Research article

A physical map of the heterozygous grapevine 'Cabernet Sauvignon' allows mapping candidate genes for disease resistance

Marco Moroldo^1* , Sophie Paillard^1,2* , Raffaella Marconi³ , Legeai Fabrice⁴ , Aurelie Canaguier¹ , Corinne Cruaud⁵ , Veronique De Berardinis⁵ , Cecile Guichard¹ , Veronique Brunaud¹ , Isabelle Le Clainche¹ , Simone Scalabrin^6,7 , Raffaele Testolin^3,7 , Gabriele Di Gaspero^3,7 , Michele Morgante^3,7 and Anne-Francoise Adam-Blondon¹

¹  UMR de Génomique Végétale, INRA-CNRS-UEVE, 2, Rue Gaston Crémieux, CP5708, 91057 Evry Cedex, France

²  UMR118, INRA-Agrocampus, University of Rennes, Amélioration des Plantes et Biotechnologies Végétales, F-35650 Le Rheu, France

³  Dipartimento di Scienze Agrarie e Ambientali, University of Udine, via delle Scienze 208, 33100 Udine, Italy

⁴  Unité de Recherche Génomique-Info, URGI, Tour Evry 2, 523, Place des Terrasses de l'Agora, 91034 Evry Cedex, France

⁵  Gnoscope, 2, rue Gaston Crémieux, CP5706, 91057 Evry Cedex, France

⁶  Dipartimento di Scienze Matematiche, University of Udine, via delle Scienze 208, 33100 Udine, Italy

⁷  Istituto di Genomica Applicata, Parco Scientifico e Tecnologico Luigi Danieli, via Jacopo Linussio 51, 33100 Udine, Italy

author email corresponding author email* Contributed equally

BMC Plant Biology 2008, 8:66doi:10.1186/1471-2229-8-66

Published:	13 June 2008

Abstract

Background

Whole-genome physical maps facilitate genome sequencing, sequence assembly, mapping of candidate genes, and the design of targeted genetic markers. An automated protocol was used to construct a Vitis vinifera 'Cabernet Sauvignon' physical map. The quality of the result was addressed with regard to the effect of high heterozygosity on the accuracy of contig assembly. Its usefulness for the genome-wide mapping of genes for disease resistance, which is an important trait for grapevine, was then assessed.

Results

The physical map included 29,727 BAC clones assembled into 1,770 contigs, spanning 715,684 kbp, and corresponding to 1.5-fold the genome size. Map inflation was due to high heterozygosity, which caused either the separation of allelic BACs in two different contigs, or local mis-assembly in contigs containing BACs from the two haplotypes. Genetic markers anchored 395 contigs or 255,476 kbp to chromosomes. The fully automated assembly and anchorage procedures were validated by BAC-by-BAC blast of the end sequences against the grape genome sequence, unveiling 7.3% of chimerical contigs. The distribution across the physical map of candidate genes for non-host and host resistance, and for defence signalling pathways was then studied. NBS-LRR and RLK genes for host resistance were found in 424 contigs, 133 of them (32%) were assigned to chromosomes, on which they are mostly organised in clusters. Non-host and defence signalling genes were found in 99 contigs dispersed without a discernable pattern across the genome.

Conclusion

Despite some limitations that interfere with the correct assembly of heterozygous clones into contigs, the 'Cabernet Sauvignon' physical map is a useful and reliable intermediary step between a genetic map and the genome sequence. This tool was successfully exploited for a quick mapping of complex families of genes, and it strengthened previous clues of co-localisation of major NBS-LRR clusters and disease resistance loci in grapevine.