Format: ORAL

Rosala Pieiro1, Lowana Cahn2, Katharina B. Budde3, Agathe Hurel4, Adelaide Theraroz2, Giovanni G. Vendramin5, Sara Pinosio5, Marina de Miguel6, Christophe Plomion2, Myriam Heuertz2, Santiago C. Gonzlez-Martnez2

1 Evolutionary Biology Research Group (GIBE), Interdisciplinary Centre of Chemistry and Biology (CICA), University of A Coruña, Campus da Zapateira sn. 15071 A Coruña, Spain 2 INRAE, Univ. Bordeaux, BIOGECO, F-33610 Cestas, France 3 North West German Forest Research Institute, Department of Forest Genetic Resources, Professor-Oelkers-Strasse 6, 343446 Hann Münden, Germany 4 Department of Forest Growth, Silviculture and Genetics, Unit of Genome Research, Austrian Research Centre for Forests, A-1131 Wien, Seckendorff-Gudent-Weg 8, Austria 5 Institute of Biosciences and BioResources, National Research Council of Italy, Division of Firenze, via Madonna del Piano 10, 50039 Sesto Fiorentino, Italy 6 EGFV, Univ. Bordeaux, Bordeaux Sciences Agro, INRAE, ISVV, 33882, Villenave d’Ornon, France

Genetic load, i.e., the accumulation of deleterious mutations in the genome, is predicted to cause a reduction in individual fitness. In plants, an increased number of deleterious mutations has been documented as a consequence of population bottlenecks, for instance in small or recently colonised populations at the margin of species ranges, or in cultivated plants as a negative outcome of domestication. However, the actual adverse effect of genetic load on plant phenotypes remains virtually uncharacterised. We estimated genetic load in populations of the Atlantic-Mediterranean conifer maritime pine, Pinus pinaster Aiton, to examine its association with phenotypic traits related to growth and phenology (budburst) measured under common garden conditions. We observed a strong negative correlation between genetic load and tree height on the island of Corsica based on two different datasets (including 133,656 SNPs in 393 individuals and 10,185 SNPs in 334 individuals), thus suggesting a negative effect of the accumulation of deleterious alleles on tree growth on the regional scale. This association was further confirmed by a wide-range analysis including 464 individuals from 34 populations across the entire range of maritime pine in the western Mediterranean, Atlantic Europe and North Africa. Our study is one of the first to experimentally demonstrate adverse phenotypic effects of genetic load in a long-lived plant.