Agriculture Reference
In-Depth Information
7* + 8, which has been assigned the allele designa-
tion
Glu-B1u
, indicated for example in the culti-
var Sunco. Normal 7 + 8 is rare, and there is
insuffi cient rheological data for it to be included
in Table 21.3.
There is much more (about threefold) of the
LMW subunits in glutenin compared with
the HMW subunits, but the contribution of the
HMW subunits to dough resistance is more sig-
nifi cant than would be expected by their smaller
proportion in the glutenin fraction. The LMW
subunits do contribute to dough strength, but
their great importance relates to extensibility
(Table 21.2). Therefore, selection against null
alleles at
Glu-1
and
Glu-3
(e.g.,
Glu-A1c
and
Glu-
A3e
) has the important effect of increasing dough
strength and extensibility (Table 21.4). Null
alleles are thus seen as undesirable. At the other
extreme, a few of the
Glu-1
alleles (e.g.,
Glu-
B1al
) are overexpressed (subunit
7
in Table 21.3),
so that the resulting subunits appear in the endo-
sperm in more than the normal amounts for other
subunits; as a result, the presence of these alleles
causes major changes (increases) in the genetic
potential for both dough strength and extensibil-
ity. Overexpression of glutenin subunits has also
been observed in transgenic wheat (Rooke et al.,
1999).
The “
Glu-1
” score system of Payne et al. (1987)
was designed to indicate the individual contribu-
tions of specifi c HMW subunits (and thus the
associated genes) to baking quality. Despite the
age of this scheme, and despite the lack of inclu-
sion of the LMW subunits and overexpressed
genes, the
Glu-1
score is an effective tool for
breeders wanting to target the genetic potential of
progeny for specifi c dough-quality attributes.
Furthermore, predictions based on gluten alleles
offer advantages at all stages of the “grain chain.”
More recently, fuller systems have been devel-
oped taking into account the results of subsequent
research, such as is listed in Table 21.3. Given the
complex nature of processing specifi cations (Table
21.1), it is appropriate to provide recommenda-
tions (Table 21.5) for the ideal combinations of
glutenin alleles that would be expected to provide
dough quality attributes appropriate to various
processing needs.
A valuable application of this type of informa-
tion is the selection of parent lines with sets of
alleles suited to the targeted quality outcome. To
assist in this respect, glutenin subunits have been
catalogued for large numbers of cultivars and
lines worldwide; they are available in McIntosh
et al. (2003) or at the web site of AACC Interna-
tional http://www.aaccnet.org/grainbin/gluten_
gliadin.asp.
Table 21.4
Dough-strength rankings, from highest (top) to
lowest (bottom), for LMW glutenin subunits (
Glu-3
).
Glu-A3
Glu-B3
Glu-D3
d
b
;
d
;
g
;
m
d
;
f
b
h
e
c
a
a
;
c
;
b
f
c
a
e
Table 21.5
Best quality alleles for various wheat products.
Genes
Pan Bread
Flat Bread
Yellow Alkaline Noodles
White Salted Noodles
Cookies and Cakes
Glu-A1
a
,
b
a
,
b
a
,
b
a
,
b
c
Glu-B1
c
,
f
,
i
,
u
,
al
c
,
f
,
i
,
u
c
,
f
,
i
,
u
,
al
c
,
f
,
i
,
u
d
,
e
Glu-D1
d
a
a
,
d
a
a
,
c
Glu-A3
b
,
d
b
,
c
b
,
d
b
,
c
b
Glu-B3
b
,
g
b
,
d
,
h
b
,
g
b
,
d
,
h
b
,
d
Glu-D3
a
,
b
a
,
b
,
c
a
,
b
a
,
b
,
c
a
,
b
,
c
Pina-D1
a
b
a
a
a
Pinb-D1
b
a
b
a
a
Wx-B1
b
a
,
b
a
b
a
,
b
Source:
Adapted from Cornish (2007).
