Table 1.
Sixteen commercially successful varieties from the past 100 years in the USA were used in this experiment
Year of release represents the prominent agronomic background in which the varieties were successful, while the breeding method is another important distinction.
| Era | Release | Breeding method |
|---|---|---|
| 1 | Pre-1900 | Open pollinated variety |
| 1 | 1934 | Three-way cross |
| 1 | 1936 | Four-way cross |
| 1 | 1941 | Four-way cross |
| 2 | 1946 | Four-way cross |
| 2 | 1952 | Four-way cross |
| 2 | 1953 | Four-way cross |
| 2 | 1954 | Four-way cross |
| 3 | 1982 | Single cross |
| 3 | 1991 | Single cross |
| 3 | 1999 | Single cross |
| 3 | 2002 | Single cross |
| 4 | 2006 | Single cross |
| 4 | 2008 | Single cross |
| 4 | 2008 | Single cross |
| 4 | 2011 | Single cross |