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What is Plant Breeding?
Plant breeding is the science of crossing two plants with the goal of selecting specific phenotypes from the offspring. This manipulation involves controlled pollination or open pollination. Controlled pollination is the method of harvesting male flowers and using a tool, such as a paint brush to deliver pollen directly to specific female flowers. This is a great method for breeding multiple male plants to a single female plant, care should be taken in order to know which males were dusted onto each branch. Open pollination involves allowing a male plant to flower in a room full of females. In this manner, all of the females dusted with pollen will likely be seeded. This is a great method for crossing a single male with many different female varieties.
Plants are crossbred in order to introduce traits from one variety into a new genetic background. For example, one variety may have a wonderful aroma and distinct flavor, while having a lower than average yield. Another variety may have a higher than average yield while not having a characteristically strong flavor. The goal of the cross being to introduce the flavors and aromas without losing the high-yield characteristics.
The resulting seeds would be considered F1 hybrids, meaning they are the first filial generation of this cross. If a candidate from these seeds is selected and shows the desired combination of characteristics, further breeding can then be done in order to stabilize and further enhance these traits.
F1 & F2 Hybrids
F1 hybrids are generally more vigorous than the individual parents crossed to create them. This is called hybrid vigor. The resulting seeds also show little phenotypic variance from seed to seed, showing a general dominant trait among all seeds planted. It is when two seeds from a F1 hybrid are bred together that a very large variation will be seen amongst offspring. This is called an F2 hybrid. From here a combination of backcrossing the F2 with parental lineage and inbreeding to selected brothers, sisters and cousins is used in order to select the desired plant characteristics. Backcrossing and inbreeding should be done with care, and not with too much zeal. As is it common-place for weak, recessive traits to begin showing themselves, making for unexpected mutants and sometimes poor performing plants. If a plants’ genetics begin to weaken then a new line of genetics should be brought in to once again hybridize and reinvigorate it.
Also possible is the reversal method. Using a foliar spray such as Tiresia’s Mist it is possible to reverse a female plant and create male flowers in order to pollinate itself, as well as other nearby plants. The seeds that are produced by this method are generally all female. Known as feminized seeds, they are a convenient solution for those trying to guarantee a certain number of females in a group of seedlings. This is a great way to preserve and breed out “clone only” varieties, expanding on unique genetics and furthering the availability of sought after varieties.