Effect of barley yellow dwarf virus on the yield components
of spring wheats.
S. Haber and R.I.H McKenzie.
In western Canada, the development of wheat germplasm
that performs well under BYDV disease pressure has received less
attention than that for oat or barley until recently. This is
partly because wheat has been considered to be less at risk, and
partly because good sources of resistance or tolerance in acceptable
genetic backgrounds were not available until fairly recently.
Beginning in 1988, field trials at Glenlea near Winnipeg
have clearly shown that representative western Canadian spring
wheat cultivars are vulnerable to losses of at least 50 % from
BYDV (Tekauz et al. 1992). Field trials at Glenlea using artificially
applied aphid inoculum have identified lines derived from CIMMYT
(Mexico) wheat germplasm that performed well under high BYDV disease
pressure. In 1995 and 1996, the most promising of these lines
were rigorously evaluated under BYDV disease pressure, and their
performance was compared with that of current representative western
Canadian wheat cultivars.
The losses observed in inoculated plots compared
with their insecticide-protected split-plot counterparts
can be properly attributed to the effects of BYDV infection for
both years by comparing the performance of susceptible Manley
barley with its resistant close relative, TR241 (Table 1). Katepwa,
a CWRS cultivar, suffered the greatest proportional yield losses
in both years. The two CIMMYT-derived lines, 93w1296 (SERI/THB"S"),
and 93w1307 (an advanced-generation reselection of 93w1296),
experienced much smaller losses. AC Foremost, derived from CIMMYT
parents, is a CPS cultivar, and was intermediate in performance
Table 1. Effect of barley yellow dwarf virus on yield (per 50 cm harvested row).
|Line tested||Status||1995 yield (g)||1995 ratio (BYDV/protected)||1996 yield (g)||1996 ratio (BYDV/protected)|
|Manley barley (susceptible check)||protected||112.86||-||109.05||-|
|TR241 barley (+Yd2)||protected||116.78||-||158.59||-|
|AC Foremost wheat||protected||96.76||-||71.82||-|
|93w1296 wheat SERI / THB S||protected||131.66||-||126.24||-|
|93w1307 wheat SERI / THB S||protected||127.92||-||135.07||-|
Table 2. Effect of barley yellow dwarf virus on 1,000-kernel weight (per 50 cm harvested row).
|Line tested||Status||1995 (g)||1995 ratio (BYDV/protected)||1996 (g)||1996 ratio (BYDV/protected)|
|Manley barley (susceptible check)||protected||36.81||-||38.12||-|
|TR241 barley (+Yd2)||protected||38.67||-||39.52||-|
|AC Foremost wheat||protected||24.37||-||19.08||-|
|93w1296 wheat SERI / THB S||protected||27.74||-||24.35||-|
|93w1307 wheat SERI / THB S||protected||27.00||-||24.77||-|
The differences between 1995 and 1996 for the effect
of BYDV on yield likely arose from the interaction of BYDV with
environmental factors (Haber 1995). In 1995, the trial was seeded
1 June, and inoculations were made in mid-June. The last
2 weeks in June experienced high temperatures and associated drought
stress. By contrast, the 1996 trial was not seeded until mid-June,
but rainfall was adequate and timely during the growing season
and there were no temperature extremes. All lines tested experienced
smaller yield losses under BYDV disease pressure in 1996 than
in 1995. The CIMMYT-derived and closely related lines 93w1296
and 93w1307 performed similarly in the milder conditions prevailing
in 1996, but 93w1296 performed significantly better in 1995.
Among the components of yield loss (Tekauz et al.
1992), reduction in seed size (as reflected in 1,000-kernel
weight) is of the greatest concern, because it affects quality
as well as yield. The trials revealed clear differences among
the lines tested with respect to this parameter. Seed size of
hand-harvested grain from Katepwa plots under BYDV pressure
was reduced to such an extent in the 1995 trial that the seed
would probably be usable only for feed. AC Foremost, 93w1296,
and 93w1307 experienced only small effects (Table 2). In the
1996 trial, those lines with the greatest reduction in seed size
in 1995 had smaller reductions, whereas the effects attributable
to BYDV were similar for AC Foremost, 93w1296, and 93w1307 (Table
2). However, AC Foremost produced small seed in both protected
and infected plots in 1996, because its vernalization response
was a factor when sown late.
