## 3 Discussion  
### Natural Segregation Distortion Was Significant in F\({}_{2}\) Population  
The current VRS-F\({}_{2}\) GBS-rhAmpSeq integrated map includes markers that deviate from Mendelian segregation 1:2:1 ratio for chromosome 5, 7, 11, and 15. The addition of some of the distorted markers did not show any effect on marker order or recombination percentage, suggesting that marker segregation distortion is natural in these chromosomal regions for this F\({}_{2}\) grapevine population [39; 40]. The inclusion of these markers increased marker density and filled long gaps in the genetic map on chromosomes 5, 7, 11, and 15. Within the distorted regions, several reproductive related genes (multiple reproductive (Vitvi05g00109, Vitvi07g00910, Vitvi07g00921), male-sterility (Vitvi07g00807, Vitvi07g00814, Vitvi07g00822) and embryo development (Vitvi05g01066, Vitvi07g01429, Vitvi15g00642, Vitvi15g01065, Vitvi15g01084, Vitvi15g01085, Vitvi15g01122) were identified. Selection pressure operating against one of the parental alleles at meiosis cell division or zygote level has been suggested as a reason for natural segregation distortion in wheat [40]; however, it is not possible to determine whether this is a factor in this study. Segregation distortion can also be related to non-biological reasons, such as a small sampling population or genotype errors [41]. However, the mapping population size (514 individuals), advanced marker techniques, and the continuous blocks of segregation distortion suggest that biological, not technical, factors caused the segregation distortion in the VRS-F\({}_{2}\) population. Awareness of the distorted regions may help in planning crosses; however, further investigations are necessary to identify the mechanism(s) causing the segregation distortion.  
Figure 6: Genome-wide LOD for (E)-2-hexenal in 2013 (**A**) and 2018 (**B**). Black and red dashed line represent 1000 permutation at alpha of 0.1 and 0.05, respectively. (E)-2-hexenal averaged across 13 markers between peak positions for 2013 (**C**) and 2018 (**D**). _V. riparian_ ‘Manitoba 37’ grandparent (pistillate) is AA for all markers. ‘Seyval blanc’ (staminate) is BB for 11 markers and AB for 2 of the markers.  
The VRS-F\({}_{2}\) GBS-rhAmpSeq Integrated Map Provides Greater Marker Transferability to Other Populations  
Genetic maps play an important role in the identification of QTL, candidate genes, and marker assisted selection. Despite technological advances, low marker density and quality, high cost, and low marker transferability across populations remain as challenges in genetic map construction. Previous genetic maps for this VRS-F\({}_{2}\) grapevine population developed using SSR and GBS markers had large gaps in coverage [42; 43]. In this study rhAmpSeq markers, which have the potential of high marker transferability to other _Vitis_ germplasm, were used in combination with GBS markers to construct a high-density integrated genetic map for the interspecific F\({}_{2}\) population. The current integrated genetic map showed improvements over the previous GBS map for this population, with an increased marker density (74%) and increased genomic coverage. In addition, the inflated length of the previous GBS genetic map was reduced from 2424 to 1131 cM. Correlation with the _V. vinifera_ PN40024 12X V2 genome was higher than 98% for 18 of the 19 chromosomes in the integrated map. Chromosome 15 had lower correlation coefficient and coverage; however, this VRS-F\({}_{2}\) GBS-rhAmpSeq integrated map increased the chromosome 15 marker density (by 62% or 13 markers) relative to the previous GBS map [43]. The integrated map incorporates 1070 rhAmpSeq markers that were developed using multiple _Vitis_ species [8]. The rhAmpSeq markers identified for traits in this population can thus be used for marker-assisted selection if the GBS markers fail in other interspecific populations.