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a USDA-ARS, 1301 N. Western, Stillwater, OK 74075
b USDA-ARS, National Small Grains Germplasm Research Facility, 1691 S. 2700 W., Aberdeen, ID 83210
c Dep. of Plant and Soil Sciences, 368 Ag Hall, Oklahoma State Univ., Stillwater, OK 74078
d Dep. of Bioagricultural Sciences and Pest Management, 1177 Campus Delivery, Colorado State Univ., Ft. Collins, CO 80523
e Texas A&M Univ., College Station, TX
f University of Nebraska Panhandle Research and Extension Center, Scottsbluff, NE 69361
* Corresponding author (Do.Mornhinweg{at}ars.usda.gov).
ABSTRACT
‘Sidney’ (Reg. No. CV-344, PI 641939), a Russian wheat aphid [RWA, Diuraphis noxia (Kurdjumov)]–resistant, spring, two-rowed, feed barley (Hordeum vulgare L.) tested as 98BX 44B, was developed and released by the USDA–ARS, Stillwater, OK, and Aberdeen, ID; Colorado State University; and the University of Nebraska. Introduction of RWA to the United States effectively eliminated spring barley, the preferred alternate crop, in winter wheat (Triticum aestivum L.) rotations, in eastern Colorado and western Nebraska. ‘Otis’, a spring barley well adapted to the high dry plains, is susceptible to RWA. STARS 9301B, the first RWA-resistant barley germplasm line released in the United States, has a high level of resistance to the aphid. With RWA resistance from STARS 9301B transferred to Otis through backcross breeding, Sidney outperforms Otis in this marginal production area.
Abbreviations: QTL, quantitative trait locus • RWA, Russian wheat aphid
‘Sidney’ (Reg. No. CV-344, PI 641939) a Russian wheat aphid [RWA, Diuraphis noxia (Kurdjumov)]–resistant, spring, two-rowed, feed barley (Hordeum vulgare L.) tested as 98BX 44B, was developed and jointly released by the USDA–ARS, Stillwater, OK; USDA–ARS, Aberdeen, ID; Colorado State University; and the University of Nebraska. Since 1986, RWA has been a persistent pest of small grains in eastern Colorado, western Nebraska and Kansas, and southeastern Wyoming. The hot dry plains in these areas are marginal small grains dryland production areas where crop rotations are necessary for moisture conservation as well as reduction of soil erosion. Until the introduction of the RWA in 1986, feed barley was successful as the alternate crop in winter wheat (Triticum aestivum L.) rotations and valued as an irrigated feed crop. All barley cultivars that were available in the 1980s are susceptible to RWA. Russian wheat aphid prevents newly emerging leaves from unrolling, resulting in head entrapment and yield loss, and protecting the aphids from contact insecticides. Under heavy infestations, effective control requires multiple applications of systemic insecticides which are environmentally undesirable and economically prohibitive in these marginal dryland production areas. For the growing seasons of 1984 to 1986, an average of 62,700 ha of barley was planted in 16 eastern Colorado counties with gross sales of $14 million. In 2004, only 280 ha were planted and the average gross sales from the same counties from 1994 to 2004 was only $750,000 annually (Bosley, 2006). Our breeding objective was to develop a RWA-resistant feed barley suited to production in eastern Colorado, western Nebraska and Kansas, and southeastern Wyoming.
Sidney has the pedigree ‘Otis’*4/STARS 9301B. Otis (PI 8775) was selected from the cross ‘Munsing’ (CI 6009)/‘Spartan’ (CI 5027). Otis was developed specifically for the high dry plains and released by Colorado State University in 1951 (Robertson, 1965) as an early-maturing, spring feed barley with high test weight and excellent yields under dryland conditions. The preferred alternate crop in winter wheat rotations for many years in Colorado, Otis is highly susceptible to RWA. STARS 9301B (PI 573080) was the first RWA-resistant spring barley germplasm line developed in the United States (Mornhinweg et al., 1995b). STARS 9301B is a highly RWA resistant selection from PI 366450, an accession collected in Afghanistan.
Methods
Sidney was developed via a modified backcross breeding procedure in which each BCxF1 progeny population was screened for RWA resistance. Successive backcrosses were made with resistant BCxF1 plants. Resistance screening was conducted as described by Webster et al. (1991) and BCxF1 plants were selected with resistance ratings of 2 on Webster's scale of 1 to 9 where a rating of 1 to 3 is resistant, 4 to 6 is moderately resistant to moderately susceptible, and 7 to 9 is susceptible (Webster et al., 1991). BC3F1 were increased to BC3F2 and screened in the greenhouse for RWA resistance. Approximately 130 resistant BC3F2 were increased in the greenhouse and resultant BC3F2:3 planted as plant rows in the field in Aberdeen, ID, in spring 2000 for agronomic evaluation and Breeder seed increase. Remnant seed from each BC3F2:3 was screened in the greenhouse as above and homozygous resistant lines were identified.
