Freezing Tolerance in the Triticeae - Translational Genomics for Crop Breeding: Abiotic Stress, Yield and Quality - page 117

addition, the frost-tolerant genotypes can also
acclimate faster in comparison to the frost-
sensitive ones (Fowler 2008). This behavior
could be further studied, since it would give an
adaptive mechanism to plants subject to frost in
reproductive (sensitive) phases or to plants sub-
ject to fast and dramatic fluctuations of tempera-
ture. Lastly, research on sensing mechanisms, as
on speed of acclimation cascade, could be cou-
pled with integrative biology research in order
to achieve a better understanding of FR-1 and
FR-2 loci interaction. It would then be impor-
tant to know how different molecular networks
interact in response to various abiotic stresses.
Epigenetic studies until now have revealed how
the methylation patterns of histones at VRN-1
change in response to vernalization, thus medi-
ating its environmentally regulated expression
(Oliver et al. 2009), but, for example, no epi-
genetic studies have been done on CBF reg-
ulation. If we take an optimistic view, for
Triticeae, modern high-throughput screening
methods could soon enable us to carry out
genome-based selection of genotypes possessing
desired genomic structures. The new approaches
should, one would hope, lead to the development
of new cultivars with physiologically tailored
characteristics and with an improved versatility
against abiotic stresses, underlying the plant's
ability to cope with rapidly changing environ-
ments.

Conclusions and Perspectives

Global climate change will demand increas-
ing versatility of crops to acclimate to multi-
ple and dramatically fluctuating abiotic stress
factors (Fedoroff et al. 2010). As underlined
above, selection for an enhanced frost tolerance
will remain an important aim of cereal breeding
programs in temperate climate zones, together
with tolerance to drought, salt, flooding, and
improved nutrient efficiencies. Moreover, selec-
tion for multiple stress tolerances should be
coupled with fine tuning of the growth cycle,
by manipulating VRN , PPD , and EPS ( Earli-
ness per se ) genes, as suggested by Francia and
colleagues (2011). Since the late 1970s, when
Olien (1979) and then Levitt (1980) described
the events leading to frost damage in plants, an
impressive amount of experimental evidence has
accumulated for genetic and molecular mech-
anisms that allow plants to tolerate freezing
temperatures. Many pieces of the puzzle are in
place, as described in this chapter, and together
will allow wheat and barley improvement to be
driven by means of simple DNA-based technolo-
gies. Some as yet unresolved issues could be
addressed in the near future. First of all, little
is known about the molecular mechanisms of
low temperature sensing by the Triticeae cells.
A few regulatory steps above the CBF/DREB
genes are known in the model plant Arabidopsis,
with a role for calcium and calmodulin signaling
(Doherty et al. 2009), but the information is far
from complete. Knowledge of this process could
perhaps help to improve the speed of the acclima-
tion cascade. For example, it is already known
that frost tolerant wheat and barley genotypes
are able to induce the cold acclimation machin-
ery at higher temperatures than the susceptible
ones. This, firstly observed in barley (Crosatti
et al. 1995), spawned the hypothesis of thresh-
old induction temperatures (Galiba et al. 2009).
According to the hypothesis, frost-tolerant geno-
types start decreasing their LT 50 values and
accumulating COR transcripts at higher growth
temperatures than the frost-sensitive ones. In

Acknowledgements

This research was supported by the Hungarian
Scientific Research Fund (CNK80781, OTKA
K83642) and by by the National Develop-
ment Agency grant 1021 T AMOP-4.2.2/B-10/
1-20100025 Doctoral School of Molecular- and
Nanotechnologies, 1022 Faculty of Information
Technology, University of Pannonia.
Research was supported by Fondazione Cassa
di Risparmio di Modena, Progetto di Ricerca
Internazionale “FROSTMAP - Physical map-
ping of the barley Frost resistance-H2 (Fr-H2)
locus”. Funding from “GENOMORE” project