Identification of snp markers associated with resistance loci to downy mildew (Plasmopara viticola) disease in grapevine

Fungal diseases are one of the most important biotic stress factors in grape growing areas. By using 77 F1 populations obtained from Kyoho (resistant to P. viticola) and Yalova Pearl (susceptible to P. viticola) crosses, single nucleotide polymorphism (SNP) detection analyses and QTL mapping were performed and the QTLs controlling resistance to P. viticola, the mildew disease agent in grapes, were mapped in the grape genome. LOD values and percentage effect values calculated as a result of CIM analysis of SNP markers in the grape genome were calculated. As a result of the analyses, a total of 11 QTLs were determined to control resistance to P. viticola. Detailed polymorphism screening was performed by identifying SNPs. As a result of SNP analyses, it was determined that the strong QTLs associated with resistance were located on chromosomes 7, 14, 16 and 18 (1 on chromosome 7; 3 on chromosome 14; 1 on chromosome 16; 6 on chromosome 18), while QTLs located on a total of 4 chromosomes had minimum 29.3% and maximum 100% effect values. As a result of the studies, evaluations were made according to the sporulation intensity and sporulation area on the leaves after artificial inoculation of P. viticola. Inoculation scoring results, sporulation intensity and sporulation area (Boso et al. 2014; Uzun et al. 2018) results were evaluated according to 6 main classes. SNP markers showing linkage to QTLs were translated into 5 CAPS markers that can be used in MAS studies, and appropriate cutting enzymes were determined. Alphonse Lavellée x Regent and Yalova Pearl x Kyoho hybrid F1 genotypes were used for verification studies. Markers showed that no results could be obtained with a single primer since resistance to P. viticola is controlled by multiple genes. Therefore, it would be appropriate to re-run the PCR products obtained from Chr 14 SNP and Chr 16 SNP primers, which present a monomorphic band pattern, using systems that enable the separation of bands at very small bp distance. Chr 7 SNP could be evaluated and it was determined that the overlap rates of molecular tests with classical tests were 81% according to sporulation severity and 77% according to sporulation area.