Whether you know it not, you probably observe, discuss and consider G x E x M several times through the growing season, and into the winter months, when you make decisions regarding the hybrids and varieties you will plant each year. You may call it something else, but plant breeders call it Genotype by Environment by Management Interaction – or G x E x M. Simply stated, G x E x M is the change in relative performance of hybrids and varieties across different environments and management systems.

 

G x E x M is the reason why Hybrid A outperformed Hybrid B by 20 bushels per acre on your farm, but did just the opposite on your neighbor’s farm. It’s the reason Variety A did so well when planted early, but did so poorly when planted late. And it’s the reason why Hybrid C lodged so badly on your farm, but stood like a trooper for your neighbor. The list could go on and on.

 

Product characteristics interact with environmental conditions and management practices. It’s this interaction that causes the relative performance differences described above. If no interaction existed, performance among products would be the same across all environments. That just doesn’t happen, at least not across a significant number of environments.

 

G x E x M interactions occur in two ways. First, the difference among hybrids or varieties can vary, but their rank remains the same. In this case, Hybrid A always outperforms Hybrid B. The performance difference can be small or large, but Hybrid A always wins. In the second case, the rank among hybrids or varieties changes with environmental conditions. Variety A yields more in some environments while Variety B yields more in others. The G x E x M interaction of most concern to breeders, and others, is the one causing changes in the rank among products.

 

Most seed suppliers evaluate G x E x M interactions of experimental products for several years before they introduce them commercially. If not, they could be in for a surprise or two when a new release is planted large-scale. We could cite several examples from our experience in the seed business of products that were “rushed to market.” Plant breeders will most likely drop products with little stability – those with a large G x Ex M – from further testing, unless the specific conditions favoring their performance can be identified and the producer is willing and able to plant them as required.

 

More and more seed suppliers are realizing the importance of proper product positioning and are discussing product weaknesses and how to manage them for maximum performance. This is great and, as long as the producer understands the product limitations and accepts the responsibility for proper placement, things are fine. When a producer forgets these limitations and product performance is less than expected, the seed supplier is often blamed – at least until the producer is reminded of the placement limitations. The producer then either accepts responsibility and tries again or he decides that the product requires more “attention” than he is willing to give, and he buys something else.

How did the hybrids and varieties you grew this year perform relative to your expectations? Now is the time to evaluate performance and make selections for 2008. Based on this discussion, you should carefully review G x E x M. You don’t want to drop products that have potential on your farm if positioned properly; nor do you want to keep products that may have “lucked out” but are otherwise poor performers. The more locations and years your information source comes from, the better.

Product characteristics – There are no perfect hybrids or varieties. Every product has a weakness. Good hybrids and varieties have more strengths than weaknesses. That’s what makes them good. Many weaknesses can be overcome by proper management and placement. Corn hybrids with weak stalks, for example, are generally not recommended for high seeding rate or where stress conditions are likely. The key to product selection is selecting products that offer the best combination of characteristics for the specific needs of each field, or areas of a field, in your farming operation.

 

Field data – To determine characteristics needed, list the factor or factors most often limiting yield potential in each field. Don’t place too much emphasis on the previous year or any one year in particular. Several years’ experience should be considered. From the list, separate factors that are product related from those that are management related. Stand establishment can be both product and management related. In this article, we are focusing on product characteristics.

 

Management factors – Once the list of management related factors is complete, rate the frequency that each limits yield potential. If standability is a problem 3 years out of 5, for example, give it a 60% rating. Although all factors are important, you will want to focus on those that most frequently limit yield potential. Factors that are a concern more than 50% of the time should be highlighted. If the highlighted list is small, you are already doing a good job of selecting and positioning products for maximum performance. Work to lower the frequency percentage, highlighting a few more factors, and focus on them in 2008. If your list is long, you have a great opportunity to improve production levels.

 

Hybrid ratings -- The hybrids and varieties you select for production should be rated strong for performance characteristics associated with the yield-limiting factors you have identified. For example, if stand establishment is a problem, select hybrids and varieties rated strong for emergence and early vigor. If standability is a concern, select hybrids and varieties rated strong for root and stalk strength. Typically, there are no extra costs associated with these haracteristics and they can significantly reduce production risks.

 

Occasionally, you will need to compromise product characteristics. Remember, there are no perfect hybrids or varieties. Your goal is to find the best combination of desirable characteristics to fit your needs. Your seed suppliers should be able to assist you in this process. If not, look elsewhere. Be leery of hybrids and varieties that are promoted as “work everywhere” products. Once again, there are no perfect hybrids or varieties.

  

Finally, balance your ratio of “race horse” and “work horse” products. By that, we mean to use G x E x M to assess how hybrids and varieties react to different environmental conditions. Hybrids and varieties with a large G x E x M have more variation in performance across environments compared to products with a small G x E x M. In general, “race horse” hybrids and varieties have a larger G x E x M than “work horse” products. They do very well when conditions are optimal, but may perform poorly when conditions are tough. “Work horse” products, on the other hand, do not vary greatly across environments. They are classified as consistent and stable, and, in fact, have a low G x E x M.

 

For best overall results, it’s best to have a mix of both types of hybrids. “Race horse” products should provide the biggest return when conditions are optimal and planted on your better producing soils. “Work horse” products should be best when conditions are less favorable. Invest in both and build a balanced portfolio of products for your farm.