Soybean, Glycine max (L), is an important and valuable field crop.  Thus, a continuing goal of soybean plant breeders is to develop stable, high yielding soybean varieties that are agronomically sound.  The reasons for this goal are obviously to maximize the amount of grain produced on the land used and to supply food for both animals and humans.  To accomplish this goal, the soybean breeder must select and develop soybean plants that have traits that result in superior varieties. 
Due to the environment, the complexity of the structure of genes and location of a gene in the genome, among other factors, it is difficult to predict the phenotypic expression of a particular genotype.  In addition, a plant breeder may only apply his skills on the phenotype and not, or in a very limited way, on the level of the genotype.  As a result, a particular plant breeder cannot breed the same variety twice using the same parents and the same methodology.  Thus, a newly bred variety is an unexpected result of the breeding process.  Indeed, each variety contains a unique combination of characteristics. 
By carefully choosing the breeding parents, the breeding and selection methods, the testing layout and testing locations, the breeder may breed a particular variety type.  In addition, a new variety may be tested in special comparative trials with other existing varieties in order to determine whether the new variety meets the required expectations.