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22 April 2022 AAC Coldfront hard red winter wheat
R.J. Graf, B.L. Beres, A. Laroche, R. Aboukhaddour, D.G. Humphreys, R.J. Larsen, H.S. Randhawa, N.A. Foroud, H.S. Sidhu
Author Affiliations +

AAC Coldfront is a hard red winter wheat (Triticum aestivum L.) cultivar with broad adaptation and excellent performance in all production areas of western Canada. Eligible for grades of Canada Western Red Winter (CWRW) wheat, AAC Coldfront was evaluated in the Western Canadian Winter Wheat Cooperative registration trials relative to CDC Buteo, Emerson, Moats, and AAC Elevate. Based on 32 replicated trials over 3 years (2017/2018–2019/2020), AAC Coldfront produced significantly more grain than all of the checks (108–115%) at a protein concentration similar to the check mean, suggesting an improved capacity to convert soil moisture and nutrients into grain under a wide range of western Canadian field conditions. AAC Coldfront expressed very good winter survival, medium to late maturity, short to moderate height, excellent lodging resistance, and high test weight. AAC Coldfront was rated resistant to stem, leaf, and stripe rust, intermediate in resistance to Fusarium head blight, and susceptible to common bunt. It became a check for western Canadian winter wheat registration trials in 2021/2022.


AAC Coldfront hard red winter wheat (Triticum aestivum L.) was developed at the Lethbridge Research and Development Centre (LeRDC) of Agriculture and Agri-Food Canada (AAFC) in Lethbridge, AB. Tested as LR535 and W601, AAC Coldfront was granted registration No. 9507 by the Variety Registration Office, Plant Production Division, Canadian Food Inspection Agency on 25 Feb. 2022. Plant Breeders’ Rights application No. 22-10774 was accepted for filing on 12 Jan. 2022.

AAC Coldfront showed broad adaptation across western Canada, expressing very high grain yield and winter survival combined with desirable agronomic traits, very good resistance to all species of wheat rust, intermediate resistance to Fusarium head blight, and end-use quality acceptable for the Canada Western Red Winter (CWRW) wheat class. AAC Coldfront replaced CDC Buteo (Fowler 2010) as a CWRW registration trial check in 2021/2022.

Pedigree and Breeding Method

AAC Coldfront was selected from the three-way cross Norstar/CDC Falcon//LF1318, completed in 2008. Norstar (Grant 1980) and CDC Falcon (Fowler 1999) are registered Canadian cultivars developed at AAFC LeRDC and the University of Saskatchewan Crop Development Centre, respectively. LF1318 was an experimental line developed at AAFC LeRDC, selected from a McClintock/Radiant doubled-haploid population and tested in the Western Canadian Winter Wheat Cooperative (WWWC) registration trial as W455 (Brûlé-Babel 2003; Thomas et al. 2012). An expanded ancestry of AAC Coldfront is presented in Fig. 1.

Fig. 1.

Expanded ancestry of AAC Coldfront hard red winter wheat.


Following growth of 60 F1 seeds in a greenhouse, about 6000 F2 plants were grown in a large, sparsely seeded bulk plot at Lethbridge in 2010, from which 138 spikes were selected and planted as F3 head rows. In 2011, approximately 250 spikes were selected from rows expressing good winter survival and spring vigour, attractive plant type with short to moderate plant height and stiff straw, and resistance to stripe rust (Puccinia striiformis Westend.). These spikes were threshed in bulk and seeded as several plots in Saskatoon, SK; in 2012, 153 spikes were selected based on winter survival and plant type. Each spike was planted as a row in an inoculated stem rust (Puccinia graminis Pers.: Pers. f.sp. tritici Eriks. & E. Henn.) and leaf rust (Puccinia triticina Eriks.) nursery on the University of Manitoba campus in Winnipeg, MB; 115 spikes were selected from among the resistant rows in 2013 and planted as F5:6 observation rows in Lethbridge. In 2014, 40 of the 115 rows were harvested and seeded in single replicate irrigated preliminary trials in Lethbridge, as well as the stem and leaf rust nursery in Winnipeg, and an inoculated stripe rust nursery in Lethbridge. Based on the resistance expressed by parent LF1318, wheat curl mite (WCM, Aceria tosichella Keifer) reaction was also evaluated. Promising agronomic characteristics, resistance to all wheat rusts, and acceptable end-use quality prompted replicated, multi-location testing of 13 lines in 2016 and three lines in 2017. Further examination of the resistance to stem rust, leaf rust, stripe rust, Fusarium head blight (FHB) {caused by Fusarium graminearum Schwabe [teleomorph Gibberella zeae (Schwein.) Petch]}, common bunt [Tilletia tritici (Bjerk.) G. Wint. in Rabenh. and Tilletia laevis Kühn in Rabenh.], and wheat curl mite were also conducted in both years. Following 14 site-years of replicated field tests across western Canada and 2 years of full end-use quality analysis, a line designated LR535 entered the WWWC registration trial as W601 and was evaluated for 3 years (2017/2018 to 2019/2020). It was retained in the trial in 2020/2021 to provide contiguous annual data as it transitioned to become a check, starting in 2021/2022. For additional details, please see Table 1.

