Key molecular and metabolic processes used for genetic engineering to improve freezing tolerance in cereals.

It has been estimated recently that cereals are harvested on 700 million hectares (Mha) worldwide (Dunwell, 2014), and also that, due to low temperature damage, worldwide losses in crop production amount to about US$2 billion each year (Sanghera et al., 2011). In spite of the urgent need for more coldor frost-tolerant cereal varieties, classical breeding programmes have shown limited progress in improving freezing tolerance (Thomashow, 1999). This lack of success is due mainly to the fact that the physiological process, i.e. the cold acclimation that leads to the development of freezing tolerance, is quite a complex quantitative trait. However, the deeper insight provided by different ‘omics’ technologies has made possible knowledge-based engineering of more stress-resistant plants; while the recent developments in cereal transformation methodology offer the technology to realize these aims. Since many recently published book chapters and reviews summarize our current knowledge on plant abiotic stress tolerance, this chapter focuses particularly on freezing tolerance, especially in cereals.