TY - JOUR T1 - Natural selection drives population divergence for local adaptation in a wheat pathogen JF - bioRxiv DO - 10.1101/805127 SP - 805127 AU - Danilo Pereira AU - Daniel Croll AU - Patrick C. Brunner AU - Bruce A. McDonald Y1 - 2020/01/01 UR - http://biorxiv.org/content/early/2020/03/27/805127.abstract N2 - Evolution favors the emergence of locally-adapted optimum phenotypes that are likely to differ across a wide array of environmental conditions. The emergence of favorable adaptive characteristics is accelerated in agricultural pathogens due to the unique properties of agro-ecosystems. We performed a QST - FST comparison using 164 strains of Parastagonospora nodorum sampled from eight global field populations to disentangle the predominant evolutionary forces driving population divergence in a wheat pathogen. We used digital image analysis to obtain quantitative measurements of growth rate and melanization at different temperatures and under different fungicide concentrations in a common garden experiment. FST measures were based on complete genome sequences obtained for all 164 isolates. Our analyses indicated that all measured traits were under selection. Growth rates at 18°C and 24°C were under stabilizing selection (QST < FST), while diversifying selection (QST > FST) was the predominant evolutionary force affecting growth under fungicide and high temperature stress. Stabilizing selection (QST < FST) was the predominant force affecting melanization across the different environments. Melanin production increased at 30°C but was negatively correlated with higher growth rates, consistent with a trade-off under heat stress. Our results demonstrate that global populations of P. nodorum possess significant evolutionary potential to adapt to changing local conditions, including warmer temperatures and applications of fungicides. ER -