Prolonged heat and drought versus cool climate on the Swedish spring wheat breeding lines: Impact on the gluten protein quality and grain microstructure

Fluctuating climate, heat, and drought are expected to considerably impact bread wheat (Triticum aestivum) quality in the coming years and, as wheat is an essential food element worldwide, this will have significant implications for future food security and the global economy. This leads to an urgent need for developing wheat varieties with stable yield and gluten quality. In this study, we investigated the effect of heat and drought, compared to a cool climate, on gluten proteins in 294 spring wheat genotypes grown in 2017 and 2018 in Sweden. Gluten protein parameters were studied by size exclusion high-performance liquid chromatography (SE-HPLC) and grain morphology by X-ray tomography. The prolonged heat and drought led to: (i) increased gluten polymerization and the formation of large polymers, as defined by the percentage of unextractable polymers in total polymers (%UPP) and the percentage of large unextractable polymers in total large polymers (%LUPP); and (ii) increase in large monomers, as defined by the percentage of large unextractable monomers in the total large monomers (%LUMP) and the ratio of monomers versus polymers (Mon/Pol) in the flour. The cooler climate also led to an increase in total protein concentration and accumulation of the monomeric proteins and total SDS-extractable proteins (TOTE). No difference in the total amount of SDS-unextractable proteins (TOTU) was found between the studied climates. Due to the heat and drought stress, the grain yield decreased in most of the genotypes, while the grain microstructure varied only to a minor extent. The wheat genotypes identified in the study that provide good yields and stable gluten properties in both prolonged heat-drought and cool environments are strong candidates to contribute to a secure, self-sufficient future wheat supply in the face of an evolving climate in Sweden and in similar climates worldwide.