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

First evidence of moisture adaptation in Zymoseptoria tritici


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

Sandrine Gélisse
UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, 78850, Thiverval-Grignon, France

Thierry Marcel
UMR BIOGER, INRA, AgroParisTech, Université Paris-Saclay, 78850, Thiverval-Grignon, France

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


Poster Presentation
Evolution and Population Biology

Atrium, UCD O'Brien centre for Science
Poster 2

View this abstract online by visting isclb2019.com/see/ABS36995

Temperature and moisture are critical micrometeorological factors affecting each epidemiological stage of foliar diseases. Several studies reported thermal adaptation of plant pathogens, including Zymoseptoria tritici, but no similar investigation has been carried out on the response and adaptation to moisture conditions. To detect if there is evidence of “moisture adaptation” in Z. tritici, we retained 48 genetically distinct isolates (already phenotyped for their thermal responses) from two populations collected in Ireland (IR) and Israel (ISR). These populations originate from contrasted climatic locations with respect to moisture conditions (annual air relative humidity - RH - of 85.1% vs 69.7%, respectively). We assayed the moisture response of these isolates on wheat seedlings during the earliest stages of infection (pycnidiospore germination, epiphytic hyphal growth and penetration). Lesion development was visually assessed under four post-inoculation RH regimes obtained by covering plants with polyethylene transparent bags for either 0, 1, 2 and 3 days post-inoculation (dpi). As expected, the longer the bagging time, i.e. the higher average RH, the more severe the symptoms were. A significant interaction between RH and population effects was established, suggesting that ISR was better adapted to lower humidity than IR. To characterize more finely this difference in phenotypic plasticity, moisture reaction norms describing the pattern of sporulating area at 14 and 17 dpi across the mean RH during the three days following inoculation were established for all isolates. Their sensitivity to RH was estimated by the slope of the linear relationship between mean RH and the percentage of sporulating area. The absence of genotypic differentiation for neutral microsatellite loci between both populations, established using 12 SSR markers, confirmed that this significant difference in RH sensitivity between IR and ISR can be interpreted as a signature of adaptation.