Soybean Seed Appearance and Quality

  • Soybean seed size and appearance can be affected by the challenging growing conditions experienced in some regions from year to year.
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  • However, soybean seed appearance normally does not affect quality. Seed that looks almost perfect can have poor germination rates while seed that appears flawed may actually be very high in quality.  
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  • Growers should focus on germination rate and the ability of seed to produce a healthy seedling as they place seed orders for the next season.  
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Common Soybean Appearance Problems

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Environmental and disease issues from each growing season, combined with a few storage challenges since harvest, can lead to some seed beans with poor appearance. However, poor appearance is not necessarily an indicator of poor quality.  Likewise, almost perfect looking seed can have poor germination. Conditions such as drought, aphids, viruses and other pathogens, bean leaf beetles, and a quick harvest drydown may lead to various conditions that can cause poor seed appearance. Low harvest moisture can increase the chances of mechanical damage from handling during conditioning and packaging. Rapid shutdown of soybean plants at harvest can create immature green seeds. Excess moisture in bins can contribute to surface mold on seed.  Germination rate, not appearance, should be the focus as several conditions that cause poor seed appearance and surface mold do NOT affect germination. 

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Seed selection should be based on agronomic characteristics (disease tolerance, standability, maturity) rather than seed appearance or size. Year-to-year variations and individual production environments can influence seed size within the same product. To help maximize yield potential, proper planter adjustments and maintenance should be addressed to plant the desired seeds at the appropriate rate.

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Seed Coat Damage (Figure 1) can occur during harvest and the handling process when seed is dry and humidity is extremely low. Chips, cracks, and broken seed result from mechanical damage. Asgrow® brand handling equipment is designed to handle seed gently and to reduce mechanical damage. Asgrow brand conditioning equipment removes most mechanically damaged seed during the cleaning process.

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Growth Marks (Figure 2) may be created as seed coat development is influenced by genetic and environmental factors.  Highly specialized cell layers within the soybean seedcoat rapidly change as the seed develops.1  Genetic expression also changes during seed development and can be influenced by conditions in the environment.  

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Figure 1. Seed coat damage often takes place at harvest when seed is dry and humidity is extremely low. Chips, cracks, and broken seed result from mechanical  damage. 
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Figure 2. Growth marks usually result when the seed coat does not close completely. The cause is not entirely understood, but is believed to result when the seed embryo develops faster than the seed coat.
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Bleeding Hilum (Figure 3), also known as seed coat mottling, can be caused by specific genetics, stresses during seed development, or by soybean mosaic virus. Bleeding hilum does not indicate that the virus is present in the seed.  Transmission of the soybean mosaic virus from seed to plant may be less than 5 percent in most soybean products.2 
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Purple Seed Stain (Figure 4) is caused by the fungus Cercospora kikuchii and causes a purple seed discoloration. In cases with mild seed infection, the coat may be shed before seedling infection can occur. In more severe cases, it can be transmitted from the seed coat to the seedling as the seed germinates and infected seedlings may show a reduction in growth.3 Soybean seed treatments can help prevent transmission of Cercospora to the germinating seedling. 
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Green Coloring (Figure 5) can be found in areas where fields planted later than normal were hit by an earlier than normal frost. The green tint occurs because the chlorophyll has not dissipated entirely. The coloring has no effect on quality if the seed is fully mature. 
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Figure 3. Bleeding hilum can be caused by specific genetics, stresses during seed development, or by soybean mosaic virus.
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Figure 4. Purple seed stain is caused by Cercospora fungus. Effects on germination are slight and only occur when seed is completely purple.
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Soybean Seed Treatments

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Wet, poorly drained soils, common during spring planting and crop emergence, favor the development of the fungal pathogens that cause soybean seedling diseases. These diseases may slow germination and plant growth. Early-season insect pest feeding can damage soybean seeds and seedlings, which can cause adverse effects on plant growth. Seed treatments can help protect seed and seedlings from labeled pests, and result in more uniform plant stands, better yield potential, and ultimately an increase return on investment. Acceleron® Seed Treatment Products have been selected to compliment Genuity® Roundup Ready 2 Yield® and Roundup Ready® soybeans by helping to protect soybean seeds and seedlings from disease and insect damage. 

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Acceleron® Seed Treatment Products contain advancements in seed treatment technology, including multiple modes of action, broad spectrum of control of insects and diseases with increased length of protection. Acceleron Seed Treatment Products provide control for the diseases Pythium, Phytophthora, Fusarium, and Rhizoctonia, and protection from key insects, such as bean leaf beetle, soybean aphid, seedcorn maggot, wireworm, and white grub. Protection from Acceleron Seed Treatment Products can last for up to 30 days. Acceleron Insecticide/Fungicide Seed Treatment Products for soybeans will contain the fungicides pyraclostrobin for Fusarium and Rhizoctonia control, metalaxyl for Pythium and Phytophthora control, and fluxapyroxad for control of Fusarium and Rhizoctonia, as well as the insecticide imidacloprid which provides both above- and below-ground insect protection.

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Seed treatments can help protect fragile seed from soil pathogens.  High quality seed lots that meet the strict germination standards can be planted first and those seed lots suspected to have reduced vigor can be planted later in the planting season in more ideal soil conditions.  Seed with damaged seed coats may absorb water rapidly and should be planted when soil moisture and rains will be warmer.  

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Figure 5. Green coloring can be found in areas where fields planted later than normal were hit by an earlier than normal frost.
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