Agriculture Reference
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are activated. These GPC-regulated genes, particularly those up-regulated during
senescence, provide valuable entry points to dissect the early stages of monocarpic
senescence and nutrient remobilization in wheat.
Another main miner bioavailability limiting factor is the presence of phytic acid
(PA). PA is stored in the aleurone layer and hampers the intestinal absorption of
mineral cations by making insouluble complexes (Cheryan,
1980
). Phytase activity
of the flour strongly reduces the PA breakdown. Therefore, the mineral bio-avail-
ability depends on, both, mineral and phytase concentrations and these should be
taken into account in wheat improvement for biofortification. Recently, Ram et al.
(
2011
) indicated the presence of higher genetic variability of phytase in synthetic
hexaploids as compared to Indian cultivars. There is a greater scope for manipu-
lating phytase levels as compared to phytate in wheat breeding, due to the larger
genetic effects and greater genetic variability of the phytase in wheat. Thus, D-ge-
nome synthetics hold significance to be used as source for increasing phytase levels.
The release of cultivars with high mineral concentrations complemented with high
intrinsic phytasic activity could greatly improve the nutritional value of bread, pro-
vided that less refined flour is utilized to preserve the source of the minerals. CIM-
MYT nearly a decade ago screened some wheat progenitor resources and identified
accessions of
T. dicoccon
with elevated levels of iron and zinc. On these tetraploids,
synthetic hexaploids were developed by the wide crossing unit and produced stocks
(
T. dicoccon/Ae. tauschii)
for wheat breeding program. A nursery set has been de-
ployed in India and Pakistan from which promise has been observed but impacting
findings are still awaited.
QTLS for Grain Quality Traits
Understanding the genetic architecture underlying quality traits is essential to iso-
late and characterize the desirable genes. Extensive QTL mapping studies have
been performed to study the genetic control of quality traits. The recent trend shifted
to association mapping is the further extension to bi-parental mapping to study the
QTLs with accuracy and precision (Mascri et al. 2012). Earlier, Campbell et al.
(1999,
2001)
identified QTL for kernel, milling, and baking traits. QTL for kernel
traits are located on chromosomes 1A, 2B, 2D, 3B, 7A, and 7B. Earlier to this,
Parker et al. (
1998
) identified two major loci for flour color on chromosomes 3A
and 7A, using RFLP marker in 150 RILs. In quantitative terms, the most important
trait is flour yield and several QTLs have been identified for this trait on chromo-
somes 4A, 4D, 5D (Nelson et al.
2006
), 5D (Campbell et al.
2001
) and 7D (McCart-
ney et al.
2006
). Recently, Carter et al. (
2012
) identified two QTLs on chromosome
7B explaining the 17 and 19 % variability in 188 RILs population. Similarly, flour
and grain protein identified as a key quality trait largely influencing the quality at-
tributes of dough had several QTLs identified in RILs (Nelson et al.
2006
; Carter
et al.
2012
) and double haploid (McCartney et al.
2006
; Huang et al.
2006
) mapping
populations. Two QTLs on chromosomes 2D and 4D explained about 30 % of the
phenotypic variability and were also validated by other researchers.
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