Table 1.

AAC Coldfront hard red winter wheat selection and evaluation history.



Grain yield and agronomics

The performance of AAC Coldfront was assessed in the WWWC registration trials relative to CDC Buteo, Emerson (Graf et al. 2013), Moats (Fowler 2012), and AAC Elevate (Graf et al. 2015). Agronomic test sites across western Canada were in Alberta (Beaverlodge, Lacombe, Lethbridge, Olds, Warner), Saskatchewan (Indian Head, Melfort, Saskatoon, Swift Current), and Manitoba (Brandon, Carman, Portage la Prairie, Winnipeg), through the collaborative efforts of AAFC, Alberta Agriculture and Forestry, and the University of Manitoba. Analyses of variance were conducted using a combined mixed effects model where environments were treated as random effects and genotypes were fixed. The least significant difference (LSD) generated from the analysis of variance was used to identify significant differences from the check cultivars.

Data collected from 32 sites over 3 years established the agronomic performance of AAC Coldfront in western Canada. The overall mean grain yield of AAC Coldfront was 11% higher than the CWRW check mean (P ≤ 0.05). Relative to specific checks, AAC Coldfront was significantly higher yielding than CDC Buteo (+13%), Emerson (+15%), Moats (+9%), AAC Elevate (+8), and CDC Falcon (+14%) (P ≤ 0.05). CDC Falcon is not a CWRW check but is reported because of its familiarity to Manitoba and eastern prairie producers. On a provincial basis, AAC Coldfront had significantly higher grain yield than all of the checks in Alberta and Saskatchewan. In Manitoba, AAC Coldfront was significantly higher yielding than CDC Buteo and Moats (P ≤ 0.05), and marginally higher than Emerson and AAC Elevate (P ≤ 0.06) (Table 2).

Table 2.

Grain yield (t·ha−1) of AAC Coldfront and the check cultivars, Western Canadian Winter Wheat Cooperative registration trial (2018–2020).


AAC Coldfront expressed winter survival similar to the CWRW check cultivars and equal to CDC Buteo, the best check. The heading and maturity dates for AAC Coldfront were earlier and later than the CWRW check means, respectively (P ≤ 0.05), which reflects a 2 day longer grain-filling period. AAC Coldfront was similar to AAC Elevate for heading date and to Emerson for maturity date. The plant height of AAC Coldfront was equal to AAC Elevate and shorter than the remaining CWRW checks (P ≤ 0.05). Lodging resistance was superior to CDC Buteo and Moats (P ≤ 0.05). The test weight and seed weight of AAC Coldfront were within the range of the CWRW checks. AAC Coldfront produced grain with a protein concentration similar to the check mean and equal to CDC Buteo and Moats. Grain protein yield, measured by multiplying grain yield × grain protein concentration at each site, was 10% higher than the check mean and 7% higher than Emerson, the best check (≤ 0.001), suggesting that AAC Coldfront has a much improved capacity to convert soil moisture and nutrients into grain under a wide range of western Canadian field conditions (DePauw et al. 1989; Ortiz-Monasterio et al. 2001) (Table 3). Research into the nature of this improvement may be valuable as plant breeders and other scientists strive to improve the productivity, climate resilience, and profitability of the Canadian agriculture sector.

Table 3.

Agronomic and seed characteristics of AAC Coldfront and the check cultivars, Western Canadian Winter Wheat Cooperative registration trial (2018–2020).


