Winter Wheat Variety Selection and Seed Quality 

Shawn Conley, John Gaska, Craig Grau

Near record wheat and straw prices coupled with moderate to severe drought conditions has lead to an increase in wheat seed demand for the 2007-08 growing season. As with any crop, variety selection is the most important factor to consider in maximizing winter wheat yield and profitability. When choosing a soft red winter wheat variety several factors must be considered. These include winter survival, insect and disease resistance characteristics, heading date, lodging, test weight, and most importantly, yield. Since no variety is ideal for every location it is important to understand the crop environment and pest complex that affects your specific region in order to maximize yield. 

Yield is based on the genetic potential and environmental conditions in which the crop is grown. Therefore, by diversify the genetic pool that is planted, a grower will hedge against crop failure.  Yield data and yield stability characteristics can be attained from the UW Winter Wheat Variety trial results. Select those varieties that perform well not only in your area but across experimental sites and years. This will increase the likelihood that given next years environment (which you cannot control) the variety you selected will perform well.

Test weight is also an important factor to consider when selecting a variety. The minimum test weight to be considered a U.S. #2 Soft Red Winter Wheat is 58 pounds per bushel. Wheat with a test weight lower than 58 pounds will be discounted. Both environment and pests may greatly affect test weight, therefore, selecting a variety that has a high test weight potential in your region is critical to maximize economic gain.

Select a variety that has the specific insect and disease resistance characteristics that fit your regional needs. By selecting the appropriate resistant varieties, crop yield loss may be either reduced or avoided without the need of pesticides. Careful management of resistant cultivars, though crop and variety rotation is required to ensure that these characteristics are not lost.

Crop height and lodging potential are also important varietal characteristics that may be affected based on cropping system. If the wheat crop is intended for grain only, it may be important to select a variety that is short in stature and has a low potential for lodging. This may decrease yield loss due to crop spoilage and harvest loss as well as increase harvest rate. However, if the wheat crop is to be used as silage or to be harvested as both grain and straw then selecting a taller variety may be warranted.

Seed Quality

The next step in maximizing crop yield is planting high quality seed. Plant certified or private (professionally prepared) seed that is true to variety, clean, and has a high germination percentage (>90%). Seed size is also an important factor in determining seed quality. Select varieties that have large dense kernels and a thousand kernel weight (TKW) greater than 30 grams. A TKW of 30 g is ~15,100 seeds/lb. Wheat seed with TKW values greater than 30 grams tend to have increased fall tiller number and increase seedling vigor. This is especially important to consider with late planted wheat.   

If saved seed is to be planted due to a lack of seed availability in 2007 it is critical to clean the seed. Seed cleaning will remove weed seed, chaff, as well as small and broken seed thus increasing seed quality. It is also important to perform a germination test. If the germination percentage is below 90%, increase the seeding rate accordingly; however do not plant seed with a germination test below 80%. If it is known beforehand that seed is to be saved, scout and choose seed from fields where diseases and weeds were minimal.

The next step is to perform a germination test. Germination tests can either be completed at home or by sending a sample to the Wisconsin Improvement Association. A home test can be performed by counting out 100 seeds and placing them in a damp paper towel. Place the paper towel into a plastic bag to conserve moisture and store in a warm location out of direct sunlight. After five days count the number of germinated seeds that have both an intact root and shoot. This will give the grower an estimate of % germination. It is important to choose random seeds throughout the entire seed lot and conduct at least 5 - 100 seed counts. The Wisconsin Improvement Association also performs a germination test. The test requires 1.25 pounds of seed and costs $10.00.  If germination is below 85% it is important to increase the seeding rate to compensate; however, I would caution growers from seeding any wheat with a germination test below 80%.

The next step is to assess whether to apply a seed treatment.. A number of fungicides are labeled for use as seed treatments on winter wheat. These seed treatment fungicides protect germinating seed and young seedlings from seedborne and soilborne pathogens. Seed treatment fungicides will not improve germination of seed that has been injured by environmental factors and will not resurrect dead seed. A correct assessment of the cause of poor seed quality or poor germination rates is the first step in deciding if a seed treatment fungicide is necessary. Research from the 2006-2007 growing season indicated a significant yield response from several fungicide seed treatments in wheat (Table 1).

 Table 1. Seed Treatment Effect on Soft Red Winter Wheat Grain Yield at the Arlington Research Station (WI) in the 2006-2007 Growing Season.

Seed Treatment	Grain Yield (bu per acre)
Untreated	80.3
ApronXL	88.3
Charter + ApronXL	91.1
EXP #1	89.4
EXP #2	81.7
Charter PB	93.0
Dividend Extreme	89.7
Dividend Extreme D	96.9
Raxil Thiram	89.1
Raxil MD	89.0
EXP #3	83.2
EXP #4	81.0
EXP #5	78.6