Localization of QTLs and candidate genes involved in the regulation of frost tolerance in cereals

The recent advances in the molecular investigation of the stress response have led to the identification of a great number of genes whose expression is associated to cold acclimation. In the model species Arabidopsis thaliana, a crucial role in the regulation of the gene set involved in cold tolerance has been clearly demonstrated for a family of transcription factors named C-repeat binding factor (CBF). Genes similar to the Arabidopsis CBF genes were identified in the EST database of many crop species including barley and wheat. In Triticeae, CBF is a multigene family with more than six members per genome and most of the CBF-cereal homologous sequences are clustered together on the long arm of chromosome 5. On the other hand, parallel genetic studies have identified several major genes and QTLs responsible for frost resistance or for components associated to frost restistance on each member of the 5th homoeologous chromosome of Triticeae. Soon after the discovery of the CBF transcription factors it was suggested that the CBF-cereal homologous genes might represent candidate genes for the loci controlling stress tolerance in cereals. Recent findings have demonstrated that the CBF locus cosegregates with one of the major QTLs for frost tolerance in barley and einkorn. This result represent one of the best successful examples of candidate gene approach for unraveling a complex phenotype such as the tolerance to abiotic stress.