Global warming is a serious concern for agriculture. The Intergovernmental Panel on Climate Change has projected a global warming trend of 0.3-1.7ºC by 2100. As temperatures increase, heat waves (a phenomenon when temperatures are exceptionally high for a continuous period of several days) will become more frequent, longer and severe.

Pre-anthesis heat stress affects yield mainly by increasing floret mortality, either by direct or indirect effects, and thus reducing the number of grains. Post-harvest heat stress also affects yield by impairing grain development, resulting in lower grain weight, although it may also cause kernel abortion. In addition to this, heat stress during grain development also affects the deposition pattern of phytochemical compounds, thus impacting on grain quality.

The yellowness of pasta and couscous is the first attribute that consumers evaluate when determining the quality of a cereal-derived food product, which determines its acceptability and consumption. Carotenoids are responsible for the yellow colour of durum wheat grains, making it an important quality target for durum wheat breeding worldwide.

In this work, we investigated the impact of Short Heat Waves (SHW) during grain development on grain carotenoid content and profile in durum wheat. Four durum wheat varieties, ‘Don Ricardo’, ‘Don Ortega’, ‘Athoris’ and ‘Amilcar’ were used. Together, these varieties represented almost 50% of the market share in Spain during the 2022-2023 season.

For the experimental trials, heat stress conditions were imposed by installing structures (1.5 m height, 1.5 m width, 1.5 m long) over the field plots. These structures were covered with 125 µm transparent polyethylene film, but leaving the bottom 30 cm of each side open to facilitate gas exchange.

SHW impacted total grain carotenoid content and thousand kernel weight with reductions around 25% and 8% respectively, on the contrary no changes in grain protein were observed. Thus, heat stress is not only a concern regarding yield but also grain quality in Mediterranean environments.

Acknowledgements

Project TED2021-130426B-I00 funded by MICIU/AEI/10.13039/501100011033 and by European Union NextGenerationEU/PRTR.