S05 - Session O2 - Histological and transcriptomic characterization of a partial resistance in the rose-Diplocarpon rosae interaction

Authors: Diana Carolina Lopez Arias, Sophie Paillard, Laurence Hibrand-Saint Oyant, Thomas Debener, Marcus Linde, Aurélia Rolland, Fabienne Simonneau, Fabrice Foucher, Vanessa Soufflet-Freslon *

Black spot, caused by the fungus Diplocarpon rosae , is the most important foliar disease in cultivated garden roses. With the reduction and in some cases the prohibition of agrochemical use (Ecophyto plan in France), the development of resistant roses is essential. So far, research has mainly focused on the study of major genes, but this type of resistance is known to be less durable. Partial resistance to black spot disease was described in Rosa wichurana (RW) genotypes. We showed that RW partial resistance is mainly controlled by two quantitative trait loci located on linkage groups B3 and B5. To dissect the mechanisms underlying such resistance, two complementary approaches were taken. Artificial inoculation on whole plants in the greenhouse and on detached leaves in the laboratory allowed us to undertake a detailed study of RW resistance at macroscopic and microscopic levels as well as to investigate the importance of leaf age for partial resistance to the black spot disease. Besides, we proceeded to a comparative study of the transcriptomic changes that happen during the infection process using a time course approach with a multi-series experiment on whole plants under greenhouse conditions. The RW defense response was characterized as following: first, a quick immune response (PTI) leads to the activation of genes involved in callose deposition in papillae, and then an effector specific response (ETI) results in a HR. These results pave the way for marker-assisted selection and for gene cloning.