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Semiarid Prairie Agricultural Research Centre, Agriculture and Agri-Food Canada, Box 1030, Swift Current, SK, Canada S9H 3X2
* Corresponding author (knoxr{at}agr.gc.ca).
ABSTRACT
DT676 (Reg. No. GP-838, PI 650845), initially identified as P9162-BJ08*B, is a durum wheat [Triticum turgidum L. subsp. durum (Desf.) Husn.] line released in 2007 by Agriculture and Agri-Food Canada, Semiarid Prairie Agricultural Research Centre in Swift Current, SK, Canada. Well adapted to the drier regions of the northern Great Plains, DT676 is a source of resistance to the prevalent Canadian prairie races of loose smut [caused by Ustilago tritici (Pers.) Rostr.].
DT676 (Reg. No. GP-838, PI 650845) durum wheat [Triticum turgidum L. subsp. durum (Desf.) Husn.] was released in 2007 by Agriculture and Agri-Food Canada (AAFC), Semiarid Prairie Agricultural Research Centre in Swift Current, SK, Canada. Currently, durum wheat cultivars registered in Canada are susceptible to loose smut [caused by Ustilago tritici (Pers.) Rostr.] (SAFRR, 2007). Initially identified as P9162-BJ08*B, DT676 is adapted to the drier regions of the northern Great Plains and has resistance to the predominant races T32, T33, and minor race T26 of loose smut found on the Canadian prairie (Menzies et al., 2003). DT676 derives from the cross DT369/3*‘Kyle’/4/Kyle//VIR51658/2*‘Medora’/3/Kyle. VIR51658/2*Medora, a BC1F4 selection resistant to loose smut race T33, was contributed by D. Leisle, Cereal Research Centre, AAFC. VIR51658 (CN 17992) was further tested and found to be completely resistant to individual races T26, T32, and T33 (Menzies et al., 2003). Kyle (PI 537310) is adapted to the dry prairie (McLeod et al., 1991b) and was the Canadian durum class standard at the time of crossing. Medora (PI 496260) (Leisle, 1986) is a Canadian cultivar contributing strong straw. DT369 (PI 546362) is a high-yielding, strong-gluten, semidwarf durum wheat (McLeod et al., 1991a).
Methods
Early Generation Population Development
DT676 was developed by a combination of backcrossing with a modified pedigree method. The VIR51658/2*Medora selection was crossed to Kyle in 1988, and the crossed seed was needle inoculated with loose smut race T33 as described by Nielsen and Thomas (1995). A backcross, with Kyle as the male, was made with healthy F1 plants. The BC1F1 crossed seed was increased at Brawley, CA, winter nursery as unreplicated spike rows, and BC1F2 seed within each spike row was bulked at harvest. Ten BC1F2 bulks were grown in two replicate randomized complete block design tests near Swift Current and Regina, SK. Plots were approximately 2.76 m2 with four rows of approximately 200 seeds each. Two spikes from one plant were needle inoculated, one with race T33 and a second with race T26. The inoculated spikes were collected before harvest of the remainder of the plot. Yield, relative maturity, relative height, lodging, and quality tests of percentage protein, mixograph development time, mixograph peak height, and pigment (AACC, 2000) were recorded and compared with checks Medora, ‘Sceptre’ (PI 584833), ‘Wakooma’ (CN33718), ‘Wascana’ (CN33617), Kyle, DT367, and DT369. Lines with shorter stature based on relative height scores and other traits similar to the checks were selected.
The Kyle//VIR51658/2*Medora/3/Kyle BC1F3 inoculated seed was grown as spike rows in the greenhouse with two seeds from each inoculated spike grown in pots for crossing in a growth room. Healthy plants in pots that corresponded to healthy spike rows were crossed with DT369/3*Kyle BC2F2 plants in early 1991. The DT369/3*Kyle BC2F2 had been treated with 2.887 µmol L–1 gibberellic acid and insensitive (semidwarf) selections (Gale and Gregory, 1977) were used as parents in the cross. The crossed seed was needle inoculated with a mix of race T26 and T33 and grown in pots in the greenhouse. Healthy F1 plants were selected. One spike from each F1 plant was needle inoculated with the mixture of races T33 and T26, and one spike on the same plant was needle inoculated with race T32. Seed of the spike inoculated with the race mixture was grown in spike rows in the greenhouse to prevent spread of potential recombinant virulent types and rated. Race T32 inoculated spikes were grown in 1.5-m spike rows with 22 cm between rows in the field near Swift Current.
