Identifying QTLs for dynamic photosynthesis in barley

Improving crop plant photosynthetic efficiency in dynamic environments has recently been highlighted as a key target to increase whole-canopy carbon assimilation. Physiological responses to fluctuating light are particularly important for lower canopy leaves. The light environment of the lower canopy is subject to continuous and dynamic change across the course of a day, caused by movement of the sun across the sky, sporadic cloud cover and/or movement of upper elements in the canopy caused by wind.

Improving Rubisco activation rate in fluctuating light could be the low-hanging fruit that allows plant breeders to boost whole-canopy photosynthesis with few associated costs, specifically in terms of water and nutrient use. This is critical for a future where global environmental change is predicted to leave agricultural systems exposed to more frequent and more extreme drought and heat events. However, no study to date has investigated or performed trait dissection for Rubisco activation in a segregating mapping population of an important crop species.

In our new article published in AoBP, we present the results of a study in which we sought to identify and characterize genetic variation in Rubisco activation rate across a barley (Hordeum vulgare) doubled haploid mapping population in planta using gas exchange techniques (Salter et al., 2020). We then used chromosome interval mapping to identify quantitative trait loci (QTL) and closely associated molecular markers that could be used for marker assisted plant breeding.

We found that rates of Rubisco activation were highly variable across the population. A unique QTL for Rubisco activation rate was identified on chromosome 7H. This is the first report on the identification of a QTL for Rubisco activation rate in planta and this discovery could open the door to marker-assisted breeding to improve whole-canopy photosynthesis of barley. We hope that future work will validate these QTLs under field conditions so that they can be used to improve crop yield potential.