Plant & Animal Genome IX Conference

Workshop: Fruit/Nut Tree
W27_01.html

IDENTIFICATION AND CHARACTERIZATION OF A RECEPTOR-LIKE GENE CLUSTER FROM THE VF SCAB RESISTANCE LOCUS IN APPLE

¹ Dipartimento di Colture Arboree, University of Bologna, 40126 Bologna, Italy

² Plant Pathology Group, Institute of Plant Sciences, Swiss Federal Institute of Technology, 8092 Zürich, Switzerland

³ Department of Soil and Crop Sciences, Texas A&M University, College Station, TX 77840, USA

Vf scab resistance of Malus floribunda 821 is the most widely used scab resistance source in apple breeding. However, no scab resistant apple variety has yet conquered the market due to the lack of high enough fruit quality compared to the most successful scab susceptible varieties. Therefore, cloning the Vf resistance gene and using it in transformation of high quality apple varieties would be an advantage. We have previously reported the construction of a high-density genetic map around the Vf locus, the physical mapping of the Vf locus, and the construction of a BAC contig covering the Vf locus. Here we report the identification of candidate Vf genes from the BAC contig. The most promising candidate genes are represented by a cluster of receptor-like genes with homology to the Cf (Cladosporium fulvum) resistance gene family of tomato. Three members of the cluster, named HcrVf1, HcrVf2 and HcrVf3 (Homologues of Cladosporium fulvum resistance genes of the Vf-region), were completely sequenced. The deduced amino acid sequences coded by these genes contain an extra-cellular leucine-rich repeat domain and a trans-membrane domain. We have analyzed their expression by RT-PCR and shown that two of the genes are constitutively expressed and one gene is a non-expressed pseudo-gene. We have cloned some of the BAC clones containing the Cf homologs into binary vectors and are now using them for transformation of scab susceptible apple cultivars.