| Summary: | Intraspecific diversity of the immune grape <i>Muscadinia rotundifolia</i> Michaux. can serve as a rich source of valuable resistance loci to the most widespread pathogens and pests of grapevine. While only one <i>Run1/Rpg1</i> resistance locus has been introgressed from <i>M. rotundifolia</i> to the <i>Vitis vinifera</i> gene pool, a number of other genes conferring resistance to powdery mildew and downy mildew have been identified in various <i>Muscadinia</i> cultivars. A larger introduction of <i>Muscadinia</i> varieties to the European continent would greatly facilitate experiments of interspecific crosses as well as stimulate biotechnological efforts to overcome the main barrier to F1 fertility caused by the differences in chromosome number. For the successful introduction of <i>Muscadinia</i> into the new European environment, it is necessary to overcome the difficulties associated with the physiological characteristics of the species, such as insufficient cold tolerance and very late fruit ripening. To facilitate the further discovery of valuable loci in <i>Muscadinia</i> and their transfer to grapevine breeding programs, we constructed a high-density linkage map using an S1 mapping population obtained from the self-pollination of <i>M. rotundifolia</i> cv. Dixie maintained on the southern coast of Crimea. Using ddRADseq, 3730 SNPs were ordered across 20 linkage groups spanning 2753.6 cM of the total map length. No segregation in resistance to diseases and pests was observed among the ‘Dixie’ S1 population, suggesting the presence of homozygous non-segregating resistant loci in the genetic background of ‘Dixie’. Markers with high segregation distortion showed a bias towards chromosomal intervals on linkage groups 10 and 20, where loci affecting the survival of ‘Dixie’ S1 progeny may be localized. QTLs with significant additive and dominance effects were discovered on LG14 and LG18, affecting the morphological traits associated with the vigor of growth and adaptability of young <i>Muscadinia</i> vines in the conditions of Crimea.
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