Agriculture Reference
In-Depth Information
320
(a) Western Australia
(b) Eastern Australia
300
280
260
240
220
200
180
160
140
1950
1960
1970
1980
1990
2000
1960
1970
1980
1990
2000
Year of release
Fig. 11.13
Water-soluble carbohydrate content measured at anthesis for (a) Western Australian and (b) Eastern Australian
wheat cultivars released over 40 years and evaluated together in the fi eld.
reported studies have differed markedly in the
number of QTLs for WSC. For example, Yang
et al. (2007) reported a single QTL for WSC
measured 14 days after fl owering. This contrasted
with Rebetzke et al. (2008b), who identifi ed
between 8 and 16 QTLs across 3 populations for
WSC concentration sampled at the same devel-
opmental stage. Table 11.2 shows QTLs common
to two or more populations in Rebetzke et al.
(2008b). Physiologically these QTLs appeared
robust, as many of them collocated with QTLs
for WSC content, WSC per tiller, and plant
nitrogen content (Fig. 11.15).
Other opportunities exist for selection of stem
carbohydrates in wheat populations. The use of
NIR provides a robust assessment of WSC
without the need for expensive chemical analysis
(Fig. 11.5). Other workers (Blum 1998 and refer-
ences therein) have demonstrated the potential
for large-scale population screening of remobi-
lized WSC using chemical desiccants to remove
green leaf area.
400
350
300
250
200
150
1955 1960 1965 1970 1975 1980 1985 1990 1995
Year of release
Fig. 11.14
Water-soluble carbohydrate content measured
at anthesis for CIMMYT wheat cultivars released over 40
years and evaluated together in the fi eld.
anthesis and fi nal biomass. Days to heading, plant
height, and nitrogen contents were similar for
low- and high-selected WSC content lines
(Rebetzke et al., 2008b). Therefore, it is important
that, when selecting, breeders distinguish between
genotypic differences in WSC concentration and
WSC content.
Genetic studies have characterized WSC
concentration with low to moderate genotype
Tiller production
Current wheat cultivars initiate more tillers than
they can sustain. Cool, moist conditions and high
nutrient levels soon after emergence are very
favorable for tiller initiation. Typically each plant
produces between 5 and 20 tillers at stem elonga-
×
environment interaction, which may lead to
higher heritability and expected selection response
(Rebetzke et al., 2008b). Extension to WSC
content showed lower heritability, owing to larger
errors when sampling anthesis biomass. The few
