Originally called the “Fast Green Test”, the Pericarp Damage test is commonly used in many quality assurance programs to determine pericarp (seed coat) integrity, sources of damage to the seed and provide an estimate of seed quality. It can assist corn seed producers with the following:
§ Determine if certain genetics are predisposed to thin pericarp.
§ Help pinpoint steps in conditioning where excess damage is occurring to seed.
§ Samples taken at each step of conditioning can be tested to identify equipment or procedural changes needed to reduce rough handling of seed.
§ An increase of damaged seed at any one step is an indicator of faulty equipment that may need adjusting, repair or replacement.
§ Can be a useful tool during a company audit to explore options to reduce the amount of damage to seed and aid in improving the quality of the final product.
§ Provides a quick estimate of seed quality.
Why should I be concerned about pericarp integrity?
The pericarp performs many important functions for the seed including: imbibition control, protection against microbial and fungal infestations and seed nutrient containment. Seed imbibes water at a rate controlled by the seed coat and imbibitional damage can occur if cracks in the seed coat allow water to enter too quickly. This can cause some cells to swell and burst. If the pericarp is damaged, nutrients and sugars may leak from the seed which may decrease the available food supply to the seedling and greatly increase the chances of microbial and fungal infestations injuring or killing the seedling.
How does the test work?
The sample is placed in a dye solution, stirred for 15-30 seconds to allow infiltration of the dye, rinsed in water for 5-10 seconds and then blotted dry. The dye enters into any crack, abrasion or fissure in the seed coat. These cracks may not be seen by the naked eye, but are apparent after the dying process. The dye will also enter the spaces created by pericarp separation caused by frost damage. A contrasting color dye is used so the stained areas are evident and not confused with seed treatment.
Why would seed production companies use this test for their conditioning process?
A higher percentage of medium & severe damage indicates excessive damage to the seed. This can be correlated to seed performance in other laboratory tests. Cracks and fishers in the seed coat promote microbial infestation and the loss of sugar and nutrients through these cracks decreases the ability of the seed to produce a seedling. Areas of the embryo that protrude are in danger of being damaged during conditioning and handling. Seeds with severe damage are the most likely to produce seedlings with abnormal growth. Abrasions, nicks or gouges can severely impact the rudimentary plant just under the pericarp and can lead to shredded leaves, stunted shoots, and damaged or absent roots. Percentages of each of the three levels of damage (light, medium and severe), are recorded and are reported to the customer but the combined percentage of the medium and severely damaged seed should be of concern.
Figure 1. Light damage - only light abrasion damage to tip (pedicel) and pericarp near tip. Damage confined to lower ¼ of embryo region.
Figure 2. Medium Damage - shows damage at least ¼ down the embryo from the pedicel end and consists mainly of abrasion damage along sides of embryo. Impacts may be present, but not over embryonic axis.
Figure 3. Severe Damage - impact damage must be present and over the embryonic axis to be considered severe. Greater than 10% severe damage is a concern and usually results in lower germs.
Post-Freeze Event Pericarp Testing Options
Freezing temperatures often cause damage to the pericarp. The pericarp damage test can be useful in finding the level of pericarp separation within seed lots. Seed lots with high levels of pericarp separation can experience pericarp flaking or lose the entire pericarp with time and/or additional handling. Freezing may cause the pericarp to separate from endosperm.
If you have fields that have experienced frost damage, SGS MWSS suggests sending in samples for TZ analysis and a Pericarp Damage – Frost test. Results from the Pericarp Damage – Frost test are reported as the percentage of kernels showing pericarp separation and are not classified as light, medium or severe.
Brad Farber - Corn Laboratory Manager