Isolation of RVI5 (VM) Locus from Malus × domestica 'Murray'

Scab resistance gene Rvi5 (Vm) is derived from Malus micromalus or Malus atrosanguinea 804 was introgressed into the apple variety ‘Murray’. This gene has the ability to induce a clear hypersensitive response after three days from Venturia inaqualis infection. Being ‘Murray’, a cultivar with an acceptable fruit quality compared to the old ancestors, this genotype could be used in breeding to pursue a durable resistance against Venturia inaequalis. This goal could be accomplished by two different approaches: resistance gene pyramiding by classical breeding or by a cisgenic approach, once the resistance gene will be identified. The isolation of the locus that harbors the resistance is an essential step toward the identification of the candidate genes. A pooling strategy enabled the identification of three overlapping Bacterial Artificial Chromosome (BAC) clones from a Murray library that are covering the Rvi5 region. Then, thanks to the availability of the Malus × domestica ‘Golden Delicious’ genome sequence, we were able to position the Rvi5 locus on the ‘Golden’ genome sequence in a region estimated of about 228 kbps in size. These three clones will be sequenced and assembled to obtain the complete sequence of Rvi5 locus. The assembled sequences will then be used for candidate gene identificatio