More Emphasis Needed on Seed Quality When it Comes to Treating Seed

- Grass Lahcen

To me, seed safety is an evaluation of the potential impact of a seed treatment on the physiological quality of seed and its ability to perform after limited time in storage.

Syngenta Seed care products go through extensive testing from discovery through the entire lifecycle of the product to assess seed safety. This not only allows us to meet regulatory requirements, but also helps keep our risks to our customers at a minimum, and making sure that customer needs are supported at all times. This high service to our customers are another reason why Syngenta Seedcare is a great partner for seed companies.

Our ultimate goal is to ensure treated seed maintains its inherent vigor and germination during storage. Through this validation process we want to protect growers’ investment in high quality seed and traits, and we don’t want to apply a seed treatment that is going to decrease germination.

Seed safety testing requires the evaluation of a number of characteristics for a crop. These include, but are not limited to, treatment recipes and rates, germplasm, initial seed quality, seed moisture, carryover period, and testing methods and frequency.

After we look at these factors, then we can set up the study. The two biggest influencers are the testing methods used and the initial quality of the seed being tested.

It is absolutely critical to start with high quality seed, because this will affect the performance of treated seed. If the seed doesn’t germinate in the field, the first thing a grower might think is that the seed treatment may have impacted the seed. However, evidence from extensive testing across crops has shown that decline in the performance of treated seed is mainly a consequence of lower initial seed vigor that accompanies natural seed aging, and is not a direct consequence of seed treatment.

It is important to note that the quality of a given year’s seed is determined by the prevailing weather and field conditions from the previous year, and subsequent processing and handling practices, and was at its highest point at physiological maturity. It is our job to preserve and maintain this quality until seed is needed for planting. Among other best practices, seed treatment usually helps to achieve this goal.

High quality seed is determined by its parent’s genetic makeup, physical integrity and purity of the seed, seed health, and physiological seed quality. The latter property is determined by two separate tests, a germination test and a vigor test.

However, these tests are not created equal. For seed to be sold in the United States, percent germination must be printed on each bag of seed. This value is derived from a standard germination test conducted under optimum temperature, moisture and light conditions.  However, some of these seed lots may not be capable of germinating or emerging under less than optimal field conditions, or so called “stress.”

As we look at vigor, a different story takes shape. This is a non-standardized test, and each seed company has its own proprietary slightly different method for conducting vigor tests. But, the common theme is that vigor tests generally impose a stress on the seed to determine its ability to perform well under stressful conditions, and “stressful” is the keyword.

In fact, high germination seed lots from the same variety and year can yield good germination test results but score very different on vigor tests. Generally, seed susceptibility to stresses that lead to poor and uneven field emergence are typical features of seed with lower vigor, not of lower germination capacity. On the other hand, higher and uniform emergence and vigorous seedling growth are properties of seed with higher vigor and germination.

To get a complete picture, all our seed safety studies include high germination seeds but different levels of seed vigor and are evaluated by both tests at storage intervals of zero, six, 12, 18 and 24 months. The picture below shows germination and vigor results for treated corn after 18 months in storage for seed lots A and B from the same hybrid. Both seed lots maintained their seed germination over time, but showed significant differences when it came to seed vigor scores. The lower the initial seed vigor, the faster untreated or treated seed deteriorates. In fact, the impact from these differences in seed vigor can start as early as three to six months into storage depending on the crop.

For this reason, when testing seed for treating, it is imperative that we, as an industry, increase the awareness of seed quality and the crucial role of seed vigor testing. We ask that you always run a vigor test on seed before it is treated. It is a second but essential screening tool that helps you rank high germinating seeds into good and poor quality seed lots, and it can be a powerful tool for inventory management, planting decisions as well as marketing.