A practical experiment can illustrate the above:
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One benefit to breeding for a recessive trait is that all of those that autoflower would have been true bred for autoflowering and can be bred together to make more autoflowering seeds. (Read Do my autoflowering weed seeds need additional nutrients?)
In this case, photodependancy is dominant, so the resulting Pp seeds will all be photodependant. This is why the first generation after crossing a true breeding standard plant with a autoflowering plant will create seeds that are photodependant and will not autoflower.
Step 1: Take a standard cannabis plant and cross it with an autoflowering variety. It doesn’t matter which supplies the pollen as long as one is male and the other female.
While technically there are four combinations possible, effectively it doesn’t make much difference because all of the combinations result in PP (true breeding for photodependancy). This is why breeding a standard cannabis plant with another standard cannabis plant will result in standard cannabis offspring. The same is true of autoflowering.
Of importance to breeders, both experienced and aspiring, autoflowering is an easily observable simple Mendelian recessive trait. It is generally quick and easy to determine if a given adolescent plant is autoflowering or standard just by keeping it in short (or non-existent) dark periods for a few weeks. If the plant stays in growth, it is standard. If it flowers it is autoflowering.
Cannabis normally requires long dark periods to trigger flowering, but there are varieties that will flower regardless of the lighting conditions. These are known as autoflowering varieties. Not all cannabis traits are as simple to explain, which is part of what makes autoflowering a good example for beginning breeders to start with.
Step 2: Grow out the resulting seeds. They should act as if they were standard seeds. Select the best male and at least one female and cross them together.
When it comes to breeding cannabis, autoflowering is one of the most basic types of genetic traits of the plant.