Hard Red Winter Wheat Cultivars Research Articles

Leaf Rust of Wheat: Pathogen Biology, Variation and Host Resistance

Rusts are important pathogens of angiosperms and gymnosperms including cereal crops and forest trees. With respect to cereals, rust fungi are among the most important pathogens. Cereal rusts are heteroecious and macrocyclic requiring two taxonomically unrelated hosts to complete a five spore stage life cycle. Cereal rust fungi are highly variable for virulence and molecular polymorphism. Leaf rust, caused by Puccinia triticina is the most common rust of wheat on a worldwide basis. Many different races of P. triticina that vary for virulence to leaf rust resistance genes in wheat differential lines are found annually in the US. Molecular markers have been used to characterize rust populations in the US and worldwide. Highly virulent races of P. triticina are selected by leaf rust resistance genes in the soft red winter wheat, hard red winter wheat and hard red spring wheat cultivars that are grown in different regions of the US. Cultivars that only have race-specific leaf rust resistance genes that are effective in seedling plants lose their effective resistance and become susceptible within a few years of release. Cultivars with combinations of race non-specific resistance genes have remained resistant over a period of years even though races of the leaf rust population have changed constantly.

Registration of ‘TAM 113’ Wheat

‘TAM 113’ (Reg. No. CV‐1081, PI 666125), a hard red winter wheat (Triticum aestivum L.) cultivar with experimental designation TX02A0252, was developed and released by Texas AgriLife Research in 2010. TAM 113 is an F5–derived line from the cross TX90V6313/TX94V3724 made at Vernon, TX in 1995. Both TX90V6313 and TX94V3724 are Texas experimental lines derived from the crosses TAM 200“S”/TX78A3345‐V34 and U1254‐1‐8‐1‐1/‘TAM 202’ (PI 561933), respectively. TAM 113 is an awned, medium maturing, semidwarf wheat with white glumes. It was released primarily for its excellent grain‐yield potential in both irrigated and dryland environments of the Texas High Plains; for its resistance to leaf rust (caused by Puccinia triticina Eriks.), stripe rust (caused by P. striiformis Westend.), and stem rust (caused by P. graminis Pers.:Pers f. sp. tritici Eriks. & E. Henn.); and for its good milling and exceptional bread‐baking characteristics. TAM 113 has a similar area of adaptation and grain‐yield potential as ‘TAM 111’ (PI 631352) and ‘TAM 112’ (PI 643143). However, compared with TAM 111, it has better leaf rust resistance and better bread‐baking qualities, and compared with TAM 112, it has better resistance to leaf and stripe rusts. TAM 113, with better milling and baking characteristics and resistance to leaf, stripe, and stem rusts, will provide a good complement to other hard red winter wheat cultivars for wheat producers in the southern Great Plains.

Registration of ‘Denali’ Wheat

‘Denali’ (Reg. No. CV‐1075, PI 664256) hard red winter wheat (Triticum aestivum L.) was developed by the Colorado Agricultural Experiment Station and released cooperatively by Colorado State University (CSU) and Kansas State University (KSU) in August 2011 through a marketing agreement with the Colorado Wheat Research Foundation. In addition to researchers at CSU and KSU, USDA‐ARS researchers at Manhattan, KS, St. Paul, MN, and Pullman, WA participated in its development. Denali was selected from the cross CO980829/‘TAM 111’ made in 2001 at Fort Collins, CO. CO980829 is an experimental line from CSU with the pedigree ‘Yuma’ (PI 559720)/PI 372129//CO850034/3/4*Yuma/4/NEWS12. TAM 111 (PI 631352) is a hard red winter wheat cultivar released by Texas A&M University in 2002. Denali was selected as an F5:6 line in July 2007 and assigned experimental line number CO050303‐2. Denali was released because of its superior grain yield under nonirrigated and irrigated production conditions in eastern Colorado, its grain volume weight, and its resistance to stripe rust (caused by Puccinia striiformis Westend. f. sp. tritici Eriks.).

