Freezing Tolerance in the Triticeae - Translational Genomics for Crop Breeding: Abiotic Stress, Yield and Quality - page 111

Rinalducci et al. 2011; Vıtamvas et al. 2012).
In leaves of cold-treated wheat the concentration
of those proteins involved in defense (ascorbate
recycling) and protein processing increased, and
the concentration of those related to the Krebs
cycle and photosynthesis decreased (Rinalducci
et al. 2011).
A comparison of two wheat genotypes with
different freezing tolerance and vernalization
requirement showed a close association between
the vernalization fulfillment and the start of
a decline in the protein accumulation during
growth at low temperature (Sarhadi et al. 2010).
The authors also observed that the concentra-
tion of proteins related to defense, photosynthe-
sis and metabolism was affected by cold. Com-
parison of chromosome 5A substitution lines
having this chromosome from genotypes with
different frost tolerance to each other revealed
the effects of chromosome 5A and 5B on pro-
tein accumulation during long-term cold accli-
mation (Vitamvas et al. 2012). Similarly to the
transcriptome level (Herman et al. 2006), at the
proteome level a decrease in the amount of sev-
eral photosynthetic proteins indicated the impair-
ment of the photosynthetic processes (Vitamvas
et al. 2012). A time lag between a down-
regulation of cold-inducible transcripts and cold-
inducible proteins was proposed in vernalized
winter wheat plants, especially when COR/LEA
proteins were investigated. A down-regulation
of cold-inducible proteins in vernalized, but
still cold-treated, winter wheat plants imme-
diately after the vegetative/reproductive transi-
tion would have fatal effects on their survival
(Sarhadi et al. 2010, Vıtamvas et al. 2012). The
time lag between the down-regulation of tran-
scripts and proteins would ensure the survival
of the plants at low temperature after this tran-
sition for a certain period, due to the prolonged
existence of the protective proteins. The impor-
tance of several COR/LEA proteins in the pro-
tection of cell content during frost may be indi-
cated by the fact that their relative abundance
is correlated with the level of freezing toler-
ance of cold-treated spring and winter wheat

genotypes (Houde et al. 1992). Transcriptomic
and proteomic studies with wheat and barley
indicate that cold acclimation induces freezing
tolerance-dependent changes in the level of sev-
eral mRNAs and proteins. Future comparative
investigations are necessary in order to clarify
which similarities and differences exist in the
cold-induced changes in the transcriptome and
proteome between barley and wheat.

GeneticResources

The Middle East region known as the Fertile
Crescent is considered the center of origin for
cultivated Triticeae, based on the presence in this
area of their wild progenitors and the archeolog-
ical evidence (Zohary and Hopf 1993). Climatic
conditions of this region are reflected in the win-
ter growth habit characterizing the majority of
wild progenitors of the tribe (Kosova et al. 2008).
Together with a quantitative long-day response,
winter growth habit is thus considered ances-
tral for the cultivated wheats and barley. After
agriculture spread outside the Fertile Crescent,
arriving at the Balkans around 6000 B.C., and
to Europe over the following 2,000-3,000 years
(Lister et al. 2009), novel adaptive traits suited
to the new environments were selected. One of
them was the spring growth habit that enabled
expansion of cereal cultivation at higher lati-
tudes without damage by cold winters (Cock-
ram et al. 2009) and taking advantage of long
growing seasons due to reduced photoperiod
response (Peng et al. 2011). This brought into
existence two more groups of barley and wheat,
apart from winter types, divided according to
the vernalization requirement: spring types and
rarer facultative types. Satisfaction of vernaliza-
tion is necessary for winter Triticeae to flower,
although not strictly so; a strong delay in flower-
ing occurs under prolonged long-day conditions,
even without any period of cold, while the spring
types have no vernalization requirement. There
is more than one description for the facultative
type; according to the International Union for the
Protection of New Varieties of Plants (UPOV)