Proceedings of the XLVII Italian Society of Agricultural Genetics - SIGA Annual Congress

Verona, Italy - 24/27 September, 2003

ISBN 88-900622-4-X

Poster Abstract - 2.31

SYNTENY RELATIONSHIPS WITH RICE AND TIGHT ASSOCIATION WITH RESISTANCE GENE ANALOGS WAS REVEALED BY THE FINE MAPPING OF THE BARLEY LEAF STRIPE RESISTANCE GENE Rdg2a

D. BULGARELLI*, N. COLLINS**, G. TACCONI*, E. DELLAGLIO*, M. BARAVELLI*, G. TUMINO*, A.M. STANCA*, G. VALÈ*

*) Istituto sperimentale per la Cerealicoltura, Sezione di Fiorenzuola d’Arda, Via S. Protaso 302, 29017 Fiorenzuola d’Arda, Italy

**) Sainsbury Laboratory, John Innes Centre, Norwich, NR4 7UH, UK

barley, leaf stripe, resistance gene analogs, synteny

The single, dominant gene Rdg2a of barley, which confers resistance to the seed-borne pathogen Pyrenophora graminea, is located in the distal region of chromosome 7H. As the first step towards the isolation of the gene, an high resolution genetic map in the region of the Rdg2a locus was constructed by saturation mapping of a large segregating F2 population of 1400 plants (ThibautRdg2a x Mirco). CAPS markers closely associated to the gene were identified. As additional source of markers (and as putative Rdg2a-candidates), also six resistance gene analogs (RGAs), known to map in this chromosomal region, were mapped. The resistance gene Rdg2a was delimited in a genetic interval of 0.18 cM between the RFLP marker ssCH4 and the CAPS markers MWG851. ssCH4 was separated from the resistance gene by two recombination events (0.07 cM), while MWG851 by three recombination events (0.1 cM); both these markers are RGAs. Other RGAs were found to be in linkage with the gene, supporting that this chromosomal region is rich in NBS-LRR sequences. Rice expressed sequences (ESTs) mapped to the distal region of the chromosome 6 were exploited to identify homologs in barley or wheat ESTs and PCR-based markers were developed and mapped; a syntenic relationship with rice was subsequently identified. Markers flanking Rdg2a, derived from rice ESTs information, genetically delimited a contiguous set of a 115 kb rice PAC clones within which any homologous sequences to characterized resistance gene were identified. Thus, either the Rdg2a-homologs gene is not present in rice or the gene is not in a syntenic location.