The Assessment of Agrobiological and Disease Resistance Traits of Grapevine Hybrid Populations (<i>Vitis vinifera</i> L. × <i>Muscadinia rotundifolia</i> Michx.) in the Climatic Conditions of Crimea

The Crimean autochthonous grape varieties are unique by their origin and serve as a valuable source for breeding new cultivars with increased salt and frost resistance, as well as high-quality berries. However, they suffer from fungal pathogens, as the dry and hot summer months contribute to the epiphytotic course of diseases. An increase in the resistance of Crimean grape varieties is currently achieved through interspecific hybridization. In this study, we describe the genetic and agrobiological diversity of three hybrid populations obtained using the <i>Vitis</i> interspecific hybrid ‘Magarach 31-77-10′ as a female parent and <i>Muscadinia rotundifolia</i> × <i>Vitis vinifera</i> BC5 hybrid plants as male parents. The hybrid nature of the populations was assessed using RADseq high-throughput genotyping. We discovered 12,734 SNPs, which were common to all three hybrid populations. We also proved with the SSR markers that the strong powdery and downy mildew resistance of the paternal genotypes is determined by the dominant <i>Run1/Rpv1</i> locus inherited from <i>M. rotundifolia</i>. As a result, the disease development score (R, %) for both mildew diseases in the female parent ‘Magarach 31-77-10’ was three times higher than in male parents 2000-305-143 and 2000-305-163 over two years of phytopathological assessment. The highest values of yield-contributing traits (average bunch weight ~197 g and 1.3 kg as yield per plant) were detected in the population 4-11 (♀M. No. 31-77-10 × 2000-305-163). Despite the epiphytotic development of PM, the spread of oidium to the vegetative organs of hybrids 4-11 did not exceed 20%. Some hybrid genotypes with high productivity and resistance to pathogens were selected for further assessment as promising candidates for new varieties.