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This season has been a stress filled one for the winter wheat crop. Two major ice storms during the winter, the almost record high temperatures for three weeks in late March and early April followed by 4 days of record low temperatures April 4-7, in addition to various insect and disease problems have had a major impact on yield and test weight. The early indications are that yields and test weights may be variable across the state. If wheat is going to be saved for seed, this is certainly a year to pay careful attention to the quality of seed being saved.

In particular, low temperature injury may lead to a number of shrunken and shriveled kernels or to blank kernels and thus low germination rates. Loose smut was again an obvious problem in some fields. And Fusarium head blight or scab was a problem in some fields. Therefore, if growers are saving seed to plant, it is critical that they pay special attention to testing the viability of their wheat seed in 2007.

The first step is to clean the wheat seed. It is important that wheat seed be cleaned to remove small and damaged seed and to eliminate weed seeds. Removing small and damaged seed will not only aid in crop establishment it will also provide a more uniform wheat seedling stand. Removing small and damaged seed will also increase the thousand-kernel weight (TKW), which serves as a measure of seed quality. Wheat seed lots with TKW values greater than 30 grams tend to have increased fall tiller number and seedling vigor.

The next step is to perform a germination test. Germination tests can either be completed at home or by sending a sample to the Missouri Seed 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 percent germination. It is important to choose random seeds throughout the entire seed lot and conduct at least five 100 seed counts. The Missouri Seed Improvement Association also performs a germination test. The test requires one pound of seed and costs $13.75. For details email MOSEED@AOL.com or check the Missouri Seed Improvement Association Website at http://www.moseed.org. If germination is below 85 percent it is important to increase the seeding rate to compensate; however seeding any wheat with a germination test below 80 percent would not be recommended.

The next step is to decide whether a fungicide seed treatment is necessary. A number of fungicides are labeled for use as seed treatment fungicides 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.

As mentioned before loose smut was more common than usual in Missouri wheat fields during the 2007 season. Loose smut is obvious as heads emerge from the boot. All portions of the head except the rachis are converted to masses of dusty black spores. Spores produced on smutted heads are wind carried to adjacent plants in the field and infect those plants through the flowers. Later in the season loose smut is not as obvious as most of the spores on the smutted heads have been dislodged by wind and rain leaving only the bare rachis of the plant.

The fungus which causes loose smut survives within the embryo of the wheat seed. The fungus survives as dormant vegetative strands within the embryo. This infection is not visible to the naked eye and will not be picked up in the standard germination test. If infected seed is planted and germinates, the fungus also begins to grow within the plant, and at heading, the fungus is at the growing tip and produces smut spores where the grain kernels should be. If seed from a field that has a "small" amount of smut in one season is used for seed, the field planted with that seed may have a substantially higher level of smut.

Management of loose smut is through the planting of disease-free seed or the use of a systemic fungicide seed treatment (see accompanying table of wheat seed treatment fungicides). Growers with considerable loose smut should consider seed treatment on this grain next year, if grain must be used for seed. In wheat, infection levels of 2 percent or greater would indicate that seed treatment would be economic.

Fusarium head blight or scab infection may result in shriveled and shrunken kernels, lightweight bleached or tombstone kernels or kernels that have a pinkish cast or discoloration. Lots with high levels of scab may have lower germination rates. The fungus that causes scab can also cause a seedling blight of wheat. If scab infected seed is used for planting, seedling blights and stand establishment problems may occur. Management of Fusarium seedling blight is through the planting of disease-free seed or the use of a fungicide seed treatment effective against seed-borne Fusarium or scab (see accompanying table of wheat seed treatment fungicides). Because scab can decrease germination, a germination test may be especially useful in determining if a particular lot should be used for seed.

Laura Sweets
SweetsL@missouri.edu