Wheat is one of the main staple food crops, providing an essential source of carbohydrates for millions of people. Therefore, demand for wheat will increase in next few decades as the global population increases toward a prediction 9 billion by 2050. Further advances in wheat yield requires the integration of new tools and strategies to complement traditional approaches to select genotypes that are better suited to abiotic stress, in the context of climate change. Identifying morphological and physiological characters, correlated with tolerance to environmental stress, is a priority for wheat breeders. One approach that can be combined in wheat breeding programmes is to create new genetic variation, for example by crossing wheat with close relatives such as spelt. The overall objective of this study is to investigate the physiological traits associated with radiation use efficiency (RUE) in a segregating population of 225 recombinant inbred lines, originating from the cross of wheat (cv. Forno) with spelt (cv. Oberkulmer). Three field experiments from 2010 to 2012 were carried out at Sutton Bonington. All lines, and their parents, were grown as ear rows in 2010 and arranged in randomized design with one replicate of mini plots in 2011. In 2012 three replicates were grown in a randomised complete block design. In these experiments, plant development, RUE, biomass, grain yield and associated physiological traits were measured in the recombinant inbred lines. In addition, a glasshouse experiment was conducted in 2013 to investigate gas exchange traits amongst 18 selected lines with a wide range of RUE, alongside the parents.