S02 - Session O5 - Adapting stone fruit to pesticide reduction: screening apricot and peach core-collections for multi-pest resistance via integrative phenotyping under low pesticide management

Authors: Marie Serrie *, Véronique Signoret , Alain Blanc, Laurent Brun, Frédéric Gilles, Sabrina Viret, Freddy Combe, Guillaume Roch, Guy Clauzel, Jean-Marc Audergon, Bénédicte Quilot-Turion, Morgane Roth

Stone fruit production must address an urgent societal and environmental demand for pesticide reduction and has to face unexpected epidemiological changes because of climate change. Cultivar improvement is a promising strategy to operate a sustainable transition towards low phytosanitary management. However, to date we lack varieties bearing one or more resistances against pests and diseases and genetic resources are underused. To tackle this issue, two core-collections, composed of 150 apricot and 206 peach replicated accessions, have been set up. These collections have been densely genotyped and have been planted respectively in two and three sites along a North-South gradient between Valence and Perpignan (France), between 2017 and 2019. These orchards are managed under low phytosanitary protection to observe the damages of pests and diseases present in natural conditions. Phenological variables are also relevant, because they are potential epidemiological covariates. Thus, in these young orchards we have monitored three phenological traits of interest: blooming date, vegetative bud break and flower density. We observed wide phenotypic diversity for these preliminary traits within the orchards, which illustrates the high genetic diversity represented in our core-collections. Moreover, we observed quite high values of broad sense heritability (between 0.67 and 0.90). Finally, we identified a strong effect of the environment and of genotype by environment interactions. The study of these traits highlights the importance of a multi-site design to account for these different effects. To our knowledge, our multisite design, which is deployed with the objective of studying the multiple resistances to pests and diseases in apricot and peach, is the first of such amplitude. This project paves the way for future genome-wide association studies aiming at identifying candidate genes for multiple resistances as well as marker assisted selection.