Genetic characterisation of fungal disease resistance genes in grapevine using molecular marker technology

[摘要] ENGLISH ABSTRACT: The aim of this study on grapevine was to genetically characterise, validate and map the reported fungal disease resistance genes of Pölöskei Muskotály (PM), Kishmish Vatkana (KV) and Villard Blanc (VB) in South Africa using QTL analysis. These fungal resistant parents were crossed with other varieties that have desirable fruit qualities in an effort to combine fungal disease resistance with desirable fruit qualities in a single variety. The genetic basis of PM's resistance to downy and powdery mildew has not been investigated before. It does however have VB in its pedigree so the assumption was made that the same QTL/genes present in VB contribute to this resistance. KV's resistance to powdery mildew reportedly originates from the REN1 gene located on chromosome 13. VB's powdery and downy mildew resistance is conferred by QTL present on chromosome 15 and chromosome 18 respectively and has been reported in numerous studies.The study populations comprised of 124 F1 PM x Regal Seedless plants, 16 F1 PM x G4-3418 plants, 14 F1 PM x Sunred Seedless plants, 158 F1 Sunred Seedless x KV plants and 250 F1 VB x G1-6604 plants. DNA was extracted from the leaves and all plants were screened using microsatellite markers. Phenotypic evaluations of downy and/or powdery mildew resistance were performed on the appropriate populations. The molecular data was used to generate linkage maps and combined with phenotypic data to perform QTL analysis.From the molecular data generated for the three PM populations it was determined that the F1 progeny inherited almost exclusively maternal alleles, and could not be used in a mapping study. These populations were eliminated from the study and PM will be used as a pollen donor in future. Molecular data from the Sunred Seedless x KV cross was used to generate a linkage map for chromosome 13 comprising eight markers and spanning 45.6 cM. When combined with the data from two powdery mildew phenotypic screens a QTL peak spanning the REN1 gene on chromosome 13 of KV was identified. This locus explains between 44.8% and 57.7% of the phenotypic variance observed. The molecular data from the VB x G1-6604 cross was used to generate partial linkage maps for chromosome 15 and 18. Eleven markers were mapped on chromosome 15 spanning 56.4 cM, and ten markers were mapped on chromosome 18 spanning 101.8 cM. When the chromosome 15 linkage map was combined with the data from two powdery mildew phenotypic screens a QTL associated with powdery mildew resistance was identified on chromosome 15 that explains between 18.9% and 23.9% of the phenotypic variance observed. Likewise a QTL associated with downy mildew resistance was identified on chromosome 18 when the chromosome 18 linkage map was combined with data from two downy mildew phenotypic screens. This QTL explains between 19.1% and 21.2% of the phenotypic variance observed.This study succeeded in genetically characterising the fungal disease resistance genes of two different sources of grapevine and provided exclusionary information on a third resistance source for future breeding applications.

[发布机构] Stellenbosch University