Comic-Sammelband

Due to adventive grapevine pathogens like Plasmopara viticola, variable problems in European viticulture such as yield loss and the high usage of plant protection still occur. For that reason many breeders invest hope in cultivating fungi-resistant varieties using American and Asian wild species as resistance donor in new crosses. Several resistance loci against P. viticola were identified from different working groups so far. By facing the possibility of P. viticola strains to overcome resistances, quantitative trait loci (QTL) analysis was used in this work to screen for new resistance loci in two cross populations. Hereby a major QTL (Rpv10.2) as well as several minor QTLs were detected. The calculation of the QTLs was based on phenotypic data obtained from infections tests and the creation of linkage maps of the cross populations ‘Tigvoasa’ x We 90-06-12 (TVxWe90) und ‘Cabernet Franc’ x ‘Triomphe d‘Alsace’ (CFxTA). Simple sequence repeat (SSR) and RNase H2-dependent amplicon sequencing (rhAmpSeq) markers were used to create the linkage maps. Rpv10.2 was identified as resistance locus by a major QTL on linkage group 09 in the genome of We90. The locus was introgressed by the resistant cultivar We 90-06-12, which derives from the Asian wild grape Vitis amurensis. The area of Rpv10.2 was restricted by the SSR-markers GF09-65 and GF09-47 to approximately 80 kb on the V. vinifera reference genome. This area matches the already identified Rpv10 locus from ‘Solaris’, which also derived from V. amurensis (Schwander et al. 2012). Based on microscopic observation of infected leaf samples, We 90-06-12 and ‘Solaris’ showed similar reaction of resistance to inhibit the growth of P. viticola hyphae. The putative candidate gene RPS5-like is suspected to stay in connections with the Rpv10-mediated resistance ‘Solaris’ (Zyprian et al., in preparation). Due to sequence analysis, the corresponding gene could be verified in We 90-06-12 without any differences. In comparison, a further candidate gene AP2-ERF-like showed a variation in the coding sequence. The variation was observed outside the functional area of the AP2 protein domain. In addition marker analysis repeatedly showed deviating data for We 90-06-12 regarding GF09-46 and GF09-48, which are markers used in breeding since many years to identify new cultivars carrying the Rpv10 locus. The results of this work give evidence for an Rpv10 haplotype defined as Rpv10.2, which can be used for breeding. Rpv10.2 can be distinguished from the Rpv10 locus by the markers GF09-68, GF09-46 and GF09-48. The findings of this work can be used for further characterization of the Rpv10.2 locus in the future. In case of population CFxTA multiple weak QTLs were detected. Those QTLs could only be reproduced for linkage group 12 and 17. The areas of the QTLs on those groups cover long distances on the V. vinifera reference genome. It is necessary to obtain additional marker data to point out if these QTLs are suitable for breeding. It should be mentioned that until now no resistance loci were detected on linkage group 17. In comparison, Rpv6 was detected on linkage group 12 (Marguerit et al. 2009). ‘Riparia Gloire de Montpellier’, a selection of the American wild grape Vitis riparia, was recognized as the origin of this locus. The variety ‘Triomphe d’Alsace’, which represents the resistance donor in case of the cross CFxTA, originates from ‘Riparia Gloire de Montpellier’. If the detected QTL on linkage group 12 is identical to the Rpv6 locus should be verified by further investigations. This work indicates that the resistance level decreases from ‘Riparia Gloire de Montpellier’ to ‘Triomphe d’Alsace’. The hypersensitive response (HR) shown by the cultivar ‘Triomphe d’Alsace’ is weaker compared to ‘Riparia Gloire de Montpellier’ and matches with the identification of multiple weak QTLs in the population CFxTA.

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