Nematodes belong to one of the most diverse phyla on the planet. Most nematodes are free living and feed on bacteria, fungi, and protozoa. Plant-parasitic lifestyles are relatively rare in terms of numbers, however, through their parasitism these nematodes have a substantial impact on agriculture. They are estimated to account for over 10% of the annual life-sustaining crop losses, costing the industry roughly 100 billion U.S. dollars per year. There are two major groups of plant-parasitic nematodes: endoparasites and ectoparasites. The endo-parasites are the most economically important, and consequently the most widely studied. Endo parasitic nematodes, e.g., cyst nematodes, spend most or in some cases their entire life within the host, and feed exclusively on living host tissue.

Cyst nematodes alter the expression of a multitude of host genes, to coordinate the formation of a syncytial feeding-site. Loss in the ability to anipulate host genes required for the formation of this syncytium has a negative impact on parasitism: resulting in reduced nematode size and/or a reduction in the infection frequency. Given the intuitive pathways to impact from this fundamental understanding, there is considerable interest in the field to identify these, so called, susceptibility genes and the mechanisms by which they are manipulated.

This thesis describes and discusses efforts to expand the genetic toolkit for the plant- and nematode-side of the interaction to accelerate the study of the pathology as a whole. The thesis is principally focused on the model cyst nematode Heterodera schachtii due to its ability to parasitise the model plant Arabidopsis thaliana.

Knowledge on the nematode-side of the host-parasite interaction remains limited, partially due to the lack of functional genetic tools. Prior to this work, there was no method available to interrogate nematode gene “gain-of-function”, and only one method (RNA-interference) available to interrogate nematode gene "loss-of-function". The first experimental chapter details a body of work aimed to address this constraint. It describes various attempts to deliver and express foreign genetic material in plant-parasitic nematodes using liposome-based transfection. Ultimately, the first gain-of-function experiments are demonstrated for any plant parasitic nematode. Exogenous mRNA encoding eGFP and Luciferase are delivered to, and translated, in Nematoda.

On the plant-side of the interaction, functional genetic tools are already well established. The challenge is phenotyping of parasitism. Historically, infection is quantified by eye under the microscope. The main limitations of this approach are: 1) the relatively small number of technically tractable phenotypes (i.e., number of nematodes); and 2) the laborious nature of quantification. The second chapter describes efforts to lift both constraints using custom 3D printed hardware and software to essentially digitise the assay. This new approach facilitates the measurement of infection, provides new phenotypes for analysis, and ultimately sets the stage for large-scale forward genetic screens.

Finally, the ability of this new screening method to facilitate the identification of new S genes was demonstrated. An experiment was conducted to measure the transcriptional response of A. thaliana shoot infection by H. schachtii. These data were cross-referenced to a published dataset of the transcriptional response of A. thaliana root infection to define a tissue independent response to nematode parasitism. To identify new putative S genes, a screen of mutants of differentially regulated genes was conducted using the new phenotyping capability.

Taken together, this work expands the tools available for the study of cyst nematodes demonstrating: 1) expression of exogenous genes in Nematoda; 2) digitisation of nematode phenotyping; and 3) identification of putative S genes by combining tissue-specific infection datasets.