Theories on Hybrid Plants

Plant Domestication

• The first evidence of plant domestication dates to 9,000 B.C. and was found in the region around the Tigris River. Over the next 8,000 years, as humans moved away from nomadic, gathering-hunting lifestyles and into agricultural communities, plant breeding continued to evolve. By 3,000 B.C., all food crops in the Old World were domesticated and 2,000 years later residents of the New World followed suit. By 700 B.C., the Assyrians were hand-pollinating dates.

Early Hybridization Theories and Experiments

• The Dutch created the first hybrid hyacinth in the mid-1600s. By the time Mendel came along, the groundwork for plant hybrid theories had been well-established by scientists such as Camerarius, who theorized about systematic breeding practices in 1694; Fairchild, who created hybrid flowers in 1719; and the groundbreaking 1753 work of Linnaeus, who developed taxonomy based on binomial nomenclature. Other early theorists included Koelreuter, who established that hybrids display genetic traits from both parents, and Herbert and Knight, who theorized that hybridization could be used to produce plants with superior or desirable traits, such as cold hardiness.

19th Century

• In 1801, Lamarck advanced the theory that species inherit acquired characteristics. For instance, a flower with a stronger scent may attract more bees, which results in more pollination -- and more offspring that also have a stronger scent. Von Gartner took scientific hybridization to new levels, creating 10,000 hybrids using 700 parent species. In the 1830s, Red May and Hovey advanced the economic impact of crop plant hybrids by creating commercially viable wheat and strawberry hybrids. Schleiden and Schwann developed their cell theory based on the assumption of plants as “autonomous vital units” consisting of small groups of cells, and that more complex plants consist of collections of these cell groups. In 1858, Darwin and Wallace established the theory of natural selection, setting the groundwork for later theory.

20th Century and Beyond

• Mainstream science finally accepted Mendel’s work in 1901, a development closely followed by DeVries’ development of the mutation theory of evolution, which assumes that single mutations can create new species. Bruce, Keeble and Pellew developed a hybridization theory proposing that dominant genes result in hybrid vigor. In 1920, Jones theorized that commercial cultivars of plants could be created through a four-way hybridization process. In 1944, Avery, MacLeod and McCarty theorized that hereditary traits are passed through DNA rather than in protein, as was previously believed. More DNA theories led to the discovery of hybridization techniques such as the creation of high-yield, dwarf food crops, which had a significant impact on agricultural practices around the world. Today, the culmination of these theories is reflected in the production of hybridized food crops that use the process of introgression, or hybridization between a domesticated crop and a related wild species; heterosis, or hybrid vigor crops; and other genetic modification techniques that are grounded in the theories that came before.