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a USDA-ARS, 1301 N. Western Rd., Stillwater, OK 74075
b USDA-ARS, P.O. Box 307, Aberdeen, ID, 83210
* Corresponding author (Do.Mornhinweg{at}ars.usda.gov).
STARS 0620B (Reg. No. GP-144, PI 642906), STARS 0621B (Reg. No. GP-145, PI 642907), STARS 0622B (Reg. No. GP-146, PI 642908), STARS 0623B (Reg. No. GP-147, PI 642909), STARS 0624B (Reg. No. GP-148, PI 642910), STARS 0625B (Reg. No. GP-149, PI 642911), STARS 0626B (Reg. No. GP-150, PI 642912), STARS 0627B (Reg. No. GP-151, PI 642913), STARS 0628B (Reg. No. GP-152, PI 642914), STARS 0629B (Reg. No. GP-153, PI 642915), STARS 0630B (Reg. No. GP-154, PI 642916), STARS 0631B (Reg. No. GP-155, PI 642917), STARS 0632B (Reg. No. GP-156, PI 642918), STARS 0633B (Reg. No. GP-157, PI 642919), STARS 0634B (Reg. No. GP-158, PI 642920), STARS 0635B (Reg. No. GP-159, PI 642921), and STARS 0636B (Reg. No. GP-160, PI 642922) are spring, two-rowed barley (Hordeum vulgare L.) lines developed cooperatively by the USDA-ARS, in Stillwater, OK, and Aberdeen, ID, as sources of resistance to Russian wheat aphid (RWA) [Diuraphis noxia, (Mordvilko)]. Each line has a different source of resistance in one of four, two-rowed, malting barley cultivar backgrounds (Table 1 ).
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Devastating yield losses occurred in wheat (Triticum aestivum, L.) and barley in the western USA within the first 2 yr after the first appearance of the RWA in 1986 (Porter et al., 1999). Screening of the entire USDA-ARS National Small Grains Collection of H. vulgare in the greenhouse by the USDA-ARS in Stillwater, OK, resulted in the identification of 109 accessions with resistance to RWA ranging from resistant (1–3) to moderately resistant (4–5) on Webster's scale of 1 to 9 (1 = resistant, 9 = susceptible) (Webster et al., 1991) From these heterogeneous accessions, 109 homogeneous unadapted RWA-resistant germplasm lines were developed by selecting for RWA resistance as well as plant type. Two spring germplasm lines, STARS 9301B and STARS 9577B, were quickly released to breeders in 1993 and 1995, respectively (Mornhinweg et al., 1995, 1999). These lines, although highly resistant to RWA feeding damage, were not well adapted to U.S. feed or malting barley production environments. Breeder concerns about potential negative effects of unadapted germplasm on the agronomic performance and malting quality of elite breeding lines, led to the initiation of a backcross breeding program in Stillwater to develop RWA-resistant germplasm lines in backgrounds adapted to all barley-growing areas of the USA where RWA is a potential threat. All 109 unadapted resistant lines were used in the backcross breeding program. Seven RWA-resistant winter feed barley germplasm lines, in a ‘Schuyler’ (Jensen, 1972) background, were released in 2006 (Mornhinweg et al., 2006b). Simultaneous to this release of two-rowed spring germplasm lines, a set of 19 six-rowed, spring germplasm lines (Mornhinweg et al., 2007) and a set of 7 two-rowed spring feed barley germplasm lines are being released.
In the present germplasm release, all lines were the best agronomic performers in each of four two-rowed malting barley backgrounds, ‘B1202’, ‘Crest’ (Muir et al., 1992), ‘Crystal’ (Wesenberg et al., 1991), and ‘Harrington’. These lines are competitive with their recurrent parents in the field even in the absence of RWA (yields ranged from 86 to 108% of recurrent parent; Table 1).
Each germplasm line was developed with three backcrosses of an unadapted RWA-resistant germplasm line as the male to a two-rowed malting cultivar female parent (Table 1). Backcross progeny were screened in each generation (BC1 and BC2), and only resistant plants were used in the next backcross. Approximately 100 BC3F2:3 individuals from each cross were increased in the greenhouse. Seed from these plants were grown in the field as plant rows in Aberdeen, ID, and evaluated for agronomic performance in comparison to the susceptible recurrent parent. Selected lines were grown in replicated yield trials, in the absence of aphids, for 2 yr in Aberdeen, and one line from each resistant source was selected for release (Table 1). BC3F6 seed from each of these 17 lines was screened in the greenhouse in Stillwater for homozygous resistance to the RWA1 biotype. If seed was not homozygous for resistance, resistant plants were rescued, increased in the greenhouse, and screened for homozygosity. Homozygous resistant plants were then increased in the greenhouse/field, screened for homozygous resistance, and bulked for release. Promising lines were further evaluated in advanced yield trails at three locations in Idaho.
Genetic diversity for aphid resistance is very important due to a very real potential in aphids for the development of biotypes capable of damaging previously resistant lines. The resistant sources in STARS 0620B, 0621B, 0622B, 0626B, 0628B, 0632B, and 0635B were collected in Afghanistan, the resistant sources in STARS 0633B and 0634B were collected in the Russian Federation, and the resistant sources in STARS 0623B, 0624B, 0625B, 0627B, 0629B, 0630B, 0631B, and 0636B were collected in Turkmenistan, Syria, Germany, Iran, Egypt, France, Algeria, and the USA, respectively. Haley et al. (2004) reported a new biotype of RWA damaging to previously resistant wheat in Colorado. Thirteen of these STARS lines were resistant and four were moderately resistant to this new biotype in greenhouse seedling tests. Populations have been developed to determine the inheritance of resistance in each unadapted line represented in these germplasm lines as well as the genetic diversity for RWA resistance among these lines.
Seed of these germplasm lines will be deposited in the National Plant Germplasm System, where they 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 these germplasm lines contribute to research or the development of an improved line, cultivar, or hybrid. Seed of resistant STARS lines will be distributed on request to breeders and geneticists in lots of 5 g. Requests for seed should be sent to the corresponding author.
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 December 19, 2006.
References
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