Evaluation and Pre-selection of New Grapevine Genotypes Resistant to Downy and Powdery Mildew, Obtained by Cross-Breeding Programs in Spain

Variation in Susceptibility to Downy Mildew Infection in Spanish Minority Vine Varieties

Downy mildew is one of the most destructive diseases affecting grapevines (Vitis vinifera L.). Caused by the oomycete Plasmopara viticola (Berk. and Curt.) Berl. and de Toni, it can appear anywhere where vines are cultivated. It is habitually controlled by the application of phytosanitary agents (copper-based or systemic) at different stages of the vine growth cycle. This, however, is costly, can lead to reduced yields, has a considerable environmental impact, and its overuse close to harvest can cause fermentation problems. All grapevines are susceptible to this disease, although the degree of susceptibility differs between varieties. Market demands and European legislation on viticulture and the use of phytosanitary agents (art. 14 of Directive 128/2009/EC) now make it important to know the sensitivity of all available varieties, including minority varieties. Such knowledge allows for a more appropriate use of phytosanitary agents, fosters the commercial use of these varieties and thus increases the offer of wines associated with different terroirs, and helps identify material for use in crop improvement programmes via crossing or genetic transformation, etc. Over 2020-2021, the susceptibility to P. viticola of 63 minority vine varieties from different regions of Spain was examined in the laboratory using the leaf disc technique. Some 87% of these varieties were highly susceptible and 11% moderately susceptible; just 2% showed low susceptibility. The least susceptible of all was the variety Morate (Madrid, IMIDRA). Those showing intermediate susceptibility included the varieties Sanguina (Castilla la Mancha, IVICAM), Planta Mula (Comunidad Valenciana, ITVE), Rayada Melonera (Madrid, IMIDRA), Zamarrica (Galicia, EVEGA), Cariñena Roja (Cataluña, INCAVI), Mandrègue (Aragón, DGA) and Bastardo Blanco (Extremadura, CICYTEX). The highly susceptible varieties could be differentiated into three subgroups depending on sporulation severity and density.

DNA marker identification of downy mildew resistance locus Rpv10 in grapevine genotypes

One of the most common and harmful diseases of grapevine is downy mildew, caused by Plasmopara viticola. Cultivars of Vitis vinifera, the basis of high-quality viticulture, are mainly not resistant to downy mildew. Varieties with natural resistance to downy mildew belong to the vine species of North America and Asia (V. aestivalis, V. berlandieri, V. cinerea, V. labrusca, V. amurensis, etc.), as well as Muscadinia rotundifolia. The breeding of resistant cultivars is based on interspecific crossing. Currently, molecular genetic methods are increasingly used in pre-selection work and directly in breeding. One of the major loci of downy mildew resistance, Rpv10, was first identified in the variety Solaris and was originally inherited from wild V. amurensis. DNA markers that allow detecting Rpv10 in grapevine genotypes are known. We used PCR analysis to search for donors of resistance locus among 30 grape cultivars that, according to their pedigrees, could carry Rpv10. The work was performed using an automatic genetic analyzer, which allows obtaining high-precision data. Rpv10 locus allele, which determines resistance to the downy mildew pathogen, has been detected in 10 genotypes. Fingerprinting of grape cultivars with detected Rpv10 was performed at 6 reference SSR loci. DNA marker analysis revealed the presence of a resistance allele in the cultivar Korinka russkaya, which, according to publicly available data, is the offspring of the cultivar Zarya Severa and cannot carry Rpv10. Using the microsatellite loci polymorphism analysis and the data from VIVC database, it was found that Korinka russkaya is the progeny of the cultivar Severnyi, which is the donor of the resistance locus Rpv10. The pedigree of the grapevine cultivar Korinka russkaya was also clarified.