A theoretical framework for the spatial spread of soil-borne fungal plant pathogens

• Main Author: Hollingsworth, Teresa Déirdre
• Published: University of Cambridge 2004
• Subjects: 632
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604173

The spread of mycelia through soil is the main process by which many economically important plant pathogens are transmitted between plants. Using mathematical modelling, this thesis provides a framework for investigating the interaction between soil structure and fungal growth, with a view to controlling this spread. Fungal dynamics are modelled at the scale of groups of hyphae by a stochastic cellular automaton (CA), with the cells of the CA corresponding to the network of pore species in the soil. The fungal model captures the characteristics of mycelial growth at this scale, whilst maintaining a level of mathematical tractability. The growth of mycelial fungi within and between patches is modelled by the rates of growth and quiescence, or transition to inactivity, together with structural parameters. The fungal model is analysed to identify key characteristics of the pore network which affect the morphology of the fungal colony. The soil-pore network is modelled as part of the entire soil structure. The pore space is abstracted to a network of connected patches of different sizes. The size and connections between these patches are converted into carrying capacities for hyphal colonisation and the level of connection between cells for subsequent implementation of the fungal model. The models are used to give insight on experimental data for soils of different bulk densities. The application of the soil and fungal models to this data allows the three-dimensional structure of the soils to be studied, and changes in the three-dimensional connectivity which contribute to changing hyphal density are identified. The results show that at low bulk densities there are few large, pore spaces with connections to distant pore spaces. This structure results in large sparse colonies. At high bulk densities, the pore space is made up of many smaller pore spaces which are connected to a few close pores. This structure results in small, dense colonies.