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Hard red spring wheat (Triticum aestivum L.) grown in rainfed environments in the northern Great Plains of North America frequently encounter drought and heat stress during grain‐fill, thus reducing yield. Delayed leaf senescence after heading, known as the stay‐green trait, has been found to help spring wheat tolerate drought and heat stress during grain‐fill. To better understand how the stay‐green trait relates to expression of other agronomic traits, data was analyzed from a recombinant inbred line (RIL) population derived from a 'Vida'/MTHW0202 cross grown in rainfed and irrigated environments. The genetic architecture controlling traits measured in this study were also examined. Results found the stay‐green trait was significantly correlated to overall yield (P <.001, r =.37) in rain‐fed environments, but was not significantly correlated to yield (P =.26, r =.09) in irrigated environments. Three quantitative trait loci (QTL) located on chromosomes 2D, 4A, and 4D were associated with the stay‐green trait. The 4A stay‐green QTL, previously designated QGfd.mst‐4A, was collocated with QTL for seed number per head, thousand kernel weight, and heading date. The 4D stay‐green QTL overlaps the Rht‐D1 plant height gene, and the allele prolonging the stay‐green period co‐segregates with the wild‐type (tall) Rht‐D1a allele. Results from this study provide a better understanding of the relationship between stay‐green and agronomic traits in rainfed vs. irrigated environments. Additionally, understanding the genetic architecture controlling stay‐green and agronomic traits will aid in selecting future drought‐tolerant spring wheat varieties. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to present a generalized and a special purpose method for the evaluation of throughput time. The general method presented represents a modification of Mason's Rule to a special ease of flow evaluation encountered in production operations. The algorithm presented is for the special model wherein there is a single output and wherein all possible feedbacks are permissible. It is anticipated that the methods presented will aid greatly in the evaluation and understanding of throughput time. The methods should be equally applicable to normal manufacturing operations and to special major project type activities. Clearly the application of the methods is limited only by one's ability to establish the flow graph, the times for the operations and the yields for the various flows. [ABSTRACT FROM AUTHOR]

Variability of production environments challenges wheat (Triticum aestivum L.) breeders to develop genotypes with the potential to perform well under different levels of resource availability. An important trait that may provide plasticity to wheat is productive tiller number (PTN). This paper reports two studies. The first study tested the impact of a quantitative trait locus (QTL) for PTN on yield and other traits in a set of near-isogenic lines (NILs) grown over nine environments in the Pacific Northwest. Results showed that an allele for high tiller number at QTn.mst-6B enhanced early tiller (ETN) formation regardless of environments. Under favorable conditions, the large number of early tillers translated into a capacity for high PTN. Seed weight and seed diameter were negatively affected by the QTn.mst-6B high tiller allele. The second study assessed the impact of QTn. mst-6B under different competition and soil resource levels in three trials in Bozeman, MT. Three treatments were imposed on NIL pairs in replicated experiments: (i) bordered rows that limited soil resources to each NIL, (ii) nonbordered rows with less competition that provided more soil resources to each NIL, and (iii) space-planted plants with limited competition for soil resources. Results complemented those found in the multienvironment trials, as the high tiller allele caused high PTN at low competition levels when soil resources were more abundant. Increased yield as a result of the high tiller allele at QTn.mst-6B was only detectable in the highest resource treatment and environment. [ABSTRACT FROM AUTHOR]

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 solidstemmed 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. [ABSTRACT FROM AUTHOR]