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Eastern Cereal and Oilseed Research Center, Agriculture and Agri-Food Canada, 960 Carlling Ave., Ottawa, ON Canada K1A 0C6
* Corresponding author (fedakga{at}agr.gc.ca).
ABSTRACT
TC 67 red spring wheat (Triticum aestivum L.) (Reg. No. GP-856, PI 654367) was developed at the Cereal and Oilseed Research Center, Agriculture and Agri-Food Canada. TC 67 was derived from the cross Crocus*2/PI343447 (T. timopheevii Zhuk). A segregating population of 1500 BC1F2 plants was established and advanced to F7, using single seed descent. One hundred lines were selected from 535 BC1F7 lines, on the basis of plant fertility and agronomic traits, and evaluated for reaction to Fusarium head blight (FHB; caused by Fusarium graminearum) for two seasons. TC 67 had high levels of resistance to FHB that was comparable to that of ‘Sumai 3’, the most FHB resistant wheat available, based on point inoculation. The resistance of TC 67 to FHB was further evaluated in replicated field trials, compared with two resistant wheat lines, Sumai 3 and ‘HY 644’, in a FHB disease nursery in 2003 and 2004. The results show that TC 67 was significantly better than HY 644 in FHB incidence, severity, and Fusarium-damaged kernels and was comparable to Sumai 3 in deoxynivalenol content in the grain.
Abbreviations: DON, deoxynivalenol • FHB, Fusarium head blight • SSD, single seed descent
Fusarium head blight (FHB), caused by Fusarium graminearum, is a highly destructive disease of spring wheat (Triticum aestivum L.). Epidemics of the disease can result in significant economic losses in terms of reducing yield and degrading quality. Development of resistant cultivars is an effective means of controlling the disease. However, sources of resistance to FHB are limited to a few wheat cultivars, such as ‘Sumai 3’ (Anderson et al., 2001) and ‘Frontana’ (Steiner et al., 2004), which hinders the development of improved cultivars with resistance to FHB. Therefore, new sources of resistance must be identified and exploited. Several wild species were identified with a high level of resistance to FHB, such as Leymus racemosus (Elymus gigantus L.), Roegneria kamoji and Roegneria ciliaris (Chen et al., 2004) and several Aegilops species (Fedak et al., 2003). Several translocation lines that are resistant to FHB have been developed (Chen et al., 2004). However, these lines need to be improved for agronomic traits before they are used in a wheat breeding program because of linkage drag. Triticum timopheevii, a relative of bread wheat with the genomic constitution of AAGG, is known for its resistance to many diseases, such as common root rot [Cochliobolus sativus (Ito &Kuribayashi) Drechs. Ex Dastur] (Bailey et al., 1993), stem rust (Puccinia graminis Pers. f. sp. tritici Eriks. & E. Henn.) (Allard and Shands, 1954), leaf rust (P. tritici Eriks) (Leonova et al., 2007), powdery mildew [Blumeria graminis (DC.) E.O. Speer f. sp. tritici Em. Marchal] (Jorgensen and Jensen, 1972), and Septoria nodorum blotch [Stagonospora nodorum (Berk.) Castellani & E.G. Germano] (Ma and Hughes, 1995). An accession of T. timopheevii Zhuk, PI 343447, has been found to have a high level of resistance to Fusarium head blight. This report describes the production and FHB resistance of T. timopheevii–derived wheat lines.
Methods
Early Generation Development
Crocus (PI 606243), a spring wheat, was crossed to T. timopheevii Zhuk, PI 343447, as the pollen parent, in the greenhouse in 1999. Crocus, provided by G. Scoles, University of Saskatchewan, is susceptible to FHB. This line has three crossability genes Kr1, Kr2, and Kr3 derived from Chinese Spring with the genetic background of ‘Columbus’ (Zale and Scoles, 1999). Spikes of Crocus were emasculated and sprayed with 2, 4–D (100 mg L–1) at 24 h after pollination. The F1 plants were backcrossed with Crocus, and embryo rescue techniques were used for establishing the hybrids of both the cross and the backcross. Following a backcross with Crocus, a population of 1500 F2 plants was established and 535 BC1 F7 lines were developed in the greenhouse, using single seed descent (SSD). One hundred lines were selected on the basis of plant fertility and agronomic traits and were evaluated for reaction to FHB in the greenhouse and field FHB nursery with four replications for two growing seasons. From this population, the line TC 67 (Reg. No. GP-856, PI 654367) was selected, on the basis of its superior FHB reaction and reasonable agronomic traits.