Registration of ‘Byrd’ Wheat

’Byrd’ (Reg. No. CV‐1073, PI 664257) hard red winter wheat (Triticum aestivum L.) was developed by the Colorado Agricultural Experiment Station and released in August 2011 through a marketing agreement with the Colorado Wheat Research Foundation. In addition to researchers at Colorado State University (CSU), USDA‐ARS researchers at Manhattan, KS, St. Paul, MN and Pullman, WA participated in its development. Byrd was selected from the cross ‘TAM 112’/CO970547‐7 made in 2002 at Fort Collins, CO. TAM 112 (PI 643143) is a hard red winter wheat cultivar released by Texas A&M University in 2005. CO970547‐7 is an experimental line from CSU with the pedigree ‘Ike’ (PI 574488)/‘Halt’ (PI 584505). Byrd was selected as an F3:4 line in July 2006 and assigned experimental line number CO06424. Byrd was released because of its superior grain yield under nonirrigated and irrigated production conditions in eastern Colorado, its resistance to stripe (caused by Puccinia striiformis Westend. f. sp. tritici Eriks.) and stem rust (caused by Puccinia graminis Pers.:Pers f. sp. tritici Eriks. & E. Henn.), and its superior milling and bread‐baking quality attributes. The name Byrd was chosen in honor of former CSU wheat breeder and director of the CIMMYT Global Wheat Program, Dr. Byrd C. Curtis.

Registration of ‘Brawl CL Plus’ Wheat

‘Brawl CL Plus’ (Reg. No. CV‐1074, PI 664255) hard red winter wheat (Triticum aestivum L.) was developed by the Colorado Agricultural Experiment Station and released in August 2011 through a marketing agreement with the Colorado Wheat Research Foundation. In addition to researchers at Colorado State University (CSU), USDA‐ARS researchers at Manhattan, KS, St. Paul, MN, and Pullman, WA participated in its development. Brawl CL Plus was selected from the cross Teal 11A/‘Above’//CO99314 made in 2003 at Fort Collins, CO. Teal 11A is a proprietary hard red spring wheat germplasm line from BASF Corporation that carries a mutant allele at the Als2 locus (B genome) conferring tolerance to imazamox [2‐(4,5‐dihydro‐4‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐1h‐imidazol‐2‐yl)‐5‐(methoxymethyl)‐3‐pyridinecarboxylic acid] herbicide. Above (PI 631449) is a hard red winter wheat cultivar released by CSU in 2001 that carries a mutant allele at the Als1 locus (D genome) conferring tolerance to imidazolinone herbicides. CO99314 is an experimental line from CSU with the pedigree TX91V4931/‘Halt’ (PI 584505). Brawl CL Plus was selected as an F3:4 line in July 2006 and assigned experimental line number CO06052. Brawl CL Plus was released because it carries two mutations for enhanced tolerance to imazamox herbicide, is adapted under nonirrigated and irrigated production conditions in eastern Colorado, confers moderate resistance to stripe rust (caused by Puccinia striiformis Westend. f. sp. tritici Eriks.), and has good milling and bread‐baking quality attributes.

AC Readymade and AC Tempest, selections from Redwin hard red winter wheat

Thomas, J. B. and Graf, R. J. 2012. AC Readymade and AC Tempest, selections from Redwin hard red winter wheat. Can. J. Plant Sci. 92: 355–361. AC Readymade and AC Tempest are hard red winter wheat (Triticum aestivum L.) cultivars selected from the Montana cultivar ‘Redwin’ to conform to the kernel visual distinguishability requirements of the Canada Western Red Winter (CWRW) wheat class. AC Readymade and AC Tempest were registered in 1991 and 1999, respectively, following 3 yr of testing in the Western Winter Wheat Cooperative registration trials relative to various checks including Winalta, Norstar, CDC Clair and CDC Osprey. The survival characteristics of these cultivars demonstrated that they were well-suited to the relatively mild winter climate of southern Alberta. In this region of the prairies, AC Tempest had 4% higher grain yield than AC Readymade and was not significantly different from the other checks except Winalta, which was lower yielding. Both cultivars displayed relatively late maturity, moderate height, exceptional straw strength, high test weight, large kernels, high grain protein content and moderate resistance to common bunt. AC Tempest had significantly higher flour yield than AC Readymade.

