Registration of Seven Winter Feed Barley Germplasms Resistant to Russian Wheat Aphid

STARS 0501B (Reg. no. GP-137, PI 639870), 0502B (Reg. no. GP-138, PI 639871), 0503B (Reg. no. GP-139, PI 639872), 0504B (Reg. no. GP-140, PI 639873), 0505B (Reg. no. GP-141, PI 639874), 0506B Reg. no. GP-142, (PI 639875), and 0507B (Reg. no. GP-143, PI 639876), are winter, six-rowed feed barley (Hordeum vulgare L.) lines developed cooperatively by the USDA-ARS at Stillwater, OK, andAberdeen, ID, as sources of resistance to Russian wheat aphid (RWA) [Diuraphis noxia (Mordvilko)]. Although these lines were selected for adaptation to southeastern Idaho, sister lines have been shown to be adapted as far south as central Colorado. Each line has a different source of resistance in the ‘Schuyler’ (Jensen, 1972)winter feed barley background (Table 1). These germplasm lines are highly resistant to theRWAwhen seedlings are tested in the greenhouse with greenhouse-reared RWA colonies (Table 1). Greenhouse seedling screening resistance ratings have been shown to accurately predict field resistance (Mornhinweg et al., 2006). The major component of resistance in these lines is tolerance. Even while supporting high RWA populations, leaves of these germplasm lines do not roll or streak in response to RWA and therefore yield reductions due to head trapping and chlorosis of susceptible cultivars does not occur in these lines (Mornhinweg et al., 2006). Devastating yield losses occurred inwheat (Triticumaestivum, L.) and barley in the western USAwithin the first 2 yr after the introduction of the RWA in 1986 (Porter et al., 1999). Screening of the entire USDA-ARS National Small Grains Collection of Hordeum vulgare in the greenhouse by the USDA-ARS at 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 5 resistant, 9 5 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 (Mornhinweg et al., 1995, 1999). These lines, though highly resistant to RWA feeding damage, were not well adapted to U.S. feed or malting barley production. Breeder concerns about potential negative effects of unadapted germplasm on the agronomic performance and malting quality of elite breeding lines, lead to the initiation of a backcross-breeding program at Stillwater to develop RWA-resistant germplasm lines in backgrounds adapted to all barley-growing areas of the USAwhere RWA is a potential threat. All 109 unadapted resistant lines were utilized in the backcross breeding program. STARS 0501B, 0502B, 0503B, 0504B, 0505B, 0506B, and 05017B were the seven best agronomic performers in a Schuyler background.These lines are very competitive with Schuyler in the field even in the absence of RWA. STARS 0501B, STARS 0502B, STARS 0503B, STARS 0504B, STARS 0505B, STARS 0506B, and STARS 0507B had grain yields 100, 99, 106, 113, 107, 102, and 102%, respectively, of their recurrent parent Schuyler. Test weights were 100, 102, 100, 98, 100, 100, and 99%, respectively, of Schuyler test weight and plant heights were 106, 106, 97, 94, 97, 97, and 100%, respectively, of Schuyler plant height. STARS 0501B, STARS 0502B, STARS 0503B, STARS 0504B, STARS 0505B, STARS 0506B, and STARS 0507B were12, 0, 12, 0, 12, 11, and 12 d different, respectively, in heading than Schuyler. Each of these germplasm lines was developed with three backcrosses to Schuyler (female parent) using a single unadapted RWA-resistant winter barley germplasm line (Table 1). Backcross progeny were screened in each generation (BC1 and BC2) and only resistant plants were used in the next backcross. Eventually, 100 BC3F2:F3 individuals were increased in the greenhouse. Seed from these plants were grown in the field as plant rows at Aberdeen, ID, and evaluated for agronomic performance in comparison to the susceptible parent Schuyler. Selected lines were grown in replicated yield trials, in the absence of aphids, for 2 yr (2002 and 2003) at Aberdeen, ID, and one line from each resistant source was selected for release (Table 1). Three hundred spikes were selected from each of these seven lines and screened in the greenhouse at Stillwater for homozygous resistance to the RWA1 biotype. Remnant seed from homozygous resistant plants were bulked for each line. Genetic diversity for aphid resistance is very important due to the very real potential in aphids for the development of biotypes capable of damaging previously resistant lines. The source of resistance in STARS 0503B (Table 1) was collected in Afghanistan while the resistant sources in STARS 0501B, 0502B, 0504B, 0505B, 0506B, and 05017B were collected in Iran. Haley et al. (2004) reported a new biotype of RWA damaging to previously resistant wheat in Colorado. STARS 0501B, 0502B, 0503B, 0504B, 0505B, 0506B, and 05017B were 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 STARS 0501B, 0502B, 0503B, 0504B, 0505B, 0506B, and 0507B will be distributed on request to breeders and geneticists in lots of 5 g. Requests for seed should be sent to the corresponding author. 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 these germplasm lines will be deposited in the National Plant Germplasm System where they will be available after 5 yr for research purposes, including development and commercialization of new materials.