of engaging in anthropomorphism, to deny these capacities completely entails solipsism. Thirdly, and most importantly, those who are capable of morally considering others ought to be afforded full moral status themselves and be brought into a “moral community” wherein special rights, freedoms, and privileges allow the members to most efficiently contribute to the community, maximizing the powers and benefits of the community. Stellenbosch University https://scholar.sun.ac.za