GrainGenes is a popular repository for information about genetic maps, mapping probes and primers, genes, alleles and QTLs for the following crops: wheat, barley, rye and oat. Documentation includes such data as primer sequences, polymorphism descriptions, genotype and trait scoring data, experimental protocols used, and photographs of marker polymorphisms, disease symptoms and mutant phenotypes. These data, curated with the help of many members of the research community, are integrated with sequence and bibliographic records selected from external databases and results of BLAST searches of the ESTs.