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Identification of R-Gene Homologous DNA Fragments Genetically Linked to Disease Resistance Loci in Arabidopsis thaliana

¹Department of Molecular Biology, DLO-Centre for Plant Breeding and Reproduction Research, Postbus 16, 6700 AA Wageningen, The Netherlands; ²Plant Pathology and Weed Science Department, Horticultural Research International-Wellesbourne, Warwickshire CV35 9EF, U.K.; ³Department of Biological Sciences, Wye College, University of London, Wye, Ashford, Kent TN25 5AH, U.K.

Disease resistance in plants is a desirable economic trait. A number of disease resistance genes from various plant species have been cloned so far. The gene products of some of these can be distinguished by the presence of an N-terminal nucleotide binding site and a C-terminal stretch of leucine-rich repeats. Although these gene products are structurally related, the DNA sequences are poorly conserved. Only parts of the nucleotide binding site share enough DNA identity to design primers for polymerase chain reaction amplification of related DNA sequences. Such primers were used to amplify different resistance-gene-like (RGL) DNA fragments from Arabidopsis thaliana accessions Landsberg erecta and Columbia. Almost all cloned DNA fragments were genetically closely linked with known disease resistance loci. Most RGL fragments were found in a clustered or dispersed multi-copy sequence organization, supporting the supposed correlation of RGL sequences and disease resistance loci.