Sustainable resistances of roses to foliar diseases

The genetic determinism of partial and quantitative resistance in one genotype of R. wichurana was studied from three interconnected populations, and identified two major and stable QTLs on chromosomes 3 and 5. The interaction between R. wichurana and D. rosae was also studied at the histological and transcriptomic level. This work was carried out during the thesis of Diana Carolina Lopez Arias, defended in June 2021 .
In addition, a collection of monosporic strains of D. rosae was established. The genome sequences of two strains, one from modern rose, the other isolated from wild rose were used to develop microsatellite markers. A study of the genetic diversity of this collection was carried out and showed a structuring linked to the host (modern vs. wild). A characterization test for susceptibility/resistance in the greenhouse and on whole seedlings is available to characterize new varieties (projet Belarosa – Marolleau et al, 2020, Figure 1).

This theme is currently being developed through i) a Starter project (INRAe-BAP 2021-2022) GeRARD (Towards Genes for RosA Resistance to black spot Disease) whose objectives are to identify candidate genes and functions associated with the two main QTLs for resistance to black spot in R. hyb. wichurana and ii) an Ecophyto project (RoBIO - 2022-2024) whose objectives are to develop tools for characterizing the response of roses to different fungal diseases, and to implement a strategy for identifying biocontrol products, first in the laboratory, then in the greenhouse and finally in the field.

Figure 1: Resistance to black spot disease in rose. a) Development of an assay under controlled conditions to test fungal isolates b) Characterization of the genetic structuration of D. rosae strains collected from wild and cultivated roses (Marolleau et al, 2020). c) Detection of resistance QTLs to black spot disease on linkage group 3 by meta-analysis (Lopez-Ariaz et al, 2020)