SEQUENCING OF THE PHYLLOXERA RESISTANCE LOCUS RDV1 OF CULTIVAR 'BÖRNER'

Abstract

Cultivar ‘Borner’, an interspecific cross of Vitis riparia Gm 183 and V. cinerea Arnold, is a phylloxera root resistant rootstock showing neither tuberosity nor nodosity symptoms. The Rdv1 locus, a major quantitative trait locus (QTL) localized on chromosome 13, correlates with the resistance phenotype. In order to identify the responsible gene(s) for this trait a high density genetic map was established for this region deducing STS markers from the V. vinifera genome sequence. For physical mapping a bacterial artificial chromosome (BAC) library was screened with the STS markers of the Rdv1 locus. The isolated clones were used to build up a minimal tiling path for the V. cinerea haplotype covering almost the entire locus. The BACs were sequenced, contigs assembled and finishing accomplished using the PN40024 genome sequence as a reference. Small final gaps were closed by sequencing of PCR products. Comparison of the 350 kb Rdv1 sequence with the V. vinifera sequence of PN40024 revealed a conserved gene order even for the small RGA cluster located in the middle of the sequence of both genomes. However, between these RGA clusters a low sequence homology and larger structural rearrangements within the RGAs and repetitive transposon fragments were observed. Therefore, the NBS-LRR-like genes located in the RGA cluster of the Rdv1 locus are favourable candidate genes for the phylloxera resistance of rootstock ‘Borner’.