International Symposium on Cereal Leaf Blights 2019 | University College Dublin, Ireland | 22-24 May 2019

Hectic Life on Wheat Leaves: Dynamics of Phenotypic Selection within Zymoseptoria tritici Populations Facing Microclimatic Heterogeneities

Anne-Lise Boixel*
UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, 78850, Thiverval-Grignon, France

Michaël Chelle
UMR ECOSYS, INRA, AgroParisTech, Université Paris-Saclay, 78850, Thiverval-Grignon, France

Frédéric Suffert
UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, 78850, Thiverval-Grignon, France

Oral Presentation
Evolution and Population Biology

Moore Auditorium, UCD O'Brien centre for Science
22 May 2019, 11:20

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Wheat foliar pathogens inhabit crop canopies that are subjected to substantial spatio-temporal variations in temperature. Given the pronounced diversity in thermal individual responses within a local Zymoseptoria tritici population, these environmental heterogeneities may lead to phenotypic selection in the field. Signatures of response to thermal selection over the course of annual Septoria tritici blotch (STB) epidemics have been previously identified. However, the consequences on population dynamics of the interplay between interindividual phenotypic variation and thermal canopy heterogeneity have not yet been investigated. We address this issue using a three-step approach. First, we quantified the extent of environmental (measurement of temperature distribution within wheat canopies) and phenotypic (standardised thermal phenotyping of Z. tritici) variations encountered by or in natural pathogen populations. Second, we dissected the processes underlying spatio-temporal changes in the phenotypic composition of populations facing different types and extent of microclimatic heterogeneities by performing in planta polycyclic selection experiments (growth chamber and field experiments). Third, we explored in silico the way in which phenotypic diversity affect population adaptive dynamics (quantitative assessments of population vulnerability and resilience to thermal changes). Our results show how environmental signals, interindividual phenotypic variations and ecological processes have affected Z. tritici population dynamics in our experiments. In particular, three major findings emerged from this investigation: (i) the occurrence and the epidemiological consequences of short-term selection driven by seasonal temperature variations over an annual epidemic; (ii) the critical importance of spatio-temporal thermal heterogeneity in wheat canopies in the maintenance of phenotypic diversity within Z. tritici populations through the presence of thermal refugia; (iii) the quantitative impacts of oversimplifications currently adopted in disease prediction models. By shedding new light on population adaptive potential to environmental variations, these insights would help to improve predictions of the eco-evolutionary responses of populations to changing climate.