Translational Genomics for Crop Breeding: Abiotic Stress Tolerance, Yield, and Quality, Introduction - Translational Genomics for Crop Breeding: Abiotic Stress, Yield and Quality - page 3

Enhancing Tolerance to Abiotic
Stresses in Rice

However, during the past decade the availability
of large-scale genomic resources and genome
sequences have enabled the adoption of various
GAB approaches in rice (see Collard et al. 2008).
These efforts are summarized in Chapter 4 by
Kumar and colleagues.
Sixteen essential elements are required for
rice during the crop cycle. The major nutrients
such as nitrogen (N), phosphorus (P), and potas-
sium (K) are largely supplied as chemical fer-
tilizers. The excess application of P, owing to
its insoluble nature, leads to deficiencies of cop-
per (Cu), iron (Fe), manganese (Mn), and zinc
(Zn). Additionally, erosion of P-enriched soils
enhances eutrophication in fresh water (Wolf
1996). Most of the rain-fed rice grown in Asia
and Africa is cultivated on problematic soils,
especially when P becomes unavailable to the
crop as it adheres to soil particles. Hence, in this
context, development of crops with enhanced
efficiency of P utilization and production of
higher biomass is essential. Chapter 5 by Heuer
and colleagues essentially discusses the issues
related to P deficiency in rice production. Fur-
ther, the authors also highlight the need for the
adoption of molecular breeding approaches and
summarize the molecular breeding efforts for
enhancing P utilization efficiency in rice.

Submergence stress affects more than 15 Mha
in lowland rice-growing areas of South and
Southeast Asia. Chapter 2 provides insights
into the ongoing efforts at the International
Rice Research Institute (IRRI), Manila, Philip-
pines, to improve submergence tolerance in rice.
Following the identification of Sub1 ( Submer-
gence1 ) locus and three ethylene responsive fac-
tors (ERFs) in rice, Septiningsih and colleagues
report the development of eight Sub1 varieties by
the IRRI, six of which are already widely grown
in several countries.
More than 444 Mha of global rice-growing
area is affected by soil salinization (FAO, 2010).
Soil salinization is a major problem in coastal
areas of the regions where rice-based farming
predominates. Reportedly rice yields are reduced
by up to 50% when grown under moderate
(6 dS/m) salinity levels (Ren et al. 2005). The
losses due to soil salinization can be overcome
by soil reclamation or by improving salinity tol-
erance in the crops. Efforts toward understanding
the genetic basis of the trait for crop improve-
ment has revealed that several genes are inde-
pendently involved in salinity tolerance at differ-
ent stages of crop cycles. In Chapter 3, Platten
and colleagues provide an overview of genomics
applications in enhancing salt tolerance in rice.
Drought is the major limiting factor to crop
production, and cereals especially experience
various kinds of drought stresses, depending on
the timing and intensity of the water stress rel-
ative to the reproductive stage of the crop. In
the case of rice, in Asia about 34 Mha of rain-fed
lowland rice and 8 Mha of upland rice (Huke and
Huke 1997) are frequently subjected to drought
stress. Progress in developing high-yielding,
drought-tolerant rice cultivars by conventional
breeding has been slow, largely because of dif-
ficulties in precisely defining the target environ-
ment, complex interactions of drought tolerance
with environments and management practices,
and lack of appropriate screening methodology.

Enhancing Tolerance to Abiotic
Stresses in Wheat and Barley

Freezing/cold tolerance in crop plants is most
important in the context of global climate
change. Freezing tolerance is important in tem-
perate cereals such as wheat ( Triticum spp.), bar-
ley ( Hordeum vulgare ), and rye ( Secale cereale ).
Long exposures of winter wheat and barley vari-
eties to non-freezing cold temperatures (Dhillon
et al. 2010) will accelerate flowering time (ver-
nalization) and improve freezing tolerance (cold
acclimation). In the case of wheat, Kobayashi
et al. (2005) reported that Vrn-Fr1 controls
both frost tolerance and vernalization. Chap-
ter 6, by Gabor and colleagues, reports on the
developmental plasticity of these Triticeae crops