Selected resistant lines, Otis, and Otis treated with Gaucho (Otis + Gaucho) insecticidal seed treatment (Imidacloprid, Bayer Agricultural Products, Kansas City, MO), which controls early-season RWA infestations, were evaluated in replicated yield trials in 2001 through 2004 at 12 location-years in eastern Colorado and western Nebraska (Table 1 ). Plot size was 152 by 914 cm with 30.5-cm row spacing and a seeding rate of 70 kg ha–1. The RWA-resistant cultivar Burton (Bregitzer et al., 2005) and RWA-susceptible cultivar Baronesse (developed by Nordsaat in Germany and marketed in the United States by Westbred, LLC, Bozeman, MT) were also tested at one location in 2002 and four locations in 2004. These are truly dryland areas where 30-yr (1971–2000) average annual rainfalls are 40.23 cm (15.84 inches) in eastern Colorado and 40.00 cm (15.75 inches) in western Nebraska (High Plains Climate Center, http://www.hprcc.unl.edu/data/historical/ [verified 17 July 2009]). An extreme range of environments were encountered in this 4-yr testing period (Table 1). Rainfall ranged from 22.8 cm (9 inches) to 5.08 cm (2 inches) in January through June where annual average precipitation for those months is 20.3 to 22.86 cm (8–9 inches). Days from May through June with temperatures over 32°C (90°F) ranged from 1 to 21. Three locations were hailed out and one location-year was so dry the crop did not establish. Some locations were artificially infested with RWA by laying infested leaves in the plots. Other locations were either naturally infested (very lightly so) or aphid free (Table 1). Data collected included heading date (date of head emergence from the boot for 50% of plants), plant height, grain yield, test weight, percentage plump kernels (defined as the percentage of kernels retained on a sieve with 19.1- by 2.38-mm rectangular openings, Method Barley 2C: Assortment test; American Society of Brewing Chemists 1992), and aphid number per 20 tillers. Data were analyzed by a general analysis of variance via Statistix 9 (Analytical Software, Tallahassee, FL) and pairwise mean comparisons made using Tukey's HSD with p < 0.05. Data from locations with light natural infestations were pooled with data with no infestation in analyses because the light infestations were considered to have negligible affects.
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Characteristics
Sidney is a hulled, RWA-resistant, spring, two-rowed, feed barley with lax, midlong to long spikes that nod slightly at maturity. Spikes do not always emerge from the boot under severe drought conditions. Lateral glumes are reduced, and rachis edges have many long hairs. Lemma awns are long and smooth, while glume awns are rough and equal to the length of the glume. Glumes are covered with long hairs. Rachilla hairs are long, and the crease is V-shaped. Hulls are semiwrinkled with moderately predominate lateral veins. Lateral veins have few teeth, while marginal veins have none. Kernels are medium in size, plump, and symmetrical with a depression that tends to crease at the base. The aleurone is white. Sidney has the same maturity as Otis.
Sidney has a RWA resistance rating of 2 on Webster's scale of 1 to 9 (Webster et al., 1991). Russian wheat aphid resistance in donor parent STARS 9301B was determined to be controlled by one incompletely dominant gene, Rdn1, and one dominant gene, Rdn2, with recessive epistasis of Rdn2 on Rdn1 (Mornhinweg et al., 1995a). This source of resistance has been shown to provide significant protection against loss of agronomic performance (Mornhinweg et al., 2006; Bregitzer et al., 2003). Two major quantitative trait loci (QTLs) for RWA resistance in STARS 9301B have been mapped to chromosomes 1H and 3H with one minor QTL on 2H (Mittal et al., 2008). The QTL on 1H showed dominance and is likely Rdn2 while the QTL on 3H showed additive effects and is likely Rdn1. There was no evidence of epistasis in the QTL analysis, and it was suggested that the third QTL could be responsible for the original hypothesis of epistasis among Rdn1 and Rdn2. The comparable level of resistance in Sidney and STARS 9301B suggests all QTLs are present in Sidney. The major component of resistance in STARS 9301B is tolerance with antibiosis as a secondary mechanism (Webster et al., 1991). Leaves of Sidney do not roll or streak under RWA infestation. Although selected for resistance to RWA1, STARS 9301B has been reported to be resistant to five (RWA1-RWA5) of the eight RWA biotypes reported on wheat (Puterka et al., 2006). Sidney, with resistance from STARS 9301B, has been reported to have resistance to RWA6-RWA8 (Weiland et al., 2008).
Analysis of variance over all location-years for Sidney, Otis, and Otis + Gaucho indicated a significant location effect for all traits and a significant cultivar and cultivar x location effect for all traits except RWA number (Table 2 ). Cultivar x location interaction was not significant for any trait, including aphid number, when analysis included only the four infested location-years and not significant for plant height and grain yield when only the seven no or naturally light infested location-years were analyzed.
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Availability
Seed of Sidney was deposited in the National Plant Germplasm System, where it will be available for research purposes, including development and commercialization of new materials. It is requested that appropriate recognition of the source be given when this cultivar contributes to research or development of new breeding lines or cultivars. Seed of Sidney will be distributed on request to breeders and geneticists in lots of 5 g. Requests for seed should be sent to the corresponding author. Parties interested in commercial production of Sidney can obtain seed from Colorado Agronomy Foundation Seeds, Dep. of Soil and Crop Sciences, Colorado State University, Ft. Collins, CO, 80523, or Nebraska Foundation Seed Division, 1071 County Road G, Room C, Ithaca, NE, 68033-2234.
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 April 15, 2009.
References
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