Disease resistance

During registration testing, resistance to the wheat diseases of major economic importance in the eastern and western prairies (Aboukhaddour et al. 2020) was assessed by AAFC and the University of Manitoba using methodologies described in the Operating Procedures (Appendix E) of the Prairie Recommending Committee for Wheat, Rye, and Triticale (PRCWRT; Supplementary checks were included in the various nurseries to aid in making accurate assessments. Adult plant reactions to stem and leaf rust were determined in artificially inoculated field nurseries conducted by the University of Manitoba in Winnipeg using race composites supplied by the AAFC Morden Research and Development Centre (MRDC), and reported using the modified Cobb scale (Peterson et al. 1948). The stem rust races used for 1 or more years included MCC (P0001), QTH (P0005), RHT (P0002), RKQ (P0003), RTH (P0007), TMR (P0006), and TPM (P0004) (Fetch et al. 2021). The leaf rust races were a representative mixture collected in western Canada during the previous field season (McCallum et al. 2021). Seedling reactions to individual races of stem and leaf rust prevalent in Canada were also determined under controlled-environment conditions by personnel at AAFC, MRDC. The races of stem rust were the same as those used in the field nurseries, whereas the leaf rust races used for 1 or more years included MBDS (12-3), MBRJ (128-1), MGBJ (74-2), TDBG (06-1-1), TDBG (11-180-1), and TJBJ (77-2). Stripe rust ratings were determined in irrigated, inoculated nurseries at AAFC LeRDC, using races prevalent in southern Alberta during the previous year (Puchalski and Gaudet 2011). The reaction to common bunt was also estimated in nurseries conducted at AAFC LeRDC by planting into cold soil in mid-October. All seed was mixed with a blend of bunt spores that included races L1, L16, T1, T6, T13, and T19 (Hoffman and Metzger 1976; Gaudet and Puchalski 1989). FHB response was determined by staff at the University of Manitoba in Carman and Winnipeg, and at the AAFC Ottawa Research and Development Centre in Ottawa, using mist-irrigated field nurseries with three replicates. Each line was spray-inoculated with an F. graminearum macroconidial suspension at 50% anthesis and again 3–4 days later. The inoculum had a concentration of 50 000 macroconidia·mL−1 and contained equal amounts of two 3-acetyldeoxynivalenol (3-ADON) and two 15-acetyldeoxynivalenol (15-ADON) producing chemotypes. Visual index (% incidence × % severity / 100) was typically recorded 18 to 21 days after anthesis or when symptoms were well developed (Gilbert and Woods 2006; Cuthbert et al. 2007). At maturity in Carman and Winnipeg, a 50 g sample from each row was used to determine the percentage of Fusarium-damaged kernels (FDK) and to quantify the deoxynivalenol (DON) content using enzyme-linked immunosorbent assays (ELISA). The response to WCM infestation was conducted annually at AAFC LeRDC by exposing several replicates of 10 to 15 seedlings to non-viruliferous mites for 2 to 3 weeks under controlled-environment conditions, with ratings based on pronounced leaf rolling and looping of newly emerging leaves (Thomas and Conner 1986).

The PRCWRT Disease Evaluation Team summarized 3 years of disease ratings for AAC Coldfront as resistant to the prevalent races of stem rust, leaf rust, and stripe rust, intermediate in resistance to FHB, and susceptible to common bunt (Tables 4 and 5). AAC Coldfront did not express wheat curl mite resistance (data not presented).

Table 4.

Disease reactions of AAC Coldfront and the check cultivars, Western Canadian Winter Wheat Cooperative registration trials (2018–2020).


Table 5.

Fusarium head blight (FHB) reaction of AAC Coldfront, check cultivars and supplementary checks, Western Canadian Winter Wheat Cooperative registration trials (2018–2020).


End-use quality

End-use quality analyses were conducted annually at the Canadian Grain Commission, Grain Research Laboratory, following protocols of the American Association of Cereal Chemists (2000). Following Canadian Grain Commission determination of grain grade and protein concentration for the check cultivars at all of the agronomic test locations, a common site blending formula for the checks and all experimental lines was provided so as to produce composite samples where the mean protein concentration of the checks was approximately 12.5%. Grain from test sites with serious down-grading factors was not included in the quality composites.

Following 3 years (2018–2020) of end-use suitability testing, the PRCWRT Quality Evaluation Team considered AAC Coldfront eligible for grades of CWRW wheat. Based on the 3-year means, AAC Coldfront was within tolerances relative to the check means for most characteristics. Notably, AAC Coldfront had superior flour yield (0.5% ash), with improved (lower) ash content. AAC Coldfront was flagged for lower farinograph absorption but was within the range of the checks (Table 6).

Table 6.

End-use quality characteristics of AAC Coldfront and the check cultivars, Western Canadian Winter Wheat Cooperative registration trials (2018–2020).


