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Associations Between Vrs1 Alleles and Grain Quality Traits in Spring Barley Hordeum vulgare L.¹

¹This research was supported by USDA-ARS National Research Initiative Competitive Grants Program grants 2004-35301-14538 and 2007-35301-18135; Montana Board of Research and Commercialization Technology; and Montana Agricultural Experiment Station. ²Department of Plant Sciences and Plant Pathology, Montana State University, 119 Plant Bioscience Building, Bozeman, MT 59717-3150. ³Department of Animal and Range Sciences, Montana State University, Bozeman, MT 59717-2900. ⁴USDA-ARS, Wheat Quality Laboratory, P.O. Box 646394, E-202 Food Quality Building, Washington State University, Pullman, WA 99164-6394. ⁵Corresponding author. Phone: (406) 994-7877. Fax: (406) 994-7600. E-mail: mgiroux@montana.edu

Barley head row type is a major trait affecting end-use quality. Six-rowed forms emerged due to mutations in the Vrs1 gene in two-rowed barleys. Whether barley is two (Vrs1) or six rowed (vrs1) directly affects a wide range of morphological traits related to seed yield and grain quality. Vrs1 has been cloned and encodes a homeodomain transcription factor with a linked leucine zipper motif. To test the association between Vrs1 alleles and grain quality, we characterized the Vrs1 alleles among a well-described collection of 81 spring barley accessions selected for divergence in head type and dry matter digestibility (DMD). The results indicated that the majority of two-rowed barleys have the Vrs1.b3-1 allele and the majority of six-rowed barleys carry the vrs1.a1-8 allele. In comparison with two-rowed barleys, six-rowed barleys were more variable in grain hardness. This divergence in hardness values was associated with specific vrs1 alleles, with barley accessions carrying the less severe amino acid missense mutation VRS1.a3-1 isoform being softer and having higher DMD than those accessions carrying the more common VRS1.a1-1 amino acid frameshift isoform. The assignment of six-rowed barley cultivars to different vrs1 allele groups may prove beneficial for the selection of specific grain-quality parameters.