BEYOND THE HIVE
How Nativars are Cultivated If there is a subtle difference between a nativar and a cultivar, it lies within the number of manipulations the plant has undergone. Certain cultivars of vegetables and garden one removing the plant further from its wild progenitor. Many modern fruits and vegetables are hybrids that don’t have so many rows of petals that pollinators cannot even Most nativars on the other hand—at least for now— are closer to the original plant, having undergone fewer selections and crosses. Some nativars are not hybrids and remain open-pollinated, seed-producing plants. Bear in mind, however, that the number of selections and crosses that go into creating a nativar is up to the breeder, there is no standard or maximum number. It’s a trade secret. Cultivars, including nativars, can be produced in
several ways:
Selective breeding—the kind I used in alfalfa—is a common source of new cultivars. To breed selectively, a grower chooses individual plants that display the desired trait and then crosses them with each other. This type of cross has the effect of increasing the frequency of the desired gene in a population while still maintaining a fertile, openly pollinated population. For example, a breeder may search his crop for the tallest individuals, and then cross these with each other. The offspring of this cross are likely to be taller on average than the original crop.
Hybridization is more complex than simple selective breeding. To hybridize, breeders take genetically dissimilar individuals and cross them, producing offspring that are different from either parent. The resultant plants may be fertile or not, but the offspring of a hybrid are unlike the parents. Because the offspring are so different, the hybrid is usually cloned by vegetative reproduction, such as cuttings or tissue culture. When you look at a plant label, a hybridized plant usually
lists the genus name without a species name followed by an X, and then the cultivar name in single quotes. This indicates two species were crossed, and the offspring belongs to neither one. The X is simply shorthand for “cross.”
Backcrossing hybrid (F1 generation) with one of its parents. It is used to produce a plant that is more similar to the original parent than the F1 hybrid, while still maintaining the desired trait created in the hybrid. From a practical point of view, backcrossing can cause a substantial loss of genetic diversity even though the offspring appear similar to the parent.
Above: A mutation caused this tulip to be bicolored. Breeders sometimes find natural mutants and then breed offspring to select for this unusual color trait. Below: Breeders often select for colorful leaves, which can change the palatability for caterpillars.
Mutagenesis, also called mutation breeding, is a process of introducing mutations into the seeds of a plant to see what results. Although mutations can occur spontaneously in nature, laboratory mutagenesis usually involves exposing seeds to chemicals or radiation to alter the DNA. These seeds are then grown in controlled conditions, and any changes in the offspring are examined for their usefulness. Many of today’s food crops resulted from radiation treatments, grapefruit, peanuts, rice, wheat, and peppermint.
Selections from the wild stock can also become a source of cultivars. In its simplest form, a breeder searches for a plant with particular traits from wild stock he is cultivating. When or tissue culture.
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