Haber S. 1995. Barley Yellow Dwarf Virus: Cross-protection
and interactions with other pathogens and with abiotic factors.
In: Barley Yellow Dwarf, 40 Years of Progress (D'Arcy
CJ and Burnett PA eds). APS Press, St. Paul. pp. 122-159.
Tekauz A, Haber S, and Gilbert J. 1992. Effect
of barley yellow dwarf virus and Septoria spp. in single
or tandem infections on yield components of spring wheat. Can
J Pl Path 14:248 (abstract).
Durum wheat quality: comparison of chemical and rheological
screening tests with sensory analysis.
M.I.P. Kovacs, L.M. Poste, G.S. Butler, S.M. Woods, D. Leisle, J.S. Noll, and G. Dahlke.
Various chemical and physical screening tests to
predict the cooking quality of pasta in wheats from a durum wheat
breeding program were evaluated using sensory methods. Twelve
durum wheat varieties were field-grown for 3 consecutive years,
milled into semolina, and then processed into spaghetti using
a low temperature drying scheme. Correlations between protein
and sensory scores were not consistent among the 3 years, and
protein content did not correlate with any of the tests used to
predict pasta cooking quality. Cooked pasta disc viscoelasticity
measurements are reliable predictors of sensory quality. Sedimentation
values and cooked gluten viscoelasticity were significantly correlated
with chewiness in 2 of the 3 years. Mixing total energy and mixing
peak height values obtained using a mixograph were the best predictors
for chewiness and firmness. None of the tests correlated with
adhesiveness to teeth, which suggests that it is an unrelated
parameter. The mixograph test is the most useful test to predict
the use quality of durum wheat in a breeding program, because
it is simple, requires relatively small sample size, and gives
results that are highly correlated with sensory data.
The interaction between flour milling extractions and wheat
noodle browning in three different genetic sources of kernel o-diphenol
M.I.P. Kovacs, N.K. Howes, R.I.H. McKenzie, and R. DePauw.
Dough browning in fresh, salted, or alkali noodles
is attributed to polyphenol oxidase (PPO) enzymes (tyrosinase,
o-diphenol oxidase) present in the bran layer of the
wheat kernel. At least three distinct genetic sources of PPO
activity are present in hexaploid wheat, a high source including
the CPS wheats Genesis and Biggar, a low source present in the
CPS breeding lines HY367 and HY398, and a zero PPO source, 332-B,
derived from the synthetic hexaploid RL5710. The PPO levels in
whole meal from the low and zero source are 14-20
% and < 1% of the level of Genesis and Biggar. Flour extraction
rates of 85 % for HY398 and 332-B gave a similar level of
PPO and increase in dough sheet browning after 4 h or 24 h as
a 60 % extraction of Genesis and a 70 % extraction of Biggar.
PPO measurements with a 1-gram flour sample confirmed that this
was a reliable, sensitive, and fast measurement of dough browning
potential. The low and zero PPO sources should enable dramatically
higher flour-extraction rates in cultivars containing these genes.
Quality characteristics of durum wheat lines deriving high
protein from a Triticum dicoccoides (6B) substitution line.
M.I.P. Kovacs, N.K. Howes, J.M. Clarke, and D. Leisle.
One of the objectives in the Canadian durum wheat
breeding programs has been the selection of lines with higher
protein content. The Langdon-T.
dicoccoides (6B) substitution, a source
of high protein, has been introgressed into two high-yielding,
but lower protein Canadian durum wheats. The resulting lines,
with protein contents similar to registered cultivars, were evaluated
for protein quality. The introgression had no detrimental effect
upon pasta cooking quality. Thus, the T. dicoccoides-6B
chromosome substitution will be a valuable route for increasing
protein level in the durum breeding program.
