9: Multilines and Seed Blends

Introduction

This chapter discusses the reason for multilines or seed blends and the methods that can be used to make commercial multilines or seed blends. You will investigate further the commercial uses of seed blends by completing the Applied Learning Activity at the end of this section.

For seed blends of multiple plant species or multiple genotypes of a species, the components used are those best suited for the intended purpose. For example, a seed blend of Kentucky bluegrass and ryegrass for planting a lawn will involve mixing seed of the best clonal cultivars of Kentucky bluegrass and the best synthetic cultivars of ryegrass for the geographical region of interest. Breeders generally do not breed cultivars specifically for use in a blend. Instead, cultivars are developed to be used individually. The same cultivars can be used in a seed blend. For example, a company may sell a single synthetic cultivar of alfalfa to some farmers or blend the cultivar with a synthetic cultivar of bromegrass to sell to other farmers.

The most recent use of seed blends is in maize for the concept referred to as refuge-in-a-bag that you will investigate as part of the Applied Learning Activity. The articles available to the public do not describe the origin of the transgenic and non-transgenic hybrids that are blended together. According to industry sources, seed companies first develop inbreds for use in non-transgenic hybrids. The transgenes are backcrossed into the inbreds of a hybrid. Since multiple transgenes are used for insect resistance, some of them can be incorporated in one inbred and others can be incorporated into the other inbred. The inbreds with the transgene derived from the backcross will be near-isogenic lines of the original inbred. Therefore, inbred plants with the transgene should be the same phenotypically as the plants without the transgene. Similarly, the hybrids with and without the transgenes should be phenotypically the same. As a result, a farmer will not be able to see a difference between hybrid plants with or without the transgene, unless the plants without the transgene show symptoms of insect damage.

To make the seed blend sold to farmers for the refuge-in-a-bag, hybrid seed is produced independently with and without the transgenes. After the seed of each is conditioned, it is mixed in the proportion desired by the company.

1. Visit the website for the Warner Brothers Seed Company. What is the rationale for the blends of different species that they are selling?
2. A seed blend is used in corn hybrids that contain transgenes for insect resistance. Visit the archived website at Farm Industry News regarding single bag refuge seed. What is the rationale for the use of refuge-in-a-bag, instead of the previous requirement of planting a separate refuge in a field of corn?

References

Bailey Seed Company. “Pasture Grasses.” Accessed January 25, 2025, http://baileyseed.com/resources/pasture-grasses/

Farm Industry News. 2011, May 11. “Single-bag refuge seed sold this season.” Accessed January 25, 2025, https://web.archive.org/web/20140904...ed-sold-season

Fehr, W. R. (ed). 1987. Principles of Cultivar Development. Vol 1. Theory and Technique. McGraw-Hill, Inc., New York.

“Warner Brothers Seed Company.” Accessed January 25, 2025, https://www.wbseedco.com/