Into the fray:
Breeding with feminized seeds
By: Paul Josephs
Feminized seeds — it’s hard to think of a topic that has as much of a flashpoint effect as this one. What are feminized seeds and plants? Can and should they be used in breeding? Before addressing these questions, in the interest of transparency, I wish to state that I do not work for, endorse, or have any bias toward any authors, seed brokers or breeders. I have absolutely no agenda or vested interest in this subject, other than seeking truth and realism. So let’s dive in, shall we?
What are feminized seeds?
Cannabis owes its generous genetic variability to many strains being dioecious. As such, populations grown from non-feminized seeds usually contain a roughly equal percentage of plants that are either male or female. Monoecious Cannabis strains also exist and have male and female flowers on the same plant which are often used in hemp production crops. It is the female plants from dioecious strain populations that are valued by recreational and medicinal users, and the males are invaluable to breeders for facilitating genetic recombination when they pollinate female flowers. Not everyone wants male plants, however, especially growers who only want females to harvest. There are a number of methods to get a female plant to generate seeds which only produce female plants if grown in ideal conditions. These seeds are referred to as feminized seeds.
How are feminized seeds produced?
There are several methods that breeders can utilize to produce seeds that are all female. All of these methods involve using pollen produced from stamens that appear on female plants. This pollen only has the female sex chromosome X and, when used to pollinate itself, or another normally female plant, will produce seeds that only have the female sex chromosome combination XX. Naturally occurring male plants have the XY chromosome combination, and pollen from these males will either have the X or Y chromosome. Since the female sex cells all have X chromosomes, they will fuse with either X or Y sex cells from the male pollen — all resulting XX paired seeds will be females, and all XY paired seeds will be males. Below we will explore the three primary ways to induce male flowers on a female plant to have the X chromosome only.
Gibberellic acid: This chemical compound in dilute form applied to female plants will often induce male stamens to be generated. This pollen will be exclusively X-bearing pollen.
Silver thiosulfate: Another compound that has the same effect of inducing male stamens on an otherwise female plant, with the same result of producing exclusive X-bearing pollen.
Stress: A flowering female plant will sometimes produce some male flowers when it is subjected to environmental stressors, allowing for an organic method of creating all genetically female seeds. Varying the photoperiod to be random or switching from flowering to vegetative cycles frequently, heat stress, nutrient deficiencies and other stressors can cause the production of male flowers on a predominantly female plant. It is important to note that the degree of ease with which a plant responds to such pressures is likely to be passed on to future offspring.
Cannabis is a genetically variable genus that has a range of sex characteristics. Monoecious strains have large numbers of male and female flowers on the same plant. Hermaphrodites are male or female plants that exhibit some flowers of the opposite sex. The difference between a monoecious strain and a hermaphrodite strain is a matter of deciding where in that spectrum to make the delineation. Some strains rarely exhibit mixed-sex flowers and in others they can be common. Naturally occurring hermaphrodite traits are inherited and naturally occurring hermaphrodites should not be used as a feminized seed crop parent. Robert Clarke, in his book, Marijuana Botany, makes it clear that selfing a hermaphrodite will usually give rise to hermaphrodite progeny. Clarke also points out that putting pollen from induced staminate flowers onto a naturally occurring female plant will generate almost exclusively (emphasis added) female producing seeds if used on a normally female parent.
Can you breed with feminized seeds?
Yes. Feminized seeds do not produce sterile plants, but rather have been manipulated using the pollen from a ‘reversed’ female to produce exclusively or almost exclusively female seeds. A feminized seed almost always grows into a female plant, keeping in mind that environmental stress may trigger a plant to exhibit male flowers. If you have a spectacular plant from feminized seed, you can breed it by crossing with a male and the resulting progeny will have genes from both parents.
Should you breed with feminized seeds?
The common concern is the hermaphrodite issue. Let’s see what some respected opinions are on the subject.
In a Cannabis Culture article Ed Rosenthal states that when breeding feminized plants there is the possibility that one could be inadvertently selecting for hermaphroditic traits and that this tendency may take a few generations to manifest.
Greg Green in his book, The Cannabis Breeder’s Bible, relates his opinion that breeding with feminized seeds is not preferable to using standard seeds since they exhibit a tendency for hermaphroditic traits if the plants are stressed. Green goes on to take the more direct stance that feminized seeds should be used for growing purposes only and not for breeding.
The Rev gives his opinion in his True Living Organics book that feminized seeds should be avoided for breeding, citing concerns about selfed plants and bottlenecked genetics, though he does not directly address hermaphroditic plants.
The hermaphrodite issue is a valid concern, clearly. Nobody wants to increase the chance of male pistils appearing on their otherwise female flowers. If a plant is easily stressed into reversing and is used to make feminized seeds, it follows that the offspring are going to carry that trait of readily exhibiting hermaphroditism. This is clearly not a desirable breeding trait. However, there is a continuous spectrum between that example and the case of a female that simply can’t be stressed into reversing by environmental means other than chemically with gibberellic acid or silver thiosulfate. Are the feminized seeds from the latter example going to grow into females that are easily stressed into exhibiting hermaphroditism? My personal opinion is no, not any more than if that same plant was not reversed and crossed with a normal male and its female offspring were stressed. Depending on the male genetics, there might be more hermaphrodites seen in the normal females than the feminized ones.
Wrapping it up
Feminized seeds pose a problematic choice for a breeder. Depending on the plant being reversed, they present a variable range of risk of hermaphroditic expression. It must be noted that regular seeds are also not immune to this range of risk. A good breeding program involves researching and observing and making crosses accordingly. If the genes for an undesirable trait exist in the genotype, inbreeding can concentrate that trait and it may be expressed more frequently with subsequent generations. Making a poor choice of parents can be made just as easily with regular seed grown plants as feminized ones.
If you are confident that the plant reversed was a type that is very hard to reverse, it shouldn’t present a bigger risk than using regular seed. This is very important. The authors referenced in this article have a legitimate point. It is imperative to get a straight answer from the breeder as to how the feminized parent was chosen. If it was just based on the phenotype and the plant was not subjected to a battery of stress tests to see how easily it shows hermaphroditism, it may well be risky to breed with. Feminized seeds are not going away — they have great importance to growers who simply want female plants to invest their money and time into growing. Feminized seeds are a lot of work to produce by the breeder — if not then the plant was easily reversed and so its offspring be disposed to be as well — and for this reason they cost more. Seed breeders are going to supply what the customers demand, and there is a large demand for feminized seeds. It is incumbent upon people who plan to breed with these feminized plants to do so with as much knowledge as possible about what they are working with so they can gauge the potential downside accordingly.
If I had a male of a line that I felt needed a genetic infusion from a certain strain that is only offered as feminized, and I had good reason to believe that the breeder used a reversed plant that was virtually stress-proof, I would breed with it. I also would keep a close eye on the progeny and stress-test every generation — which is good to do with any breeding program regardless of what type of seeds you begin with.