Other Characteristics


Leaf sheath and blade glabrous.


Juvenile growth habit prostrate; flag leaf blade glabrous, medium to strong glaucosity, mid-long, mid-wide, absent or very low frequency of recurved leaves; flag leaf sheath glabrous, strong glaucosity; absent or very weak auricle anthocyanin colouration; culm neck straight to weakly curved, hollow, upper most node pubescence absent or very sparse, weak glaucosity, anthocyanin intensity at maturity absent or very weak.


Awned, tapering, medium density, medium length, medium glaucosity, yellow, inclined, awns white, medium spreading to spreading; lower glume mid-long, mid-wide, glabrous; glume shoulders primarily strongly sloping, width very narrow to narrow; glume beak short to medium long; resistant to shattering.


Medium red, texture medium hard, medium size.

Maintenance and Distribution of Pedigreed Seed

A standard head-row derivation approach was used to produce Breeder Seed of AAC Coldfront. In fall 2019, spikes were collected from rogued F5:11 increase plots, threshed individually, and planted in Lethbridge under isolation. Unfortunately, an intense blizzard on 28–29 Sept. 2019 necessitated late seeding into wet soil, resulting in uneven emergence and poor establishment of the rows, which was further exacerbated by intense winds and soil erosion in early spring. These unfavourable conditions reduced the number of available rows from 116 to 75 with reasonable growth. In the interest of developing uniform Breeder Seed, 30 of the 75 head rows were eliminated due to what appeared to be minor height and maturity differences, some of which were likely the result of variable times to emergence, often within the same row. The remaining 45 rows were harvested individually and sent to the AAFC Seed Increase Unit at Indian Head for planting. In 2021, 5 of the 45 potential breeder lines were eliminated due to extreme drought and gopher damage. Three lines were eliminated based on variable height. The remaining 37 breeder lines at the F13 generation were inspected, harvested in bulk, and cleaned to produce 395 kg of Breeder Seed, which was distributed to pedigreed seed growers in fall 2021. Breeder Seed of AAC Coldfront will be maintained by the AAFC Seed Increase Unit. All other pedigreed seed classes will be multiplied and distributed by SeCan Association, 400–300 Terry Fox Drive, Ottawa, ON, K2K 0E3, Canada. Tel: 1-800-764-5487; Fax: 613-592-9497; e-mail:


Sincere appreciation is expressed to the dedicated staff at the AAFC LeRDC who contributed to the development of AAC Coldfront winter wheat, in particular: B. Postman, D. Quinn, J. Prus, M. Fast, L. Kneeshaw, D. Pearson, E. Amundsen, T. Despins, C. Parent, S. Pahl, M. Cradduck, and the many summer students over the years. The authors also recognize the support provided by numerous AAFC personnel working at research sites in Lethbridge, Beaverlodge, Swift Current, Saskatoon, Indian Head, Melfort, Brandon, Portage la Prairie, Winnipeg, and Ottawa; the provision of inoculated stem/leaf rust and FHB nurseries by A. Brûlé-Babel at the University of Manitoba; and all contributors to the Western Canadian Winter Wheat Cooperative registration trials. Thanks are also extended to H. Naeem and staff of the AAFC Seed Increase Unit at Indian Head for their care and attention in producing and maintaining the Breeder Seed of AAC Coldfront. In addition to funding from AAFC, financial assistance from the following producer and industry groups is gratefully acknowledged: the Western Grains Research Foundation producer check-off on wheat, the Ducks Unlimited Canada administered Western Winter Wheat Initiative, the Canadian Wheat Research Coalition, the Alberta Wheat Commission, the Saskatchewan Winter Cereals Development Commission, Winter Cereals Manitoba, and the Alberta Crop Industry Development Fund.



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© 2022 Her Majesty the Queen in Right of Canada, as represented by the Minister of Agriculture and Agri-Food Canada.
R.J. Graf, B.L. Beres, A. Laroche, R. Aboukhaddour, D.G. Humphreys, R.J. Larsen, H.S. Randhawa, N.A. Foroud, and H.S. Sidhu "AAC Coldfront hard red winter wheat," Canadian Journal of Plant Science 102(3), 785-795, (22 April 2022).
Received: 25 February 2022; Accepted: 11 April 2022; Published: 22 April 2022
blé (d’hiver)
cold tolerance
Cultivar description
description de cultivar
disease resistance
grain yield
rendement grainier
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