Registration of ‘TAM 401’ Wheat

‘TAM 401’ (Reg. No. CV‐1056, PI 658500), a hard red winter wheat (Triticum aestivum L.) cultivar with the experimental designation TX03M1096, was developed and released by Texas AgriLife Research in 2008. TAM 401 is an F4‐derived line from the cross ‘Mason’ (PI 594044)/‘Jagger’ (PI 593688) made at College Station, TX in the fall of 1997. Mason is a soft red winter wheat cultivar released by AgriPro in 1996, and Jagger is a hard red winter wheat cultivar developed and released by Kansas State University in 1996. TAM 401 is an early maturing, apically awnletted wheat suitable for grain‐only, dual‐purpose, and graze‐out systems. TAM 401 was released primarily for its excellent grain yield potential across a wide range of environments in Texas; good fall and early winter forage potential; resistance to leaf rust (caused by Puccinia triticina Eriks.) and stripe rust (caused by P. striiformis Westend.); and acceptable hard red winter wheat end‐use quality. The proposed primary area of adaptation for TAM 401 will be the warmer and more humid areas such as South Texas, the Blacklands, and the Rolling Plains of Texas, where awnletted or apically awnletted hard red winter wheat cultivars with resistance to leaf rust and stripe rust are very limited.

Sunrise soft red winter wheat

Fowler, D. B. 2012. Sunrise soft red winter wheat. Can. J. Plant Sci. 92: 195–198. Sunrise is a high-yielding soft red winter wheat (Triticum aestivum L.) cultivar that is registered in the Canada Western General Purpose (CWGP) wheat class for production in western Canada. The CWGP wheat class was created in 2008 to encourage the development of cultivars to fill the high energy demands of the biofuel and livestock feed markets. The grain yield of Sunrise is similar to the high-yielding hard red and soft white winter wheat cultivars registered in the CWGP class. It has good stem rust, stripe rust, and tan spot resistance and moderate leaf rust resistance. High grain yield potential of low protein concentration grain combined with good agronomic and disease packages make Sunrise a good fit for the CWGP class.

Broadview hard red winter wheat

Graf, R. J., Thomas, J. B., Gaudet, D. A., Laroche, A. and Beres, B. L. 2012. Broadview hard red winter wheat. Can. J. Plant Sci. 92: 177–181. Broadview is a hard red winter wheat (Triticum aestivum L.) cultivar that is well adapted to the Canadian prairies. Compared with the check cultivars (CDC Falcon, CDC Harrier) in the Western Winter Wheat Cooperative registration trials, Broadview produced grain yield similar to CDC Falcon, the highest yielding check. In the eastern prairie rust area, it yielded 2% and 7% more grain than CDC Falcon and CDC Harrier, respectively. Broadview had good winter survival, early maturity, short straw, good lodging resistance and high test weight. It exhibited very good resistance to stem and leaf rust, and is believed to be the first winter wheat cultivar in North America to deploy the Lr21 leaf rust resistance gene. Broadview is eligible for all grades of the Canada Western General Purpose wheat class.

