HighlightsCultivar grain yield responses to N limitation associated with N uptake at anthesis.N-use efficiency in thirty wheat cultivars was correlated with timing of flag-leaf senescence.Flag-leaf senescence timing was correlated with N accumulation at anthesis.The yield in N stressed crops was limited by grain source capacity.

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A diverse panel of 245 wheat genotypes, derived from crosses between landraces from the Watkins collection representing global diversity in the early 20 th century and the modern wheat cultivar Paragon, was grown at two field sites in the UK in 2015-16 and the concentrations of zinc and iron determined in wholegrain using inductively coupled plasma-mass spectrometry (ICP-MS). Zinc concentrations in wholegrain varied from 24-49 mg kg-1 and were correlated with iron concentration (r = 0.64) and grain protein content (r = 0.14). However, the correlation with yield was low (r =-0.16) indicating little yield dilution. A subset of 24 wheat lines were selected from 245 wheat genotypes and characterised for Zn and Fe concentrations in wholegrain and white flour over two sites and years. White flours from 24 selected lines contained 8-15 mg kg-1 of zinc, which was positively correlated with the wholegrain Zn concentration (r = 0.79, averaged across sites and years). This demonstrates the potential to exploit the diversity in landraces to increase the concentration of Zn in wholegrain and flour of modern high yielding bread wheat cultivars.

Wheat yields are stagnating or declining in many regions, requiring efforts to improve the light conversion efficiency, i.e. radiation use efficiency (RUE). RUE is a key trait in plant physiology because it links light capture and primary metabolism with biomass accumulation and yield, but its measurement is time consuming and this has limited its use in fundamental research and large scale physiological breeding. In this study, high-throughput phenotyping (HTPP) approaches were used among a population of field grown wheat with variation in RUE and photosynthetic traits to build predictive models of RUE, biomass and intercepted photosynthetically active radiation (IPAR). Three approaches were used: best combination of sensors, canopy vegetation indices and partial least square regression. The use of remote sensing models predicted RUE with up to 70% accuracy compared to ground truth data. Water indices and NDVI are the better option to predict RUE, biomass and IPAR, and indices related to NPQ (PRI) and senescence (SIPI) are better predictors for these traits at the vegetative and grain filling stages respectively. These models will be instrumental to explain canopy processes, improve crop growth, yield modelling, and potentially be used to predict RUE in different crops or ecosystems.

Lodging affects grain quality and grain yield in wheat (Triticum aestivum L.) and is difficult to breed for because its sporadic incidence and laborious protocols to measure lodging traits. Thus, developing molecular markers for these traits can increase selection efficiency in breeding programs. The aim of this article is to identify quantitative trait loci (QTL) associated with stem/anchorage strength and leverage traits (lodging traits) in a doubled-haploid population of UK bread wheat Avalon × Cadenza. Field experiments were conducted in the UK during 2012-2013 near High Mowthorpe and during 2013-2014 at Sutton Bonington. Phenotypic and genetic analysis indicated significant genetic variation for all traits. Stem strength (diameter, wall width, and material strength) and leverage (plant height) traits were highly heritable (0.64-0.95), whereas anchorage strength traits (root plate spread and structural rooting depth) and ear number per plant (leverage trait) were less heritable (0.21-0.33). This study identified 18 QTL for lodging traits and grain yield in chromosomes 1D, 2B, 2D, 3A, 3B, 4A, 4D, 5B, and 6B. Two QTL for stem strength on chromosome 1D and 3B explaining 49.6% of the total phenotypic variation (PVE) are estimated to reduce stem lodging risk and shortening the plant height by 12 cm. One QTL for root plate spread on chromosome 5B explaining 22.4% of the PVE could increase root lodging resistance.