Assessing the factors affecting dispersal and colonisation of fungal plant pathogens across multiple ecological scales

Abstract

The spread of agricultural plant pathogens is a global problem; 20-40% of crop yield globally are lost to animals, weeds and pathogens, with ~12% of total crop production lost to plant diseases. To date, the most widely used form of control is chemical biocides, however with concern regarding sustainability and toxicity, there is a pressing need to shift to more holistic approaches. To address this need, this thesis begins the essential task of understanding the influence of biotic and abiotic factors on the movement of fungal pathogens and pathogen suppression. Specifically, this thesis investigated the role of soil microbial communities in suppressing the spread of plant pathogens using Fusarium as a model plant pathogen. Using a combination of laboratory experiments, a greenhouse survey (case study) and landscape surveys, this thesis spans multiple scales to provide a comprehensive assessment of the fungal pathogen Fusarium; its dispersal, spread and methods of mitigation. This thesis provided the first empirical data on fungal spillover and highlights the importance of landscape habitats in plant-pathogen dispersal; with woodland soils presenting a hard-edge boundary for fungal plant-pathogen presence/abundance. Moreover, this thesis experimentally demonstrates the importance of both the soil type (parental material) and resident microbial community on fungal suppression; specifically, although woodland soils allow for faster movement and greater dispersal (distance) of Fusarium, the resident microbial community acts as a barrier. This surrounding community also plays a key role in Fusarium dynamics alongside mitigation methods; sterilization methods used to kill pathogens also kill the resident community and ultimately, this allows for the re-emergence of Fusarium. With these results, this thesis opens avenues of study that focus on utilising woodland soil, and its corresponding community, as a mitigation tool in both mid (enclosed/protected e.g. greenhouses) and large scales (agricultural landscape). Firstly, results suggest that woodland soils can be utilized alongside sterilised methods by seeding sterile soil with woodland communities to provide a biotic competitive barrier, and subsequently hindering pathogen growth. Secondly, results suggest the use of woodlands border around patches of agricultural fields could act as a method of isolating plant pathogens within patches and subsequently reducing disease spread. Harnessing woodland soils’ natural inhibitory properties has the potential to provide sustainable, holistic and viable alternatives to current methods.