‘Duster’ Wheat: A Durable, Dual‐Purpose Cultivar Adapted to the Southern Great Plains of the USA

Winter wheat (Triticum aestivum L.) cultivars that gain commercial acceptance in the U.S. southern Great Plains must provide a definitive grain‐yield advantage, season‐long dependability in dual‐purpose management systems, effective resistance to foliar diseases, and tolerance to soil acidity. Our objective was to corroborate each of those strengths in the hard red winter (HRW) wheat cultivar ‘Duster’ (Reg. No. CV‐1065, PI 644016), which was released in 2006 by the Oklahoma Agricultural Experiment Station and the USDA‐ARS to complement ‘Endurance’ (Reg. No. CV‐994, PI 639233) with added dough strength and resistance to Wheat spindle streak mosaic. Duster was selected from a double cross, W0405/NE78488//W7469C/TX81V6187, made within the former Pioneer HRW‐wheat breeding program. Neither Duster nor its immediate parents are known to have a sib‐pair or parent‐offspring relationship with cultivars currently grown in the Great Plains. Duster is a descendent of an F2:3 line identified in Oklahoma in 1991, from which pedigree selection produced two F13‐derived lines that were composited to constitute breeder seed. The experimental line OK93P656H3299‐2C04 was tested in the 2005 and 2006 Southern Regional Performance Nursery, where it ranked first and fifth, respectively, for mean grain yield. Data from the Oklahoma Small Grains Variety Performance Tests were primarily used herein to demonstrate competitiveness for economic traits in a wide array of environmental conditions 5 yr following Duster's release.

Broadview hard red winter wheat

Graf, R. J., Thomas, J. B., Gaudet, D. A., Laroche, A. and Beres, B. L. 2012. Broadview hard red winter wheat. Can. J. Plant Sci. 92: 177-181. Broadview is a hard red winter wheat (Triticum aestivum L.) cultivar that is well adapted to the Canadian prairies. Compared with the check cultivars (CDC Falcon, CDC Harrier) in the Western Winter Wheat Cooperative registration trials, Broadview produced grain yield similar to CDC Falcon, the highest yielding check. In the eastern prairie rust area, it yielded 2% and 7% more grain than CDC Falcon and CDC Harrier, respectively. Broadview had good winter survival, early maturity, short straw, good lodging resistance and high test weight. It exhibited very good resistance to stem and leaf rust, and is believed to be the first winter wheat cultivar in North America to deploy the Lr21 leaf rust resistance gene. Broadview is eligible for all grades of the Canada Western General Purpose wheat class.

First Detection in North America of Virulence in Wheat Leaf Rust (Puccinia triticina) to Seedling Plants of Wheat with Lr21.

Leaf rust resistance gene Lr21 is present in hard red spring wheat (Triticum aestivum) cultivars grown in Minnesota, North Dakota, South Dakota, Manitoba, and Saskatchewan. Isolates of Puccinia triticina, the causal organism of wheat leaf rust, with virulence to this gene have not been previously detected in annual virulence surveys in the United States. (2). In 2010, hard red spring wheat cvs. Faller, RB07 (1), and Glenn, all with Lr21, had 0 to 5% levels of leaf rust severity, which was higher than in previous years in research plots in North Dakota and Minnesota. Leaf rust collections from wheat cultivars and germplasm lines with Lr21 at three locations in Minnesota and North Dakota were increased on plants of the leaf rust susceptible wheat Thatcher and the Thatcher line with Lr21. Single uredinia from the collections were isolated and increased on seedlings of Thatcher. The single uredinial isolates were inoculated to 7- to 8-day-old seedling plants of the set of 19 differential lines that are currently used in the leaf rust virulence surveys (2). Thatcher lines with Lr3bg, Lr14b, Lr20, and Lr23 were also tested. The isolates were also inoculated to seedling plants of hard red spring wheat cultivars with Lr21: Glenn, Steele-ND, Faller, RB07, Amidon, AC Cora, and McKenzie (3). Previous standardized methods for growing seedling plants, increase of rust isolates, inoculation, incubation, and evaluation of infection types (IT) were used (2). All tests with the Thatcher differential lines and the cultivars with Lr21 were repeated at least twice. Virulence phenotypes were described based on virulence to the 19 differentials in the P. triticina virulence nomenclature system used in the United States. (2). Two virulence phenotypes, TFBJQ and TFBGQ, with virulence to Lr21 were found at the three locations. TFBJQ is virulent (IT 3 to 4) to genes Lr1, 2a, 2c, 3, 10, 14a, 14b, 20, 21, 24, 26, 28, and avirulent (IT 0 to 2+) to genes Lr3ka, Lr3bg, Lr9, Lr11, Lr17, Lr18, Lr30, LrB, and Lr39/41. TFBGQ was avirulent to Lr14a and Lr20, but identical to TFBJQ for virulence and avirulence to the other resistance genes. Isolates of both phenotypes were virulent on seedlings of Faller, Glenn, RB07 (1), Steele-ND, AC Cora, and Amidon. McKenzie had IT of 2+ due to the additional presence of Lr16 (3). Both TFBJQ and TFBGQ have intermediate IT of 2+ to Lr16; IT 2+3 to Lr23, and are completely virulent to Lr1, Lr2a, and Lr10 that are present in hard red spring wheat cultivars. Both phenotypes have high IT to Lr24 and Lr26 that are present in soft red winter wheat and hard red winter wheat cultivars. The Lr21 virulent phenotypes likely arose by mutation from the group of P. triticina genotypes in the simple sequence repeat group NA-5 (4) that have intermediate IT of ;2- to ;2+ to the Thatcher line with Lr21. P. triticina isolates with virulence to Lr21 are a new threat to wheat production since in 2010 more than 50% of the hard red spring wheat acreage in Minnesota and North Dakota relied on Lr21 for effective resistance to leaf rust.