A 2-gram flour test for extensibility and resistance to
extension. M.I.P. Kovacs, N.K. Howes, J.M. Clarke, and D. Leisle.
M.E. Ingelin and O.M. Lukow.
Dough properties such as extension and resistance
to extension are important parameters in measuring flour quality
and predicting end-product suitability. The AACC standard
method uses a 300 g farinograph bowl to mix the doughs to be tested.
Aside from requiring relatively large flour samples, this method
may be inappropriate for some flours. Doughs used for testing
extension and resistance to extension often contain 2 % added
salt. Flours milled from CWESRS wheats with this added salt have
farinograph development times exceeding 30 min. When these doughs
are tested on the Brabender extensograph, they exceed the instrument's
maximum resistance and extension limits. When the 2-gram mixograph
is used to mix the same flours with the same salt addition, mixing
times are reduced from over 30 min to 7-8
min. The doughs are loaded into the Kieffer rig supplied by Stable
Micro Systems after mixing in the mixograph. A single, 2-gram
mixograph dough has sufficient mass for three test pieces. The
dough pieces are rested at 30C
for 45 min, then tested using a TA.XT2 Texture Analyser. After
some initial adjustments, dough extensibility and maximum resistance
can be measured without exceeding the maximum limits of the texture
analyser. Comparisons in peak force and area between the 300-gram
and 2-gram test have R2s of 0.74 and 0.77, respectively.
The frozen dough performance of diverse wheat cultivars.
O.M. Lukow, C.E. Perron, X. Chen, W. Bushuk, and T.F. Townley-Smith.
Several studies were done that examined the performance
of 16 wheat flour samples in a frozen dough system. Cultivars
were grown at five locations in western Canada over a 3-year period
and represented several wheat classes, including the CWRS, CWESRS,
and DNS classes, and some French and Italian varieties. Factors
such as the relative frozen dough baking quality, tolerance to
the detrimental effects of frozen storage, and the frozen dough
blending performance of the cultivars were considered. In straight
frozen dough baking, the cultivars Roblin, Katepwa, Neepawa, Laura,
Prinqual, and Grandin had the best loaf volumes. Doughs made
with Glenlea, Wildcat, Bluesky, Pembina, and Florence-Aurore
wheats (stronger dough properties according to mixograph and farinograph)
had lower loaf volumes, but ranked higher in terms of crumb structure
and loaf appearance. Frozen storage was not detrimental to loaf
volume when dough strengtheners were included in the formulation.
However, a reduction in crumb and loaf appearance scores was
evident after the 16-week storage period, the magnitude of this
effect being cultivar dependent. The extra-strong varieties
Bluesky, Wildcat, and Glenlea, and Manital, Grandin, Florence-Aurore,
Roblin, and Darius, exhibited the least loaf quality deterioration.
These cultivars also tended to produce breads with the best overall
loaf quality when blended with a weaker flour at a level of 50
%. The relationship between frozen dough baking performance and
protein content, protein quality, and dough rheological properties
has been examined.
The contribution of protein composition to dough strength
and baking quality using double haploid lines.
O.M. Lukow, C.E.Perron, and T.F. Townley-Smith.
Double haploid lines from the cross between semidwarf
Glenlea and AC Domain have been produced to study the genetic
basis of dough strength and baking quality differences between
the parents. Glenlea wheat has extra-strong mixing characteristics,
which appear to be due to the presence of HMW-glutenin subunits
7+8; overproduction of subunit 7; and LMW-glutenin subunits
50, 8, and 10. Stronger dough properties have been associated
with improved baking quality for many wheat varieties. However,
in standard baking tests, the extra-strong mixing properties
may exert a negative effect on loaf volume potential. Conversely,
it is these rheological properties that make Glenlea-type
wheat ideal for use as a blending wheat and have led to its recent
popularity in the frozen dough industry. The effect of specific
protein banding patterns on nonfrozen baking performance is being
evaluated. Two procedures have been used, the AACC straight dough
method using a long bulk fermentation period and a no-time
dough procedure, the Canadian Short Process. The DH lines also
are being tested in both blending and frozen dough tests. As
a result, the wheat protein characteristics most suitable for
nonfrozen and frozen dough production and for blending with weaker
wheats will be identified.