Disease Evaluation with Point Inoculation in the Greenhouse
Wheat plants for FHB evaluation were grown in the greenhouse with temperatures of 20°C during the day and 15°C at night. During the flowering stage, a floret in the middle spikelet was injected with 10 µL of inoculum. The inoculum was a suspension of 50,000 spores mL–1 of three aggressive isolates of F. graminearum. The inoculated plants were misted for 48 h in a misting room at 25°C. Symptoms were rated 21 d after inoculation.
Disease Evaluation in the FHB Nursery
One FHB resistant line, TC 67, was further evaluated for FHB reaction in a four-replicate field FHB nursery in 2003 and 2004. Each experimental plot consisted of two rows, 1 m long spaced 30 cm apart. The nurseries were inoculated twice each year with corn (Zea mays L.) and barley (Hordeum vulgare L.) kernels that were autoclaved and inoculated with three isolates of F. graminearum. The infected kernels were spread in the FHB nurseries at 100 g m–2. The first inoculation was at the tillering stage, and the second inoculation was made 10 d later. The FHB nurseries were irrigated twice each day (morning and afternoon) during the interval between the first inoculation and the soft dough stage. Cultivars Sumai 3, Roblin, and HY 644 were included as highly tolerant, susceptible, and partially tolerant checks, respectively.
Deoxynivalenol Analysis
Samples of wheat were analyzed by ELISA using a monoclonal antibody (Sinha and Savard, 1997). A 1.0-g sample of ground wheat was extracted with 5 mL of 9:1 water/methanol for 1 h. The samples were then centrifuged and a portion of the extract withdrawn. The extracts were mixed with a solution of deoxynivalenol (DON)–horseradish peroxidase conjugate, and the resulting solutions were added to a 96-well plate precoated with DON antibodies. After 30 min, the plate was washed eight times with PBST, and the amount of bound peroxidase was determined by reaction with o-phenylenediamine in the presence of hydrogen peroxide. After 30 min, the reaction was stopped by addition of HCl; the intensity of the resulting color was measured at 490 nm and DON concentration was estimated from a standardized curve.
Characteristics
The greenhouse evaluation showed that TC 67 has a high level of resistance to FHB; only one spikelet was infected at 21 d after point inoculation. In the field nursery, the FHB incidence and severity and DON content of TC 67 were significantly lower than those of the partially resistant check HY 644 and comparable to those of Sumai 3, a worldwide-known resistant source (Table 1 ). Kernel appearance showed that TC 67 displayed a lower frequency of Fusarium-damaged kernels compared with the partially resistant check HY 644. TC 67 is also resistant to Stagonospora nodorum of wheat at the seedling stage (data not shown).
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Sumai 3 is a well-known source for resistance to FHB. The major resistant gene is located on chromosome 3BS (Anderson et al., 2001). TC 67 is comparable to Sumai 3 for FHB resistance based on symptoms and DON levels. The resistant gene(s) for resistance to FHB of TC 67 (derived from T. timopheevii) has not been identified. This line has been crossed with AC Brio, a susceptible genotype, and an F6 population of 235 lines has been developed through SSD. Currently, these lines are being phenotyped for FHB reaction in the greenhouse to map its resistance to FHB. Once the FHB resistance gene(s) from TC 67 have been characterized and mapped, it may be possible to pyramid them with Fhb1 from Sumai 3.
Availability
Small quantities of seed to be used for research or breeding purposes can be requested from the corresponding author. Requests for small quantities of seed can also be made via the Germplasm Resources Information Network website (http://www.ars-grin.gov/npgs).
Acknowledgments
The spring wheat line Crocus was kindly provided by Dr. Graham Scoles, Dep. of Plant Sciences, University of Saskatchewan, Canada.
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 August 6, 2008.
References
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