Accipiter hard red winter wheat

Fowler, D. B. 2011. Accipiter hard red winter wheat. Can. J. Plant Sci. 91: 363–365. Accipiter is an intermediate height, high-yielding, winter wheat (Triticum aestivum L.) cultivar with good stem and moderate leaf rust resistance that is registered for production in western Canada. It is a hard red winter wheat cultivar that is eligible for grades of the Canada Western General Purpose (CWGP) wheat class. The CWGP class was created in 2007 to encourage the development of cultivars to fill the high energy demands of the biofuel and livestock feed markets in western Canada. The grain yield of Accipiter was 114% of the Canada Western Red Winter Wheat class grain quality check cultivar, CDC Osprey, and 103% of the high-yielding check, CDC Falcon. High grain yield potential combined with good agronomic and disease packages make Accipiter a good fit for the CWGP class.

Impact of Wheat Grain Selenium Content Variation on Milling and Bread Baking

ABSTRACTSelenium (Se) is an essential micronutrient in animals. High levels of Se can accumulate in wheat grain, but it is not clear how high Se affects milling or baking. Low and high Se grain from the same hard red winter wheat cultivar was milled and used for breadbaking studies and Se analysis. Mill stream yields from the low and high Se wheat were comparable, as were flour yields. The amount of total grain Se retained in the flour mill streams was 71.2 and 66.4% for the low and high Se wheat, respectively. Proportionally, Se content in the bran, shorts, and the first reduction flour stream in high Se wheat was higher by 13–20% compared to the low Se wheat. Flour quality parameters including protein content, ash content, and farinograph traits were similar in low and high Se flours, although high Se flour mill streams exhibited lower farinograph stability. Breadbaking evaluations indicated that high Se had a deleterious effect on loaf volume. There was no evidence of significant Se loss after breadbaking with either low or high Se flour.