Wheat leaf rust in Canada in 1996.
Leaf rust incidence and
severity. Leaf rust of wheat, caused by P. recondita
f.sp. tritici was first observed in winter wheat at Carman,
Manitoba, on 26 June. Cold spring weather delayed planting in
Manitoba in 1996 and also delayed the initial onset and subsequent
spread of leaf rust. The cool spring weather also delayed wheat
planting and rust development in the north central region of the
U.S. Leaf rust migrates to Manitoba from the U.S. on an annual
basis. Drought conditions in Kansas also may have reduced the
amount of leaf rust that arrived in Manitoba in 1996. Throughout
Manitoba and Saskatchewan, leaf rust infection levels were light,
due to the combination of weather conditions and increased planting
of highly leaf rust resistant bread wheat cultivars such as AC
Domain and AC Cora. However, CPS cultivars such as AC Foremost
and AC Karma had high levels of leaf rust infection. The leaf
rust resistance in current CPS cultivars may not be sufficient
Physiologic specialization. Collections
of leaf rust-infected flag leaves were made from wheat cultivars
and lines planted in rust nurseries grown throughout Canada and
also from wheat plants in farmer's
fields. The collections were increased on seedlings of the susceptible
cultivar Little Club, and 2-3
single pustules were obtained from each collection 3 weeks after
inoculation. The single pustules were inoculated on the primary
leaves of 16 Thatcher NILs for seedling leaf rust resistance genes.
The differential sets were grown at 15-20C
in a fluorescently-lit greenhouse. The infection types for the
single-pustule isolates on the differential lines were evaluated
12 days after inoculation. Infection types were rated on a scale
0 = no visible infection; 1 = small necrotic areas with limited
sporulation; 2 = small pustules with pronounced chlorosis; 3 =
medium sized pustules with little chlorosis; and 4 = large pustules
with little chlorosis. Infection types 0-2+
were considered as avirulent, and infection types 3-4
were considered virulent. Each single pustule isolate was rated
as avirulent or virulent on each differential line. The three
letter Prt nomenclature system (Long and Kolmer 1989) was
used to describe the virulence phenotype of each single pustule
isolate. A fourth letter was added to describe the avirulence/virulence
of the isolates to resistance genes LrB, Lr10, Lr14a,
Table 3. Virulence frequencies (%) to isogenic `Thatcher' wheat lines with single genes for leaf rust resistance in Puccinia recondita f. sp. tritici in Canada, in 1996.
|Resistance gene||Quebec||Ontario||Manitoba / Saskatchewan||Alberta|
|Total # of isolates||25||28||204||18|
Leaf rust races with virulence to Lr17 and
LrB increased to over 40 % in 1996 in Manitoba and Saskatchewan
from 1 % in 1995. Winter wheats in the southern plains of the
United States with these resistance genes most likely selected
races with virulence to Lr17 and LrB. The most
common race in Manitoba and Saskatchewan - MBDS - has
virulence to both of these genes. Virulence to Lr16 in
1996 did not increase over levels of 1995, remaining less than
10 % of isolates in Manitoba and Saskatchewan. Many HRSWs in
Manitoba and Saskatchewan have Lr16. Race SBDD was found
in collections from Quebec. Over the last 20 years, this race
had been collected only from wild goatgrass in the southern plains
of the United States. The predominant races collected from the
winter wheats in Ontario remained relatively unchanged from previous
years. Isolates of race MBDS in Quebec were collected from spring
wheats. The other predominant races in Quebec collected from
winter wheats remained relatively unchanged from previous years
(see Tables 3 and 4).
Table 4. Frequency (%) of predominant (> 5 %) virulence phenotypes of Puccinia recondita f.sp. tritici in Canada, in 1996.
|Race||Virulences||Quebec||Ontario||Manitoba / Saskatchewan||Alberta|
|Total number of races||9||10||36||8|
|Total number of isolates||25||28||204||18|
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