Breeding for black rot resistance in grapevine: advanced approaches for germplasm screening

Crop improvement by means of traditional or molecular breeding is a key strategy to accomplish the European Green Deal target of reducing pesticides by 50% by 2030. Regarding viticulture, this is exacerbated by the massive use of chemicals to control pathogen infections. Black rot is an emergent disease caused by the ascomycete Phyllosticta ampelicida, and its destructiveness is alarming vine growers. Implementing and improving effective phenotyping strategies are fundamental preliminary steps to breed disease resistant varieties and this work suggests good practices adopted for this purpose. Primarily, the pedigree of black rot resistance donors was reconstructed based on the collection of phenotypic historical data, highlighting unexplored sources of black rot resistance. Strains used for artificial infections were isolated, genetically characterized and mixed to avoid race-specific resistance selection. A new inoculation protocol based on the use of leaf mature lesions was developed. Ex vivo inoculation on detached leaves was effective for the evaluation of conidia germination and hyphal growth, but not for disease progression. Finally, the pedigree was used for the identification of 23 genotypes to be tested. Two breeding selections (NY39 and NY24) resulted symptomless in all assessments and a third one (F25P52) also showed very high resistance, although with a greater variability. Other two genotypes (F12P19 and ‘Charvir’) fell within the medium resistance category, making them good candidates in a regime of well-timed preventive treatments. In conclusion, this work was effective to a comprehensive parental line characterization and preparatory towards grapevine breeding programs for black rot resistanc

Genome Sequences of Both Organelles of the Grapevine Rootstock Cultivar ‘Börner’

Frommer B, Holtgräwe D, Hausmann L, et al. Genome Sequences of Both Organelles of the Grapevine Rootstock Cultivar ‘Börner’. Microbiology Resource Announcements. 2020;9(15): e01471-19.Genomic long reads of the interspecific grapevine rootstock cultivar ‘Börner’ (Vitis riparia GM183 × Vitis cinerea Arnold) were used to assemble its chloroplast and mitochondrion genome sequences. We annotated 133 chloroplast and 172 mitochondrial genes, including the RNA editing sites. The organelle genomes in ‘Börner’ were maternally inherited from Vitis riparia

QTL analysis of flowering time and ripening traits suggests an impact of a genomic region on linkage group 1 in Vitis.

Fechter I, Hausmann L, Zyprian E, et al. QTL analysis of flowering time and ripening traits suggests an impact of a genomic region on linkage group 1 in Vitis. Theoretical and Applied Genetics. 2014;127(9):1857-1872.In the recent past, genetic analyses of grapevine focused mainly on the identification of resistance loci for major diseases such as powdery and downy mildew. Currently, breeding programs make intensive use of these results by applying molecular markers linked to the resistance traits. However, modern genetics also allows to address additional agronomic traits that have considerable impact on the selection of grapevine cultivars. In this study, we have used linkage mapping for the identification and characterization of flowering time and ripening traits in a mapping population from a cross of V3125 ('Schiava Grossa' × 'Riesling') and the interspecific rootstock cultivar 'Börner' (Vitis riparia × Vitis cinerea). Comparison of the flowering time QTL mapping with data derived from a second independent segregating population identified several common QTLs. Especially a large region on linkage group 1 proved to be of special interest given the genetic divergence of the parents of the two populations. The proximity of the QTL region contains two CONSTANS-like genes. In accordance with data from other plants such as Arabidopsis thaliana and Oryza sativa, we hypothesize that these genes are major contributors to control the time of flowering in Vitis

A Partially Phase-Separated Genome Sequence Assembly of the Vitis Rootstock ‘Börner’ (Vitis riparia × Vitis cinerea) and Its Exploitation for Marker Development and Targeted Mapping

Holtgräwe D, Rosleff Soerensen T, Hausmann L, et al. A Partially Phase-Separated Genome Sequence Assembly of the Vitis Rootstock ‘Börner’ (Vitis riparia × Vitis cinerea) and Its Exploitation for Marker Development and Targeted Mapping. Frontiers in Plant Science. 2020;11: 156.Grapevine breeding has become highly relevant due to upcoming challenges like climate change, a decrease in the number of available fungicides, increasing public concern about plant protection, and the demand for a sustainable production. Downy mildew caused by Plasmopara viticola is one of the most devastating diseases worldwide of cultivated Vitis vinifera. In modern breeding programs, therefore, genetic marker technologies and genomic data are used to develop new cultivars with defined and stacked resistance loci. Potential sources of resistance are wild species of American or Asian origin. The interspecific hybrid of Vitis riparia Gm 183 x Vitis cinerea Arnold, available as the rootstock cultivar ‘Börner,’ carries several relevant resistance loci. We applied next-generation sequencing to enable the reliable identification of simple sequence repeats (SSR), and we also generated a draft genome sequence assembly of ‘Börner’ to access genome-wide sequence variations in a comprehensive and highly reliable way. These data were used to cover the ‘Börner’ genome with genetic marker positions. A subset of these marker positions was used for targeted mapping of the P. viticola resistance locus, Rpv14, to validate the marker position list. Based on the reference genome sequence PN40024, the position of this resistance locus can be narrowed down to less than 0.5 Mbp on chromosome 5