Breeding food barley : from agronomic assessment to marker assisted selection

Abstract

This research was undertaken to provide barley growers, processors, and consumers with quality food barley. Because all currently available varieties of food barley are of spring growth habit, the first phase of the research involved agronomic assessment of these varieties under Oregon conditions. Because winter barley usually yields more than spring barley in these environments, the second phase of this research involved development of winter habit food barley germplasm. Grain β-glucan content is the most important attribute for food barley varieties. This trait is important because of the cholesterol-reducing properties of β-glucan. Thirty three cultivars and advanced lines reported to vary in β-glucan content were grown in 2006 and 2007 at two locations in northeastern Oregon under dryland cropping conditions. Seed yield, test weight, percentage of plump kernels, grain β-glucan and grain protein were measured on replicated samples from the four environments. Hulled, waxy starch varieties appear to have the greatest agronomic potential for dryland production as they combine high yield potential and grain β-glucan percentage. Marker assisted selection was used to rapidly develop barley germplasm with novel combinations of alleles at loci controlling starch synthesis and growth habit. The target loci were WAX, VRN-H1, and VRN-H2. The goal was to develop waxy starch, high grain β-glucan, and winter habit germplasm. Pre-screening of candidate parental lines identified combinations with target vrn-H1 (winter) alleles. This allowed for immediate fixation of favorable alleles at this locus. VRN-H1 is coincident with a major low temperature tolerance QTL (Fr1). Perfect markers were based on functional domains in GBSSI and ZCCT-H, the genes determining wax and VRN-H2. Because spring growth habit at VRN-H2 is due to gene deletion, codominant alleles at a tightly linked locus (HvSNF2), were also used. Backcross-derived germplasm was genotyped in two stages. Homozygotes at the two loci were identified in one-step screening in the progeny of the double cross. BC1F3 and DCF3 lines were advanced to field testing in the Fall of 2007. In subsequent generations, these lines will allow for testing hypotheses regarding the pleiotropic effects of waxy starch on β-glucan and vernalization genes on low temperature tolerance.