The inheritance of extreme earliness for heading time, as measured by days to awn appearance (DAA), in ‘Super Precoz (2H)’ (SP), a photoperiod‐insensitive spring barley (Hordeum vulgare L.), was investigated in field studies under short daylengths at Davis, CA, and Ciudad Obregón, Sonora, Mexico, to obtain additional information on gene action. The DAA data from parental, F1, F2, F3, and F4 generations indicated that extreme earliness in SP was conferred by a single locus when homozygous recessive. Data from 75 F3 families evaluated for DAA in a field study and by starch gel electrophoresis of seedling‐plumule extracts indicated that the locus conferring extreme earliness was linked to Est 1 and Est 3 on the long arm of Chromosome 3 with ≈2% recombination. The locus was assigned gene symbol Easp. The dominant allele Easp suppressed the recessive allele easp and permitted the expression of other unidentified Ea loci conferring relative lateness. Allelism tests indicated recessive epistatic interactions between the Easp locus and the Eak and Ea7 loci. The easp recessive homozygote suppressed numerous other Ea maturity loci and headed earlier than the other three recessive homozygotes (i.e., eak, ea7, or eac), which were phenotypically similar.

Malting quality data were collected on malts from three barley (Hordeum vulgare L.) breeding program trials. We tried to identify causal polymorphisms in the Bmy1 intron III and coding regions for use in marker‐assisted selection. Abundant malting quality variation exists in the spring barley germplasm despite the parents having identical Bmy1 intron III and coding regions. After complete Bmy1 sequencing, no polymorphisms associated with malting quality phenotypes, indicating the genetic basis for the observed variation resides outside Bmy1. Complete allele sequencing identified one winter barley parent that had a novel Bmy1 allele (Sd1a) based on amino acid substitutions that are candidates as causative agents for the phenotypic variation. Marker‐assisted selection against the Sd1a allele could be effective in improving diastatic power (DP). The Sd1a allele is associated with low DP and is present in only three of the 51 lines, presumably due to preceding generations being selected for high DP. Selection for DP has subsequently eliminated the Sd1a allele from this breeding program. This research shows the importance of having complete allele sequences and knowledge of functional polymorphisms in target genes before using marker‐assisted selection.

California has a vibrant and growing craft brewing industry and a nascent malting industry interested in locally sourced products, which has created a demand for malting barley (Hordeum vulgare L.) production in California. ‘UC Tahoe’ (Reg. No. CV‐365, PI 678971) is the first malting barley cultivar released by the University of California and is well adapted to California's Central Valley (Sacramento and San Joaquin Valleys). UC Tahoe is a two‐rowed spring barley with good resistance to powdery mildew and tolerance to yellow dwarf viruses. UC Tahoe combines four quantitative trait loci for resistance to Cereal yellow dwarf virus (CYDV) that were previously identified in the cross between ‘Butta 12’ and ‘Madre Selva’. While not currently a cultivar approved by the American Malting Barley Association, UC Tahoe meets the quality needs of a craft malting and brewing industry interested in sourcing locally grown barley.

Two high‐yielding, short‐statured spring wheats (Triticum aestivum L.), ‘Anza’ and ‘UC 44‐111,’ differ in certain characteristics of N metabolism. Nitrate reductase activity (NRA), measured in vitro on shoots or lamina of seedling plants, was about 8 and 18 µmoles of nitriteproduced/hour/g fresh weight for Anza and UC 44‐111, respectively. The genetic basis for this difference was investigated with an in vitro NRA assay on seedling plants to determine the NRA frequency distributions of parents, F1, F2, reciprocal BCF2 and randomly derived F6 lines. All data were consistent in showing that UC 44‐111 has a single dominant gene (Nra) which accounted for most of the variability observed for NRA.

Cereal yellow dwarf virus (CYDV-RPV) causes a serious viral disease affecting small grain crops around the world. In the United States, it frequently is present in California where it causes significant yield losses, and when infections start early in development, plant death. CYDV is transmitted by aphids, and it has been a major impediment to developing malting barley in California. To identify chromosome locations associated with tolerance/resistance to CYDV, a segregating population of 184 recombinant inbred lines (RIL) from a cross of the California-adapted malting barley line Butta 12 with the CYDVtolerant Madre Selva was used to construct a genetic map including 180 polymorphic markers mapping to 170 unique loci. Tolerance to CYDV was evaluated in replicated experiments where plants were challenged by aphid mediated inoculation with the isolate CYDV-RPV in a controlled environment. Quantitative trait loci (QTL) analysis revealed the presence of two major QTL for CYDV tolerance from Madre Selva on chromosomes 2H (Qcyd.MaBu-1) and 7H (Qcyd.MaBu-2), and 4 minor QTL from Butta 12 on chromosomes 3H, 4H, and 2H. This paper discusses the contribution of each QTL and its potential value to improve barley tolerance to CYDV.