Wheat Kernel Protein
By Sue Mondal — In 2024, winter wheat grain yields were near a record high of 50bu/ac. Even though the grain yields were higher a major concern that has been reported is the lower-than-normal protein ranging between 9-11 percent, resulting in discounts at elevators.
Wheat kernel (grain) has three main contents: bran, endosperm and germ (Fig1). Endosperm accounts for nearly 83 percent of the kernel weight and is primarily composed of protein and carbohydrates. Protein is formed from the nitrogen that is mobilized from the leaves and stems of the plant. Nearly half of the protein in the kernel is assimilated within the first 20 days of flowering, after which carbohydrates start moving into the kernel, thus a longer grainfilling period resulting in high yields. In a year with high yields, the proportion of carbohydrates is higher in the grain resulting in lower protein, and vice versa if there is drought or high temperatures or other plant stresses; the kernel has less carbohydrates and higher percent protein.
Protein percent in a wheat variety is not only dependent on the variety being grown, it is influenced by environmental factors and fertilizer management. Adequate levels of nitrogen are an important management factor to yield and protein in wheat. In 2024, with a wet spring in most of Montana, an additional midseason top-dress of nitrogen may have boosted the protein percent. Whether or not a top-dress application has a good chance of increasing protein can be determined by measuring flag-leaf N concentration. Studies showing protein response to top-dressing based on flag-leaf N tend to be more reliable for winter wheat than spring wheat. Despite challenges, proper selection of varieties and fertility management can help achieve high yields while maintaining grain protein.
The MSU winter wheat breeding program annually evaluates all breeding material in different stages of the breeding advancement and field testing for protein content to ensure selection of lines which not only have high yield and adaptation, but also maintains protein content.