Development of a PCR assay and marker-assisted transfer of leaf rust resistance gene Lr58 into adapted winter wheats

Leaf rust resistance gene Lr58 derived from Aegilops triuncialis L. was transferred to the hard red winter wheat (HRWW) cultivars Jagger and Overley by standard backcrossing and marker-assisted selection (MAS). A co-dominant PCR-based sequence tagged site (STS) marker was developed based on the sequence information of the RFLP marker (XksuH16) diagnostically detecting the alien segment in T2BS·2BL-2tL(0.95). STS marker Xncw-Lr58-1 was used to select backcross F1 plants with rust resistance. The co-dominant marker polymorphism detected by primer pair NCW-Lr58-1 efficiently identified the homozygous BC3F2 plants with rust resistance gene Lr58. The STS marker Xncw-Lr58-1 showed consistent diagnostic polymorphism between the resistant source and the wheat cultivars selected by the US Wheat Coordinated Agricultural Project. The utility and compatibility of the STS marker in MAS programs involving robust genotyping platforms was demonstrated in both agarose-based and capillary-based platforms. Screening backcross derivatives carrying Lr58 with various rust races at seedling stage suggested the transferred rust resistance in adapted winter wheats is stable in both cultivar backgrounds. Lr58 in adapted winter wheat backgrounds could be used in combination with other resistance genes in wheat rust resistance breeding.

Peregrine hard red winter wheat

Peregrine is a medium tall, high-yielding, stem and leaf rust resistant winter wheat (Triticum aestivum L.) that is registered for production in western Canada. It is a hard red winter wheat cultivar that is eligible for grades of the Canada Western General Purpose (CWGP) wheat class. The CWGP class was created in 2007 to encourage the development of cultivars to fill the high energy demands of the biofuel and livestock feed markets in western Canada. In Manitoba and Saskatchewan, the grain yield of Peregrine was 117% of the Canada Western Red Winter Wheat Class grain quality check cultivar, CDC Osprey, and 106% of the high-yielding check, CDC Falcon. High grain yield potential and a high level of rust resistance mean that Peregrine provides a good fit for the CWGP class.

CDC Buteo hard red winter wheat

CDC Buteo is a hard red winter wheat (Triticum aestivum L.) cultivar that is eligible for grades of the Canada Western Red Winter Wheat class. It is an intermediate height cultivar with moderate stem and leaf rust resistance and good winter hardiness and grain yield potential. It is adapted to the western Canadian prairies where its agronomic and disease package combined with an excellent grain quality profile has resulted in wide commercial acceptance in Saskatchewan. CDC Buteo was made the wheat quality standard for the Central Winter Wheat Co-operative Registration Trials in 2008.Key words: Triticum aestivum L., cultivar description, wheat (winter)

Effects of Wheat streak mosaic virus on Root Development and Water-Use Efficiency of Hard Red Winter Wheat.

Greenhouse and field studies were conducted to determine the effects of Wheat streak mosaic virus (WSMV), a member of the family Potyviridae, on root development and water-use efficiency (WUE) of two hard red winter wheat (Triticum aestivum) cultivars, one susceptible and one resistant to WSMV. In the greenhouse studies, wheat cultivars were grown under three water regimes of 30, 60, and 80% soil saturation capacity. After inoculation with WSMV, plants were grown for approximately 4 weeks and then harvested. Root and shoot weights were measured to determine the effect of the disease on biomass. In all water treatments, root biomass and WUE of inoculated susceptible plants were significantly less (P < 0.05) than those of the noninoculated control plants. However, in the resistant cultivar, significance was only found in the 30 and 60% treatments for root weight and WUE, respectively. Field studies were also conducted under three water regimes based on reference evapotranspiration rates. Significant reductions in forage, grain yield, and crop WUE were observed in the inoculated susceptible plots compared with the noninoculated plots. Both studies demonstrated that wheat streak mosaic reduces WUE, which is a major concern in the Texas Panhandle because of limited availability of water.

Appearance of Powdery Mildew of Wheat Caused by Blumeria graminis f. sp. tritici on Pm17-Bearing Cultivars in North Carolina.

