157 Screening Grape Hybrid Families with Molecular Markers Linked to Resistance Genes D. Katula-Debreceni 1 , A. Szőke 1 , A.K. Lencsés 1 , E. Kiss 1 , P. Kozma 2 , S. Hoffmann 2 , A. Veres 1 and L. Kovacs 3 1 Szent István University, Institute of Genetics and Biotechnology, Gödöllő, Hungary 2 Research Institute of Viticulture and Enology, Pécs, Hungary 3 Missouri State University, Department of Biology, Springfield, Missouri, USA Keywords: powdery mildew, downy mildew, durable disease resistance, REN1, RUN1, RPV1, MAS Abstract Gene pyramiding is a potential method to breed new grape cultivars with durable disease resistance. The use of resistance gene-linked DNA markers consider- ably reduces the volume of breeding experiments, since it makes possible the identifi- cation of progeny seedlings that have inherited the desired gene shortly after germination, and permits the reduction of population size. Saturating the grape genome with molecular markers, the construction of genetic linkage maps and the recent publication of the Vitis vinifera genome sequence allow for the direct selection the desired genotype. To combine powdery and downy mildew resistance genes Kozma et al. (Research Institute of Viticulture and Enology, Pécs) made the following crosses: ‘BC 4 ’ (‘VRH 3082-1-42’) × V. vinifera ‘Kishmish vatkana’, ‘BC 4 ’ × V. vinifera ‘Kishmish moldavskiy’, V. vinifera ‘Génuai zamatos’ × V. vinifera ‘Kishmish vatkana’, (‘Lasta’ × V. vinifera ‘Dzhandzhal kara’) × (V. vinifera ‘Katta kurgán’ × V. vinifera ‘Perlette’). Our aim was to select individuals containing powdery (PM) and/or downy mildew (DM) major resistance genes of different origin (Muscadinia rotundifolia-RUN1, RPV1, V. vinifera-REN1, and PM and DM QTLs of Seyve-Villard) with SSR markers. We compared the symptomless progenies derived from the cross ‘BC 4 ’ × ‘Kishmish vatkana’ and (‘Lasta’ × ‘Dzhandzhal kara’) × (‘Katta kurgán’ × ‘Perlette’) using resistance linked markers. We observed that alleles of SSR markers linked to the PM resistance gene REN1 in the linkage group 13 are the same, so the PM resistance genes of ‘Kishmish vatkana’ and ‘Dzhandzhal kara’ appear identical. INTRODUCTION Incorporating durable resistance to the most important fungal diseases (powdery and downy mildew, PM and DM) into cultivars of excellent quality has become a crucial objective of European grapevine breeding since the second half of the 19 th century when these pathogens were imported from North America into Europe. Different resistance (R) genes are thought to detect the pathogen by different mechanisms, therefore, resistance conferred by a combination of various R genes is more difficult to overcome by the pathogen than resistance due to a single R gene (McDonald and Linde, 2002). Intro- gression of resistance genes from wild Vitis species is one possible way to achieve resistance or increased tolerance in susceptible V. vinifera L. cultivars. Since no V. vinifera cultivars carrying major PM resistance genes were found till the mid 1960s, wild Vitis species were utilized as resistance gene sources. Because of their low quality many crosses to V. vinifera are required in order to recover high quality vinifera cultivars (Fischer et al., 2004). In Hungary, resistance breeding started in 1949 aiming to produce powdery and downy mildew resistant cultivars. For this purpose, at the beginning French- American hybrids were used (Kozma jr., 1999). Crossing of the mildew resistant ‘Villard blanc’ cultivar resulted in cultivars in which resistance and high quality coexist: e.g., ‘Zalagyöngye’, ‘Bianca’, ‘Medina’, ‘Nero’ (Csizmazia and Bereznai, 1968). However, many wild Vitis species carry high or partial resistance to pathogens. Muscadinia rotundifolia MICH. SMALL was described as totally resistant to PM and DM (Boubals, Proc. X th Intl. Conf. on Grapevine Breeding and Genetics Eds.: B.I. Reisch and J. Londo Acta Hort. 1046, ISHS 2014