An investigation into the genetic forces shaping the LOP Locus of Pilosella piloselloides var praealta : A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Applied Science at Lincoln University

Abstract

Gametophytic Apomixis, a form of asexual reproduction that bypasses meiosis and fertilisation, enables plants to produce seeds that are genetically identical to the female parent. It is a potentially revolutionary technological advance for global food security, enabling accelerated plant breeding and seed production. There are three critical processes employed by gametophytic apomicts for clonal seed production. These are ‘Apomeiosis’ (the avoidance of meiosis), ‘Parthenogenesis’ (embryo formation without fertilisation) and Autonomous Endospermy (endosperm formation without fertilisation). In the model apomict, Pilosella piloselloides var. praealta, the asexual dominant allele at the LOP locus (LOP), has been identified as a critical element involved in the avoidance of fertilisation. Recently, LOP has been mapped to a 654kb region of the genome (Bicknell et al. 2023). This thesis builds on this discovery and the finding that the dominant PARTHENOGENESIS (PAR) gene, shown to drive spontaneous embryo formation in Taraxacum, is positioned at one end of the defined 645kb LOP allele (Underwood et al. 2022). This positioning poses a compelling question about the forces driving the structure of this allele: Is the structure of LOP due to genetic co-inheritance, requiring the two extreme ends of the allele to be inherited together for its function, or does the suppression of recombination at the locus ensure that the entire genetic region is inherited as a single unit? Ultimately, this thesis tests the hypothesis that: The co-inheritance of multiple genes within the 654kb LOP region is necessary to elicit LOP function in the model apomictic in P. piloselloides var. praealta R35. The null hypothesis is that only PAR is required for LOP function.