Pm17 is a gene for resistance to powdery mildew caused by Blumeria graminis (DC.) E.O. Speer f. sp. tritici. The gene was first confirmed in the wheat-rye translocation cultivar Amigo (1). In Amigo, the translocation is T1AL-1RS and the 1RS arm has the gene Pm17. In the mid-Atlantic United States, at least two widely deployed soft red winter wheat (Triticum aestivum L.) cultivars, McCormick (2) and Tribute (3), possess Pm17 inherited from Amigo. Before 2009, low frequencies of mostly intermediate virulence to Pm17 were detected among isolates from research plots of highly susceptible cultivars (4), but Pm17-bearing cultivars remained immune to mildew in the field. In April 2009, moderately severe powdery mildew was observed for the first time throughout plots of McCormick, Tribute, and other cultivars in both Kinston and Raleigh, NC. At Kinston, Pm17 virulence was observed at two research sites, separated by approximately 10 km, throughout plots of Amigo, McCormick, Tribute, and the hard red winter wheat cultivar TAM 303, which also contains Pm17. In the same month, virulence to Pm17 was observed in Raleigh throughout rows and plots of Amigo and TAM 303. In Kinston and Raleigh, ratings of powdery mildew severity on the Pm17-containing cultivars were 4 or 5 on a scale of 0 to 9, with 0 being the absence of mildew pustules and 9 the most severe mildew infection. Mildew was observed on leaves of all ages. Mildewed leaves were collected from field plots of all four Pm17-bearing cultivars, and an assay to confirm Pm17 virulence was conducted in the laboratory. Mixed-isolate cultures were derived from the leaves and a detached-leaf assay was performed using Amigo, which is the standard Pm17 differential (4). All tested cultures were fully to moderately virulent on Pm17 and all were fully virulent on the susceptible control Chancellor. In the field, chasmothecia (sexual fruiting bodies) were observed on Pm17-bearing cultivars. Together with the quantitatively varying Pm17 virulence detected in the laboratory assay, this suggests that multiple strains of Pm17-virulent B. graminis f. sp. tritici may be present in the field, although that has not yet been demonstrated. Pm17 has protected wheat from powdery mildew over a substantial area in the mid-Atlantic United States. The loss of Pm17 is the most important virulence shift in the U.S. wheat powdery mildew population since Pm4a became ineffective around 2002. Isolates virulent to Pm17 can be expected to appear and multiply in wheat-producing states of the mid-Atlantic United States, including Delaware, Maryland, Virginia, North Carolina, South Carolina, and Georgia. Thus, the urgency of developing and releasing wheat cultivars with other sources of effective mildew resistance is heightened.

Wheat–Thinopyrum Intermedium Recombinants Resistant to Wheat Streak Mosaic Virus and Triticum Mosaic Virus

To date, only one gene conferring resistance to Wheat streak mosaic virus (WSMV) designated as Wsm1 was transferred from Thinopyrum intermedium (Host) Barkworth and Dewey to wheat (Triticum aestivum L.) in the form of a compensating Robertsonian translocation T4DL·4JsS. Wsm1 confers high levels of resistance to WSMV under field conditions; however, in certain genetic backgrounds and environments, the presence of the T4DL·4JsS translocation reduces agronomic performance. The objective of this study was to shorten the Th. intermedium segment in the T4DL·4JsS translocation. We recovered one proximal (rec36) and four distal (rec45, rec64, rec87, rec213) primary recombinants. Genomic in situ hybridization and molecular marker analyses determined the size of the Th. intermedium segments in the distal recombinants to be about 20% of the 4DS‐4JsS arm. All primary recombinant stocks, together with appropriate controls, were evaluated for their resistance to WSMV and Triticum mosaic virus (TriMV) in greenhouse tests. Whereas the distal recombinants rec45, rec64, rec87, and rec213 were resistant to both WSMV and TriMV at low temperatures of 18°C, the proximal recombinant rec36 reacted susceptible, which mapped the Wsm1 gene to the distal 20% of the 4DS‐4JsS arm. We successfully shortened the Th. intermedium segment while still retaining the Wsm1 gene. The T4DL·4DS‐4JsS recombinant chromosome of the rec213 stock was transferred to adapted Kansas hard red winter wheat cultivars.