'Plant Breeding: Sustaining the Future' Abstracts of the XVIth EUCARPIA Congress, Edinburgh, Scotland, 10-14 September 2001 GENES FOR ABIOTIC STRESSES RESISTANCE IN SMALL GRAIN CEREALS L. CATTIVELLI, C. CROSATTI, M. GROSSI, F. RIZZA, C. MARÈ, A.M. MASTRANGELO, E. FRANCIA, E. MAZZUCOTELLI, C. GOVONI, A.M. STANCA Experimental Institute for Cereal Research Section of Fiorenzuola d’Arda – Via S.Protaso 302 - I-29017 Fiorenzuola d’Arda (PC), Italy

To achieve high yielding capacity and yield stability over-winter crops have to survive and grow during the cold season. A fundamental component of the “winter survival capacity” is represented by the freezing tolerance, which is based on an inducible process, known as hardening or cold acclimation, that occurs when plants are exposed to low non-freezing temperatures. Frost resistant plant cells show variations in hormones and osmolytes content as well as in the properties of the membranes and of the photosynthetic apparatus. The molecular dissection of cold hardening revealed a complex situation, where the co-ordinated expression of a series of cold-regulated genes (cor genes) is associated with increased frost resistance. Several cor genes are also involved in the plant response to drought, while other cor genes are only expressed at low temperature. The expression of low temperature specific cor genes is impaired in plants carrying albina or xantha mutations suggesting that a chloroplast factor is required for cold signal perception and transduction. Using specific antibody it has been demonstrated that two chloroplast dependent cor genes (cor14b and tmc-ap3) encode for proteins imported into the chloroplast. In barley the expression of cor14b is promoted when temperature is below 10°C. The corresponding protein is then localised into the stroma fraction of the plastid. Low accumulation of COR14b is induced by cold treatment in etiolated plants, although cor14b expression and protein accumulation can be fully restored after a short light pulse. The amount of COR14b accumulated into the chloroplast is also dependent from the redox state of the plastoquinone suggesting a relation between the status of the electron transport chain and the molecular response to cold. tmc-ap3 is a cor gene weakly expressed at 20°C, nevertheless tmc-ap3 mRNA accumulation increase as the temperature decrease. The cor protein TMC-AP3 is located onto the outer envelope and it shares a high homology with a putative amino acid selective channel protein.  Genetic analysis have shown that the amount of the chloroplast localised cor proteins accumulated during hardening is positively correlated with the level of frost tolerance in barley and wheat. Frost resistant cultivar accumulated COR14b and TMC-AP3 more rapidly and at higher level than frost susceptible ones. Studies made with wheat chromosome substitution lines showed that the expression of cor14b is controlled by two loci located on the chromosome 5A near to the frost resistance locus Fr1, demonstrating a linkage between the induction of cor14b and frost resistance. The genetic relationship between the main locus involved in winter survival and the expression of several cor genes controlled through a chloroplast mediated signal transduction pathway, suggest a possible role of these genes in plant adaptation to cold environments.