ABSTRACTS SUBMISSION 66_Amir Hossein FARTASH ‐ inp ‐ France amirhossein.fartash@toulouse‐inp.fr Climate change and global trade will challenge genetic resistance to Verticillium wilt in the legume plant Medicago truncatula Fartash A. A, Mazurier M. A, Ghalandar M.B Ebrahimi A. C, Ben C. A, Gentzbittel L.A, Rickauer M.A ALaboratoire Ecologie Fonctionnelle et Environnement, Universit´e de Toulouse, CNRS, Toulouse, France, B Agricultural Research Centre of Markazi Province, PO Box 889, Arak, Iran, C Faculty of Agriculture and Natural Resources, Science and Research Branch, Islamic Azad University, Ashrafi Esfehani Highway, BP 1477893855 Tehran, Iran. Verticillium wilt is caused by species of the soilborne fungus Verticillium and affects more than 200 plant species. Verticillium wilt of alfalfa (Medicago sativa) is a major problem for this crop. Its close relative Medicago truncatula, a wild species growing all around the Mediterranean, is a model plant in legume biology and is used widely to study genetic control of disease resistance. We previously described the genetic architecture for quantitative resistance to the French V. alfalfae strain V31.2 (1, 2) and described correlation between resistance and population structure (3). Our present study aims to assess effects of climate change and globalization on genetic resistance to V. alfalfae. Hence we isolated V. alfalfae strains from alfalfa in Iran and conducted inoculation experiments at 25°C compared to the standard temperature of 21°C. Fungal isolates were identified by PCR with V. alfalfae ‐specific primers and characterized by their reproductive and vegetative characteristics at 3 temperature. One Iranian isolate was selected for further studies. The plant’s response to this strain was assessed by scoring disease symptoms during 4 weeks after root inoculation in 242 M. truncatula accessions. Area Under disease progress curve (AUDPC) and Maximum symptom scoring (MSS) were computed as phenotypic traits. Genome‐wide association analysis was performed with 5,671,743 SNPs and revealed 30 loci associated to resistance traits MSS and AUDPC. Except one, all loci are different from those identified previously with V31.2 at 20°C. This clearly shows the strong effect of environment and fungal strain and not only challenges crop breeders to prepare for future conditions influenced by climate change and the introduction of pathogens by global trade, but also calls for surveillance in natural ecosystems. 1. Ben et al., 2012, J. Exp. Bot, 64(1):317‐32. 2. Mazurier 2018, PhD thesis Université de Toulouse, INP‐ENSAT 3. Gentzbittel et al., 2019, Genome Biol., 20, 106. 1. What is your pathogen? Multiple options possible (e.g. if working on coinfections) Fungi : Verticillium alfalfae 2. On a scale of 1‐5 is your work mostly eco/epidemiological or evolutionary? 1 (100% eco/epidemiological) 3. On a scale of 1‐5 is your work mostly theoretical or experimental/empirical? 5 (100% empirical) Extraction du 10/5/2021 .