Title : Evaluation of resistance to foliar diseases of selected genotypes of V. vinifera x Vitis ssp resistant crosses
Abstract:
Powdery mildew, caused by the ascomycete Erysiphe necator, and downy mildew, caused by the oomycete Plasmopara viticola, are the main diseases affecting grapevines, leading to significant economic losses in the viticulture sector worldwide. Their control accounts for a high percentage of the annual applications of phytosanitary products used in viticulture, with the consequent negative impact on the environment, including the reduction of the biodiversity of the viticultural ecosystem, and the appearance of resistances that make these products less and less effective. The European Green Pact prioritizes the protection and preservation of the environment, and imposes increasing restrictions on the use of these products. In this context, the development of disease-resistant grapevine varieties, obtained through crosses of Vitis vinifera with other resistant species of the Vitis genus, is an alternative for achieving sustainable viticulture. To ensure effective and long-lasting resistance, it is necessary to incorporate multiple resistance genes into the same plant, so that they can provide different defense mechanisms against the pathogen. In this direction, in the Breeding Program developed at the IMIDA, 27 genotypes from crosses between ?(Monastrell x Regent) x Kishmish vatkana] (MRomK) and ?(Monastrell x Regent) x Solaris? (MRomS) were preselected by marker-assisted selection (MAS), using primers specific for the resistance genes introgressed for the presence of loci Ren1, Ren3, Ren9, Rpv3 and Ren3; Ren9; Rpv3; Rpv10, respectively. The objective of this study was to evaluate the resistance of selected hybrids to powdery mildew and downy mildew by in vitro inoculation assays. This objective is framed within the Shield 4 Grape project (HORIZON-CL6-2023-BIODIV-01-14). Young leaves, previously sterilized, were inoculated with a vacuum tower for powdery mildew and by dilution (105 cfu/ml) for downy mildew. Fungal development was evaluated at 7 and 14 days after inoculation on a scale of 0 to 5 for powdery mildew, and on a scale of 1 to 9 (OIV descriptor 452) for downy mildew. On average, the MRomK genotypes presented a higher level of resistance to powdery mildew than the MRomS family, unlike the downy mildew, where the MRomS family showed a higher level of resistance. The genotypes selected for their resistance, higher than that of their resistant parents, were MRomS1, MRomS7 and MRomS16 for both diseases, and MRomS5, MRomS6, RomS16, RomS17 and MRomS22 for powdery mildew, and MRomK5, MRomK8, MRomK9, MRomK20, RomK24 and MRomK28 for downy mildew. The next step of this work will be to evaluate these genotypes for their agronomic and oenological aptitudes.
