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).

Table 1. Effect of barley yellow dwarf virus on yield (per 50 cm harvested row).

Table 2. Effect of barley yellow dwarf virus on 1,000-kernel weight (per 50 cm harvested row).

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.

References.

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 oxidase.

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.

J.A. Kolmer.

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 for Manitoba.

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 of 0-4: 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, and Lr18.

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
Lr1	92	97	99	100
Lr2a	12	4	16	17
Lr2c	48	54	18	72
Lr3	88	100	100	100
Lr9	0	0	0	0
Lr16	0	0	6	0
Lr24	0	0	21	11
Lr26	0	39	21	22
Lr3ka	44	71	36	0
Lr11	32	50	37	11
Lr17	40	18	46	50
Lr30	28	47	31	0
LrB	64	71	44	11
Lr10	72	93	97	100
Lr14a	76	50	100	50
Lr18	0	11	3	1
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
FBMN	2c,3,3ka,30,B,14a	8	0	0	-
MBBJ	1,3,10,14a	0	0	0	6
MBDS	1,3,17,B,10,14a	28	0	31	0
MBGJ	1,3,11,10,14a	12	7	1	0
MBRJ	1,3,3ka,11,30,10,14a	8	4	15	0
MCBJ	1,3,26,10,14a	0	0	1	17
MCDS	1,3,26,17,B,10,14a	0	18	11	0
MCRJ	1,3,26,3ka,11,30,10,14a	0	7	3	0
MCRK	1,3,26,3ka,11,30,10,14a,18	0	7	0	0
MDBJ	1,3,24,10,14a	0	0	1	1
MDRJ	1,3,24,3ka,11,30,10,14a	0	0	6	0
PBBT	1,2c,3,B,10,14a,18	0	0	0	6
PBDG	1,2c,3,17,10	0	0	0	44
PBDQ	1,2c,3,17,B,10	0	0	0	6
PBLQ	1,2c,3,3ka,B,10	16	25	0	0
PBRQ	1,2c,3,3ka,11,30,B,10	8	21	0	0
SBDD	1,2a,2c,17,14a	12	0	0	0
TBGJ	1,2a,2c,3,11,10,14a	0	0	2	11
TFBJ	1,2a,2c,3,24,26,10,14a	0	0	4	6
Total number of races		9	10	36	8
Total number of isolates		25	28	204	18

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