It has been documenfed fhaf the dwarfing genes, Rht-Blb and Rht-Dlb, can reduce wheat {Triticum aestivum L.) coleoptile length (CL), buf their effects on number of roofs (RN) and roof length (RL) have nof been determined. Our objectives were to identify quanfitative trait loci (QTL) controlling CL, RN, and RL and to determine if any of fhe QTL correspond to wfieat dwarfing genes. A population consisting of 159 recombinanf inbred lines (RILs) was derived from tbe cross of Rio Blanco {Rht-Blb, Rht-Dla), a semidwarf cultivar with short CL, and IDQ444 {Rht-Bla, Rht-Dla), a tall germplasm wifh long CL. The CL, RN, longest root length (LRL), and total root length (TRL) were evaluated at two temperature regimes (18 and 22°C). A major QTL mapped to the Rht-Bl locus on chromosome 4B explained 64% of the phenotypic variation for CL, 9% for LRL, 26% for TRL, and 14% for plant height. The CL of fhe semidwarf RILs was significanfly less than that of the tall lines wfiile the reverse results were observed for LRL and TRL. Qur results indicated that the Rht-Bl gene had the pleiotropic effect of decreasing CL while increasing LRL and TRL. None of the six QTL for RN were mapped to the regions containing the Rht-Bl locus although semidwarf RILs had more roots than the tall lines. This study suggested that selection of the Rht-Blb alíele tended to increase root biomass, perhaps ameliorating its negative effect of reduced CL.

There is a lack of studies that have investigated grain yield, its components and photosynthesis in late stages of wheat growth, giving us insufficient understanding of how these factors interact to contribute to yield during this period. As a result, three field experiments were carried out examining 20 winter wheat genotypes of diverse origins under irrigated, terminal drought and dryland conditions in the southern Idaho. Our objective was to evaluate the interaction between post-anthesis physiological traits, especially leaf-level photosynthetic capacity, senescence and yield components on grain yield in different moisture regimes. Genotype differences were found in leaf-level photosynthesis and senescence, canopy temperature depression, grain yield and yield components in each water regime. Grain yield was closely associated with traits related to grain numbers. In all three moisture regimes, positive correlations were observed between grain yield and photosynthesis that were dependent on the timing or physiological growth stage of the photosynthetic measurement: highly significant correlations were found in the mid-and late grain filling stages, but no correlations at anthesis. Consistent with these findings, flag leaf senescence at the late grain filling stage was negatively correlated with grain yield and photosynthetic rate (under terminal drought and dryland conditions). These findings provided evidence that grain yield was sink-limited until the final stages of growth, at which time sustained photosynthesis and delayed senescence were critical in filling grain. Because the trends were consistent in moisture sufficient and deficient conditions, the results suggest that late-season photosynthesis and delayed leaf senescence are driven by the size of the reproductive carbon sink, which was largely governed by factors affecting grain numbers.

The primary trait in wheat (Triticum aestivum L.) to prevent damage caused by the wheat stem sawfly (WSS) (Cephus cinctus) is antibiosis facilitated by solid stems. The pith of solid stems impedes development of larvae, often resulting in their death inside the stem. A key question regarding solid stems is the possible impact on grain yield potential due to photosynthate partitioning to stem pith instead of to grain. Molecular markers for the major gene controlling stem solidness, Qss.msub‐3BL, were used to develop near‐isogenic lines (NIL) for alleles at Qss.msub‐3BL in six genetic backgrounds. The NIL were grown in replicated trials in 12 locations that varied for yield potential in Montana, Washington, and Idaho. There was no significant impact of the solid stem allele on grain yield based on mean performance over recurrent parents and locations. Individually, solid‐stemmed NIL were significantly lower yielding in one of six genetic backgrounds. Based on means over all crosses, the solid‐stemmed NIL had lower yield in only one high‐yielding environment. These results suggest that in general the allele for solid stems at Qss.msub‐3BL does not result in yield reduction. Development of solid‐stemmed cultivars with yield potential similar to the best hollow‐stemmed cultivars is a reasonable goal for wheat breeding programs in areas impacted by the WSS.

No abstract

‘UI Platinum’ (Reg. No. CV‐1112, PI 672533) hard white spring wheat (Triticum aestivum L.) was developed by the Idaho Agricultural Experiment Station and released in 2014. UI Platinum was derived from the cross ‘Blanca Grande’ × ‘Jerome’ and tested under experimental numbers A01178S, IDO694, and IDO694C. UI Platinum was released for its improved grain yield and desirable bread and whole grain end‐use quality in irrigated and high rainfall production areas. Grain yield, end‐use quality, and resistance to stripe rust (caused by Puccinia striiformis Westend f. sp. tritici) of UI Platinum are better or equivalent to the three widely grown hard white spring cultivars ‘SnowCrest’, ‘WB Idamax’, and ‘WB Paloma’. UI Platinum is also 1 to 2 d earlier and 2 to 3 cm shorter than WB Idamax and WB Paloma. The University of Idaho Agricultural Experiment Station will maintain breeder and foundation seed of UI Platinum. This cultivar is protected under the US Plant Variety Protection Title V and all seed requests should be sent to the inventor/breeder during the period of protection. Registered and certified seed production and sales will be handled by LimaGrain Cereal Seeds and Lansing Trade Group LLC.