Dissecting the Opposing Roles of Thermal Intensity and Growing Degree Days in Regulating Spring Wheat Protein Content

Area of Science:

• Agronomy
• Plant Physiology
• Climate Science

Background:

• Wheat quality, specifically protein content (PC), is vital for consumer and industrial needs.
• Environmental factors significantly impact crop physiology and yield, necessitating a deeper understanding of their specific roles.
• Distinguishing between thermal intensity and thermal accumulation is key to understanding their differential effects on wheat PC.

Purpose of the Study:

• To differentiate the physiological impacts of thermal intensity versus thermal accumulation on spring wheat protein content (PC).
• To identify key environmental drivers influencing PC variation in spring wheat across Inner Mongolia.
• To provide a physiological basis for optimizing wheat quality zoning under changing climatic conditions.

Main Methods:

• Partial least squares regression (PLSR) was employed to analyze relationships between environmental factors and PC.
• Structural equation modeling (SEM) was used to elucidate the direct and indirect effects of thermal parameters on PC.
• Data were collected across various regions in Inner Mongolia, focusing on spring wheat cultivation.

Main Results:

• Environmental factors were identified as the primary drivers of PC variation.
• The Erguna region exhibited the highest PC (18.53%) despite the lowest growing degree days.
• High thermal intensity during heading-to-anthesis positively influenced PC (path coefficient = 0.965) by enhancing nitrogen remobilization.
• Excessive thermal accumulation and sunshine duration during grain filling negatively impacted PC through a carbohydrate dilution effect.

Conclusions:

• Optimal spring wheat PC formation depends on a precise spatiotemporal interplay of thermal conditions.
• High thermal intensity before anthesis primes nitrogen transport, while low thermal accumulation post-anthesis minimizes carbon dilution.
• These findings offer a physiological framework for strategic wheat quality zoning and breeding under future climate scenarios.