Testing Strategies for Seed Corn Exposed to Freezing Temperatures
Once a freeze event occurs, seed corn producers need to determine if seed quality has been affected. If a significant number of fields remain to be harvested after the freeze event, testing may be used to prioritize decisions regarding harvest. If harvesting priority is not an issue, testing can be used to determine if the affected seed lots experienced significant physical or physiological damage.
One of the best practices to evaluate freeze damage is to collect and dry a random sample of ears from each field prior to the freeze event. The testing data from these ears can be used as a reference point for quality against the post-freeze harvested ears.
Testing for Harvesting Prioritization
Hand harvest ears representing areas of greatest concern or at random from within uniform fields. Dry ears down to below 15% seed moisture in plastic mesh bags (onion bags). Shell, grade, and submit to SGS for testing. Tetrazolium testing (TZ) is the quickest method to determine if seeds are showing physiological damage from freezing. Freezing commonly affects the growing points and scutellum tissue viability. TZ testing results are available on our website within 24 hours of receipt.
Post-Freeze Event Testing Options
Physical Quality – Freezing temperatures can cause damage to the pericarp. A pericarp damage test (fast green), can be useful in finding the level of pericarp separation within seeds lots. Seed lots with high levels of pericarp separation can experience pericarp flaking or can lose the entire pericarp with time and/or additional handling.
Physiological Damage – Freezing or ice crystal formation can cause cell wall and/or respiratory organelle damage, which results in reduced quality and longevity. Several tests can be useful in determining the storability/salability of seed lots.
Standard Warm Germination – Can determine sugar leakage (RH rating), swollen mesocotyls (SM), slow plumule growth and detached peeling pericarps (PP) can all be symptoms of frost damage.
Electrical Conductivity (EC) – Measures cell leakage and can be useful, especially to compare “before” and “after” freeze samples. High EC values indicate more seed deterioration.
Accelerated Aging (AA) – A high heat and humidity stress test that is most useful as a predictor of shelf life. If AA values are below baseline values, seed may not maintain the desired quality level.
Saturated Cold – Provides a high respiratory stress that may help select seed lots with shorter shelf life. It is very desirable to have both pre and post-freeze samples for comparison.
Tray Cold – Most useful for pre and post-freeze sample comparisons.
For more information, please contact:
236 32nd Avenue
Brookings, SD 57006, USA