Importance of Wheat Varietal Differences in Grain Test Weight

Bill Bruening, Scientist III

University of Kentucky, Lexington  

INTRODUCTION (objective) 

Wheat test weight is important because it serves as a crucial indicator of grain quality, impacting a farmer's marketability and price for the crop, as well as the milling yield and quality of the resulting flour. Higher test weights often correspond to higher prices and better flour extraction, with lower weights leading to discounts from grain buyers. Test weight also relates to the energy content and feeding value of wheat for livestock, though this impact is less significant than it is for grains like corn.

The heritability of wheat test weight is generally high, with estimates for broad-sense heritability often exceeding 70% and frequently above 90% in various studies. This indicates that genetic factors play a significant role in determining test weight, making it a suitable trait for selection during the wheat breeding process. The heritability of wheat yield, by comparison, is complex and can vary significantly, but is generally considered moderate, with some studies showing ranges from around 30% up to 70%. While environmental factors can influence test weight, the substantial genetic component means that breeders can effectively select for improved test weight through genetic means. Likewise, growers can select for high test weight when making variety selection decisions.

RESULTS & DISCUSSION

The University of Kentucky variety testing program annually evaluates wheat varieties for differences in grain, forage and straw yield potential, as well as disease reaction and grain test weight. In recent years, environmental conditions in Kentucky have caused a reduction in test weights and farmers have faced corresponding price dockages from buyers. While farmers usually prioritize high grain yield potential when selecting wheat varieties to plant, there are varieties that exhibit both high grain yield potential and test weight. Click HERE to view the variety test results. Table 1 shows the top 20 highest yielding varieties (highlighted in yellow), sorted by test weight. It is clear that high yielding varieties vary in test weight potential.

Data (Excel files) is accessible at https://varietytesting.ca.uky.edu/wheat for annual variety selection decisions.