Biology Reference
In-Depth Information
Fig. 4.4. The IR64 x Aday Sel NILs showed large differences in canopy temperature under severe drought and smaller
root and xylem vessel diameters. For a color version of this figure, please refer to the color plate.
soil is sampled to measure root length den-
sity by depth and root length within diameter
classes. If no differences in canopy tempera-
ture under drought are observed in root archi-
tecture between
shrinking columns of water in the soil, and per-
haps improved nutrient uptake.
The QTLs qDTY 2.2 and qDTY 4.1 were iden-
tified from an IR64 x Aday Sel population to
confer greater yield under drought (Swamy et al.
2013). The
QTL lines,
root anatomy and function (e.g., hydraulic con-
ductance) are then investigated. If the predomi-
nant differences between
+
QTL lines and
QTL lines from this population
also show an increased effect when drought
stress becomes more severe. Large differences
in canopy temperature and stomatal conductance
were observed between
+
QTL lines
under drought are NDVI and biomass, subse-
quent measurements focus on biomass partition-
ing and carbohydrate remobilization during grain
filling.
Thus far, physiological mechanisms behind
+
QTL and
QTL lines
under severe drought stress, but not under mod-
erate or mild drought stress, and no differences in
root architecture were observed between
+
QTL and
+
QTL
+
QTL lines from two separate populations have
been characterized at IRRI. Interestingly, the
traits identified are different from the most preva-
lent traits that have been used for selection for
drought tolerance; deep root growth and large-
diameter roots. The QTL qDTY 12.1 was identi-
fied from a Vandana x Way Rarem cross for
upland systems (Bernier et al. 2007), and it shows
an increasing effect with increasing severity of
drought stress. To compare
and
QTL lines (Swamy et al. 2013). A green-
house study was then conducted to examine root
hydraulic conductance and anatomy, from which
+
QTL lines stood out as having significantly
lower root hydraulic conductance and smaller
xylem and apical root diameter (Figure 4.4). It is
uncertain exactly how such altered root anatomy
contributes to yield under drought. More mea-
surements on these lines, including xylem vessel
cavitation and nighttime water flux from roots,
are necessary.
QTL
lines, a lysimeter study was conducted to mon-
itor water uptake by pot weight (Bernier et al.
2009). Lines with qDTY 12.1 showed a small but
significant (7%) increase in water uptake. This
QTL was subsequently characterized in rainout
shelter conditions, where
+
QTL and
Perspectives
Novel Marker-Assisted Breeding
Approaches
QTL lines showed
significantly lower canopy temperature under
drought, which was associated with a greater
proportion of fine (lateral) roots at shallow soil
depths. The increased proportion of lateral roots
may allow
+
The availability of large-effect QTLs affect-
ing grain yield under drought has opened the
way for the large-scale development of drought-
tolerant versions of susceptible high-yielding
varieties through marker-assisted breeding.
Novel approaches to marker-assisted breeding
QTL lines to perform better under
drought through better access to increasingly
+
Search WWH ::




Custom Search