Importance of Preliminary Trait Purity Testing in Corn Seed Production

- Brenda Johnson

When producing traited seed, trait purity testing is not an option – it’s both a necessity and a requirement by the trait provider. The seed producer has two options for trait purity testing. One option is conducting trait purity testing on the finished seed lots at the time of bagging only. The second option is testing hand-screened samples as they arrive from the field, also known as preliminary testing. If the hand-screened samples meet trait purity requirements, a reduced number of seeds may be tested during finished seed lot trait purity testing. In other words, is it worth the expense to conduct preliminary testing ahead of conditioning?

“Trait purity testing has significant value to seed producers apart from their licensing agreements with trait providers,” says Brenda Johnson, Registered Genetic Technologist (RST) and Manager-Operations, Eurofins-US, River Falls, Wisconsin. “Ultimately, the value of seed comes down to how well it yields and performs for its end user. This requires that corn seed meets the highest standards for trait and genetic purity. At the same time, seed producers want to manage risk and get the most value from their seed production. For them, knowing an incoming lot’s trait purity can help determined how that seed is sized and conditioned. This is especially important for corn hybrids with male donated traits.”

When best practices for seed production are followed and growing conditions are optimal, the parents nick and pollen is received uniformly throughout the developing ear. But when conditions during pollination are less than ideal – too windy, too hot, too rainy or too dry – the plants do not always nick, and the resulting seed has less than the required male-carried traits. In this sense, no two years are alike, even for the same hybrid.

“A preliminary trait purity test is a risk assessment tool that provides the information a seed producer needs to adjust the conditioning process for a seed lot that might otherwise fail its final test,” Johnson says. “Even when field production follows all the best practices, environmental factors can still play a role. The cost of getting the information needed to salvage a seed lot is far less than the cost of discarding seed that fails its final trait purity test.”

Johnson says that when a seed lot fails a preliminary trait purity test for a male-donated trait, the deficiency can often be isolated by seed size. Resizing strategies can be used to salvage the portion of a seed lot that meets quality standards. Preliminary trait purity testing provides important information that allows the seed producer to prepare for sizing and conditioning operations to maximize the amount of high-quality seed available for sale.