The 229 spike rows representing 18 F1-derived F2 families were randomized and seeded with five sets of check cultivars placed within the test after every 46 spike rows. The agronomic and quality checks were Wakooma, ‘Plenty’ (PI 584832), Kyle, DT367, and DT369. Lines with a loose smut incidence of 35% or less to the race T26/T33 mixture and to race T32, that matured within 101 d, were less than 105 cm tall, and showed acceptable straw strength, robustness, and general plant health were selected. Concurrent with the testing of experimental lines, disease checks ‘Amarelejo’ (PI270132), DT369, Kyle, Sceptre, and VIR51658 were inoculated to loose smut races T33, T26, T32, and a T33/T26 mix and seeded in the field and greenhouse. The disease reaction of the checks was used to determine the selection point within experimental lines. Five spikes were collected off different loose smut resistant plants in the spike row and bulked. The 97 F3 seed bulks were sent to the Brawley, CA, nursery for increase. Color and gluten strength were tested on seed harvested from remaining spikes from the field rows at Swift Current in fall 1991. Using the disease and other trait results of the F3 testing at Swift Current, 50 F4 lines representing 14 F1-derived families were selected from the winter nursery and grown in two replicate, randomized complete block design field tests near Swift Current and Regina, SK, in spring 1992. Each replication contained Sceptre, Plenty, Kyle, DT369, DT367, Medora, Wakooma, and DT618 as checks planted in four row plots as described above. Grain yield, relative maturity, relative height, lodging, and leaf spotting reaction were evaluated. Leaf rust and stem rust were evaluated in a rust-inoculated nursery near Winnipeg, MB. Whole grain protein concentration was measured on selected lines using near infrared reflectance (ICC, 1995). Within each Swift Current plot of replicate 1, a spike on two different plants was partial vacuum infiltration inoculated (Nielsen and Thomas, 1995) with the mixture of races T26, T32, and T33, and five uninoculated spikes were collected off different plants. All results were used to select 20 lines from seven families, which were grown as spike rows in the greenhouse (inoculated) or increased in spike rows at the winter nursery near Brawley, CA (uninoculated). Grain-quality evaluation (gluten strength and pigment content), loose smut testing, and agronomic trait selection within the Brawley nursery determined which F6 lines were retained.
Thirty lines representing four F1-derived families from the winter nursery seed increase were planted in replicated four-row plots near Swift Current and Regina in 1993 and evaluated for grain yield, relative height, relative maturity, lodging, and leaf spot reaction [leaf spot complex caused by Pyrenophora tritici-repentis (Died.) Drechs., Phaeosphaeria nodorum (E. Müller) Hedjaroude, Mycosphaerella graminicola (Fuckel) J. Schröt. in Cohn (anamorph Septoria tritici Roberge in Desmaz.), and/or Cochliobolus sativus (Ito & Kuribayashi) Drechs. ex Dast.]. Test design and traits evaluated were similar to the 1992 test with the addition in 1993 of Amarelejo as a check. Leaf rust (Puccinia triticina Eriks.) and stem rust (P. graminis Pers.:Pers. f. sp. tritici Eriks. & E. Henn.) ratings were obtained from a rust inoculated nursery near Winnipeg. A single 2.76-m2 four-row plot of each line was also planted at Swift Current for increase of seed for 1994 testing in the Durum Western A-test; three spikes of each line within this increase were partial vacuum inoculated with the three race mixture of loose smut. Two of the vacuum-inoculated F7 spikes from each line were grown in spike rows in the greenhouse in fall 1993 and rated for disease. Results of agronomic and disease testing were used to select lines for protein concentration and grain-quality testing. Results of quality testing were used to further select lines.
Line Evaluation
The loose smut resistant F7 line designated P9162-BJ08*B was evaluated in preregistration trials in 1994 near Swift Current, Stewart Valley, Regina, Saskatoon, and Elrose, SK (Clarke, 1995), and in 1995 at the same locations without Stewart Valley but with the addition of Portage and Glenlea, MB (Clarke, 1996). Under the designation DT676, P9162-BJ08*B was evaluated in the 1996 Durum Cooperative trial at Manitoba sites Brandon, Elgin, Morden, and Glenlea; Saskatchewan sites Indian Head, Elrose, Saskatoon, Regina, Swift Current, and Stewart Valley; an Alberta site at Lethbridge; and a site at Langdon, ND. Evaluations were made for agronomic performance (yield, actual height, actual maturity, straw strength [scale of 1–9, where 1 = straight and 9 = flat], grain volume weight, kernel size, disease resistance: loose smut, stem rust, leaf rust, leaf spot, root rot [Fusarium spp. and Cochliobolus sativus (Ito & Kuribayashi) Drechs. ex Dast.], common bunt [Tilletia laevis Kühn in Rabenh. and T. caries (DC.) Tul. & C. Tul.]) and quality (wheat protein content, semolina protein content, mixograph development time, wheat pigment content, semolina pigment content, wheat sedimentation volume, falling number, hard vitreous kernels, semolina gluten index, wheat ash, brightness, and purity). Traits evaluated varied over the 3 yr of testing. Disease testing was performed as described by Clarke et al. (2000). Seed composites were prepared from representative locations for grain quality analysis (AACC, 2000; PRRCG, 1997). The intensity of foliar symptoms scale (McFadden, 1991) was used to score leaf spotting.
