ALLELE MINING AT THE LOCUS GRO 1 IN SOLANUM WILD SPECIES

The variability of one cluster of genes at the Gro 1 locus was studied in several potato species. The cluster is known to comprise 10 different alleles, among which only the Gro 1-4 gene had been demonstrated to confer disease resistance. Using sequence information available at EMBL/GenBank/DDBJ databases (accession numbers AY196151-AY196163), we have designed three primer pairs that target different regions of the Gro 1 sequence. The first was designed in a highly conserved region and allowed the presence of at least one member of the gene cluster to be identified in 16 wild species analysed. The second primer pair was designed on a Gro 1-4 specific region and its use demonstrated that no gene identical to Gro 1-4 was present in any wild potato species analysed. Finally, the major part of the LRR coding sequence of the Gro 1 gene was also amplified and sequenced in 16 wild species. In total, 409 SNPs were identified, varying from 12 SNPs in Solanum demissum to 35 in S. stoloniferum. The non-synonymous/synonymous ratio (Ka/Ks) in most species was different from 1, suggesting that the gene is under selective pressure. The alignment of translated sequences was compared to the Gro 1-4 gene from GenBank (AY196151). Polymorphisms were found and classified in regard to the position of amino acid substitutions and to the nature of amino acids involved. Substitutions of L amino acids were 80% conservative, while substitutions of amino acids exposed to solvents were 45% non-conservative.