ABSTRACT
Intraspecific diversity of the immune grape Muscadinia rotundifolia Michaux. can serve as a rich source of valuable resistance loci to the most widespread pathogens and pests of grapevine. While only one Run1/Rpg1 resistance locus has been introgressed from M. rotundifolia to the Vitis vinifera gene pool, a number of other genes conferring resistance to powdery mildew and downy mildew have been identified in various Muscadinia cultivars. A larger introduction of Muscadinia 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 Muscadinia 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 Muscadinia 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 M. rotundifolia 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 Muscadinia vines in the conditions of Crimea.
ABSTRACT
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 Vitis interspecific hybrid 'Magarach 31-77-10' as a female parent and Muscadinia rotundifolia × Vitis vinifera 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 Run1/Rpv1 locus inherited from M. rotundifolia. 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 (âM. 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.