In 1995 19 F7 plants of DT676 were grown in the greenhouse; spikes were needle inoculated to individual races of T26, T32, and T33 on each plant, except one that was inoculated to only T32 and T33. Spikes were labeled relative to the source plant. Spike rows were grown in the greenhouse and evaluated for loose smut. In 1996 two spikes on each of four F8 plants of DT676 were inoculated with race T26. Spike rows were grown in the greenhouse and evaluated in 1997. In 2006 two spikes on each of 10 F13 plants were inoculated with T26 and grown out. Sceptre was inoculated as a susceptible control in all inoculations. In 2003 and 2004, DT676 was grown in a two replicate randomized complete block design in the field near Swift Current and Regina with checks ‘AC Avonlea’ (PI 599033), ‘AC Navigator’ (PI 610666), Kyle, Medora, Sceptre, DT369, and ‘Strongfield’ (PI 641223). Yield, actual maturity (date from seeding to one-half of the plot mature), actual height, and straw strength, as well as grain volume weight and kernel size, were evaluated. The 2004 Regina location suffered frost damage; therefore only actual height and straw strength were evaluated. Three spikes off different plants in each plot in 2003 and replicate 1 in 2004 of the Swift Current tests were partial vacuum inoculated with a race mixture of T33, T26, and T32, and two of the spikes from each plot were grown out and rated in spike rows in the greenhouse.
Growing Conditions in Greenhouse and Growth Chambers
Crossing and loose smut inoculations were done in the growth room at 18 to 21°C, with a 16-h light 8-h dark photoperiod. Plants were grown in 1-L cartons, fertilized with 71.4 mmol L–1 total nitrogen, 7.0 mmol L–1 available phosphoric acid, and 10.6 mmol L–1 soluble potash solution once every 2 wk. Loose smut evaluation and some loose smut inoculations were conducted in the greenhouse under the same fertilization regime as the growth rooms and temperatures ranging from 14°C at night to 26°C during the day. Supplemental artificial lighting was provided during 16 h of the day.
Statistical Analyses
The 1994, 1995, and 1996 results over environments were analyzed to generate means and LSDs from a randomized complete block design where environments and replications were considered random and genotypes and year were fixed. The 2003 and 2004 means and LSDs were generated using the PROC MIXED procedure on a randomized complete block design where environments and replications were considered random and genotypes were fixed (SAS Institute, 1999). Mean differences were evaluated at the 0.05 significance level. Loose smut was calculated as percentage incidence where the number of plants with disease was divided by the total number of plants evaluated multiplied by 100. Standard errors of the mean loose smut incidence over replicates were calculated and are reported with the means as 
.
Characteristics
The 19 plants of DT676 inoculated in 1995 were completely resistant (0% incidence) to races T32 and T33 and exhibited a low level of infection to race T26 (Table 1 ). The susceptible check, Sceptre, produced high levels of infection, indicating good inoculum potential. In retests with race T26 in 1996 and 2006, DT676 continued to show low disease incidence, while the Sceptre check showed very high incidence. DT676 showed no to low infection to the three race mixture of loose smut in 3 yr of field testing with the partial vacuum infiltration method. Greater variability is associated with this method, but DT676 was consistently low relative to susceptible Sceptre.
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The coefficient of parentage of DT676 with Kyle was calculated at 0.81 using the International Crop Information System which uses the Sneller (1994) algorithm; the two lines are similar in many respects. Like Kyle and other durum cultivars (Plenty, AC Morse, AC Melita) registered for Western Canada, DT676 was resistant to stem rust, leaf rust, and common bunt between 1994 and 1996 (Table 2 ). A leaf spot reaction of DT676 fell within the range of the registered cultivars in 1995 and 1996 but was the highest reaction in 1994. The mean leaf spot ratings over two locations showed DT676 to be most similar to Kyle.
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Small quantities of seed (2 g) are available by contacting the corresponding author. Seed will be maintained by the Semiarid Prairie Agricultural Research Centre, AAFC, Swift Current. The germplasm may be used for research and breeding. A sample of the seed has been deposited into the USDA–ARS, National Plant Germplasm System. The source of the germplasm should be acknowledged when used in plant science research or breeding leading to publication or variety registration.
Acknowledgments
We gratefully acknowledge technical assistance of L.L. Thiessen, D. Green, M. Olfert, J. Ross, and R.A. Ferguson. Thanks to Dr. F. Clarke for review of the manuscript.
Footnotes
All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.
Received for publication June 15, 2007.
References
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