Hexaploid bread wheat (Triticum aestivum L.) and tetraploid durum wheat (Triticum durum Desf.) have been cultivated in similar geographic areas for ∼10,000 yr. The crossing barrier caused by ploidy difference suggests that different favorable alleles for yield-related traits may have accumulated in the two crops. Previous work allowed identification of favorable alleles at six quantitative trait loci (QTL) from durum wheat in a recombinant inbred line (RIL) population from a cross of 'Mountrail' durum and 'Choteau' spring wheat. The purpose of this study was to determine the impact of six durum alleles at yield component QTL in several spring wheat backgrounds. Three spring wheat cultivars were crossed with six hexaploid lines derived from the original Choteau/Mountrail cross to generate RILs. Heterozygous RILs, containing both the durum and the bread wheat alleles, were identified for each of the QTL. The heterozygous RILs were used to develop near-isogenic lines (NILs) for the six introgressed QTL. The NILs were grown in five environments under irrigated and rainfed conditions in Montana in 2017 and 2018. A durum allele QTL on chromosome 3B resulted in increased kernel weight in all five environments. The introgressed durum QTL alleles caused pleiotropic interactions among yield component traits. Environment and genetic background significantly affected the stability of introgressed QTL on yield components for four of the six QTL. Results suggest that alleles from durum may be useful for yield improvement of hexaploid spring wheat. However, interrelationships of yield components, pleiotropic interactions, and environment will affect the value of durum wheat alleles in hexaploid wheat backgrounds.

Key message Investigation of resource availability on allele effects for four yield component quantitative trait loci provides guidance for the improvement of grain yield in high and low yielding environments. Abstract A greater understanding of grain yield (GY) and yield component traits in spring wheat may increase selection efficiency for improved GY in high and low yielding environments. The objective of this study was to determine allelic response of four yield component quantitative trait loci (QTL) to variable resource levels which were manipulated by varying intraspecific plant competition and seeding density. The four QTL investigated in this study had been previously identified as impacting specific yield components. They included QTn.mst-6B for productive tiller number (PTN), WAPO-A1 for spikelet number per spike (SNS), and QGw.mst-3B and TaGW2-A1 for kernel weight (KWT). Near-isogenic lines for each of the four QTL were grown in multiple locations with three competition (border, no-border and space-planted) and two seeding densities (normal 216 seeds m −2 and low 76 seeds m −2 ). Allele response at QTn.mst-6B was driven by changes in resource availability, whereas allele response at WAPO-A1 and TaGW2-A1 was relatively unaffected by resource availability. The QTn. mst-6B.1 allele at QTn.mst-6B conferred PTN plasticity resulting in significant GY increases in high resource environments. The gw2-A1 allele at TaGW2-A1 significantly increased KWT, SNS and GPC offering a source of GY improvement without negatively impacting end-use quality. QGw.mst-3B allelic variation did not significantly impact KWT but did significantly impact SPS. Treatment effects in both experiments often resulted in significant positive impacts on GY and yield component traits when resource availability was increased. Results provide guidance for leveraging yield component QTL to improve GY performance in high-and low-yield environments.

Background and objectives Hard red spring wheat (Triticum aestivum L.) (HRSW) is used for bread baking while durum wheat (Triticum turgidum L. ssp. durum) is used for pasta production. This study investigated the impact of alleles from durum wheat for yield component traits on HRSW end‐use quality traits. Near‐isogenic lines for four quantitative trait loci, QGw.mst‐3B, QGw.mst‐7A, QTn.mst‐5B, and QYld.mst‐2B, were evaluated in rainfed and irrigated environments. Findings Durum alleles were found to significantly impact end‐use quality at all four loci. The durum allele QGw.mst‐3B for increased kernel weight (KWT) positively impacted end‐use quality traits with increases in kernel protein and loaf volume. The durum allele at QTn.mst‐5B delayed heading date, impacting productive tiller number and KWT and additional end‐use quality traits. The durum allele at QYld.mst‐2B for GY showed both positive and negative effects on end‐use quality. The durum allele for reduced spikelet number per spike at QGw.mst‐7A had little to no impact on end‐use quality. Conclusions Results from the present study indicate that the alleles from durum wheat are potential sources of cultivar improvement; however, interactions between yield component and end‐use quality traits may influence utilization. Significance and novelty This study demonstrates the potential utility of introgressed durum yield component alleles for genetic improvement in HRSW.