Measurement of infection efficiency of a major wheat pathogen using time‐resolved imaging of disease progress

Abstract

Infection efficiency is a key epidemiological parameter that determines the proportion of pathogen spores able to infect and cause lesions once they have landed on a susceptible plant tissue. In this study, an improved method to measure infection efficiency of Zymoseptoria tritici using a replicated greenhouse experiment is presented. Zymoseptoria tritici is a fungal pathogen that infects wheat leaves and causes septoria tritici blotch (STB), a major disease of wheat worldwide. A novel experimental setup was devised, where living wheat leaves were attached to metal plates, allowing for time‐resolved imaging of disease progress in planta. Because lesions were continuously appearing, expanding and merging during the period of up to 3 weeks, daily measurements were necessary for accurate counting of lesions. Reference membranes were also used to characterize the density and spatial distribution of spores inoculated onto leaf surfaces. In this way, the relationship between the number of lesions and the number of viable spores deposited on the leaves was captured and an infection efficiency of about 4% was estimated from the slope of this relationship. This study provides a proof of principle for accurate and reliable measurement of infection efficiency of Z. tritici. The method opens opportunities for determining the genetic basis of the component of quantitative resistance that suppresses infection efficiency. This knowledge would improve breeding for quantitative resistance against STB, a control measure considered more durable than deployment of major resistance genes.

A new mechanistic model of weather-dependent Septoria tritici blotch disease risk

“…[24,25]) specifically consider wheat growth stage as a proxy for leaf availability for infection and lesion development, while model A assumes that if a spore can grow, it can cause a lesion. However, saturation of lesion formation following leaf inoculation with increasing numbers of spores has been demonstrated [39,43]. Depending on disease progression and the timing of disease observation, this may cause model A to over- or underestimate disease risk.…”

Spatially explicit ecological modeling improves empirical characterization of dispersal

“…Dierence between these may arise from possibly 734 density-dependent post-dispersal mortality (Nathan et al, 2012;Klein et al, 2013). At high spore densities, that can be found close to the source, leaves can become saturated 736 with the infection leading to a decreased infection eciency of spores (Karisto et al, 2019). In the tail of the distribution the density is however so low, that saturation may for a dierent approach.…”

“…x 0 from t 0 to t 1 was not only due to secondary infections but also from extremely long latent periods (Karisto et al, 2019). Additionally, possible saturation was strongest at 762…”

Dissecting the Biology of the Fungal Wheat Pathogen Zymoseptoria tritici: A Laboratory Workflow

“…Infection of other highly susceptible wheat cultivars can be used to compare the virulence of different Z. tritici genotypes. The cultivars Obelisk, Riband, and Drifter are highly susceptible to IPO323 and to a large number of other isolates and are therefore commonly used in pathogenicity assays to quantify and compare virulence (Chartrain, Brading, & Brown, 2005;Habig et al, 2017;Haueisen et al, 2019;Karisto, Dora, & Mikaberidze, 2019;Stewart & McDonald, 2014;Zhong et al, 2017).…”