Investigating Biofumigation for the Control of Plant-Parasitic Nematodes

The white potato cyst nematode, Globodera pallida, is an important pest of potato in all potato-growing regions of the world and is of particular importance to UK agriculture, found in 48-64 % of UK potato fields and incurring costs related to management and yield losses. Biofumigation is a pest management practice that seeks to exploit the production of bioactive compounds, isothiocyanates, from disrupted brassica tissues incorporated into soil. Aspects of biofumigation as they relate to control of G. pallida were investigated. The xenobiotic metabolism of G. pallida juveniles in response to contact with isothiocyanates was investigated through RNAseq analysis of nematodes exposed to Dazomet, an isothiocyanate generator. The roles of genes implicated in this response were investigated and their up-regulation confirmed, identifying several genes directly implicated in detoxification of xenobiotic compounds, presenting targets for development of future controls. A screening system for evaluation of novel biofumigant crops was developed, utilising Caenorhabditis elegans reporter lines that indicated the presence of isothiocyanates through induced expression of green fluorescent protein (GFP). Attempts to generate novel C. elegans reporters for G. pallida genes were unsuccessful, but progress was made towards generation of transgenic root-knot nematodes, a step towards a plant-parasitic nematode model system. The volatile emissions given off by brassicas as they grow were measured and a number of bioactive compounds were identified. New estimates of the contributions of brassicas to atmospheric methyl bromide concentrations were generated. A system was developed to test the toxicity of volatile compounds as given off by the above- and belowground biomass of brassicas, and toxicity was observed in C. elegans adults and G. pallida juveniles and encysted eggs. The approaches taken to investigate biofumigation are novel and support expansion of the scope of future biofumigation research in line with the findings presented.