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Modelling the key drivers of an aerial Phytophthora foliar disease epidemic, from the needles to the whole plant

Abstract : Understanding the epidemiology of infectious diseases in a host population is a major challenge in forestry. Radiata pine plantations in New Zealand are impacted by a foliar disease, red needle cast (RNC), caused by Phytophthora pluvialis. This pathogen is dispersed by water splash with polycyclic infection affecting the lower canopy of the tree. In this study, we extended an SI (Susceptible-Infectious) model presented for RNC to analyse the key epidemiological drivers. We conducted a detached-needle assay and an in vivo inoculation experiment to empirically fit the model. With the detached-needle assay data we compared resistant and susceptible genotypes, and with the in vivo inoculation data we informed sustained infection of the whole plant. We also compared isolations and real-time quantitative PCR (qPCR) to assess P. pluvialis infection. While susceptible and resistant genotypes presented similar primary infection rates and incubation times, the pathogen death rate was 2.5 times higher for resistant genotypes. External proliferation of mycelium and sporangia was only observed on 28% of the resistant ramets compared to 90% of the susceptible ones. Detection methods were the single most important factor influencing model parameter estimates for the whole-plant infection, giving qualitatively different epidemic outputs. In the early stages of infection, qPCR proved more efficient than isolations but the reverse was true at later points in time. Our results have important implications to the management of RNC, by highlighting the main differences between susceptible and resistant genotypes, and comparing the most common assessment methods to detect RNC epidemics.
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https://hal.univ-lorraine.fr/hal-03220961
Contributor : Mireia Gomez Gallego <>
Submitted on : Friday, May 7, 2021 - 3:52:49 PM
Last modification on : Saturday, May 8, 2021 - 3:09:01 AM

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  • HAL Id : hal-03220961, version 1

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Mireia Gómez-Gallego, Ralf Gommers, Martin Karl-Friedrich Bader, Nari Michelle Williams. Modelling the key drivers of an aerial Phytophthora foliar disease epidemic, from the needles to the whole plant. 9th Meeting of the IUFRO Working Party 7.02.09: Phytophthora in Forests and Natural Ecosystems, Oct 2019, La Maddalena, Italy. ⟨hal-03220961⟩

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