SEIR model functioning
The main output computed by the epidemiological model is the disease severity, intended as the proportion of host tissue affected compared to the total host tissue. The epidemiological model can be parameterized to reproduce the progress of the epidemics caused by different fungal pathogens on several crops, by changing model parameters. A graphical representation of the simulation of the epidemic development and of the processes simulated by the DiseaseProgress component is shown in the figure below.
Graphical representation of the processes simulated by the DiseaseProgress component
The model considers the following components of the infection process: infection, incubation, latency, infectiousness, sporulation, spore dispersal. These processes, which are driven by weather conditions and interactions with the host plant, are simulated as a function of meteorological variables and biological significant parameters. The affected host tissue is classified in four different state variables, on the basis of specific stages of epidemic:
Once the infection process has successfully taken place, the host tissue interested by this new infection is in the state of HostTissueLatent, that means that the infection is in progress, but no symptoms are visible yet. Once the incubation period has accomplished, the infected area of host tissue passes to the state of HostTissueVisible, with disease lesions visible, but not yet producing spores. At the completion of the latent period, the infected portion of host tissue evolves to the HostTissueInfectious state, since spores, able to cause new infections, start to be produced on the disease lesions. The sporulation proceeds until the infectiousness period is over and the lesions become old and sterile. The infected portion of host tissue passes, then, to the HostTissueSenescent state and does not further contribute to the epidemic.
The spores produced on the disease lesions can be dispersed by rain or wind and, once deposited on the surface of host tissue susceptible, they can cause new infections, if the environmental conditions are conducive.
Sample output of the DiseaseProgress component, showing the percentage of host tissue
affected by the different phases of the epidemic
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