Most people new to Clivia breeding will have heard the term F1 or F2 with regard to crosses between plants or seen one of these terms on the label of a plant, and scratched their head as to the meaning of this strange term.
Often, an assumption is made as to the meaning of the terms and the terminology is then used in further breeding efforts. In many cases, these terms were incorrectly used originally and then the incorrect use is further propagated. Eventually the result is confusion regarding the breeding of a plant, particularly when the plant is sold to a novice.
‘P’ generation In 1856, Johan Gregor Mendel (1822 – 1884) began a decade-long research experiment to investigate inheritance using garden peas. True breeding parents, he referred to as the ‘P’ generation for parental generation. He crossed two plants from the ‘P’ generation and documented the different characteristics and colours in the parental generation as well as subsequent generations.
F1 generation F is short for the Latin word filia which translates as daughter or son. F1 or F1 refers to the first filial generation which is the offspring from the initial cross between two parent plants (‘P’ generation).
Mendel discovered that the F1 generation displays the dominant features from the two parent plants rather than a merging of traits, which was the common thought at the time. In further generations, hidden features appeared in a percentage of plants. Mendel coined these the ‘dominant’ traits and the ‘recessive’ traits. In 2009 the Melbourne Clivia Group first published an article by Helen Marriott titled, An introduction to interspecific hybrids, revised in 2018, where Marriott discusses the thoughts of well-known growers. In the remainder of this article, there will be relevant texts quoted from that material.
To maximize the potential of interspecifics, the breeding of more than one generation is necessary. Rudo Lotter, for example, argues that in a first generation cross (F1), such as crossing C. miniata x C. gardenii, the siblings will not exhibit a lot of variation. To bring out further characteristics that are recessive, the best F1 siblings are crossed between themselves (or selfed) to create the F2 generation. (Marriott, 2009)
F1 does not apply to a plant that has been selfed. A plant that has been selfed is not a cross between two genetically distinct plants and therefore, this terminology does not apply. This is important as my own observation is that in the Clivia world, growers use the term F1 after the plant’s name to identify that the plant has been selfed. I have seen this countless times all over the world and it has become the norm to call a selfed plant, an F1. I have been guilty of doing the same for years as I accepted that this was what F1 meant. A quick review of the Facebook Clivia Groups reveals many photos of plants simply referred to by a name followed by F1. The assumption is that the photo is a selfed plant.
F2 generation F2 or F2 refers to the second generation. If F1 was the daughter, then F2 is the granddaughter. This may be the crossing of two siblings of the F1 generation, or it may be the selfing of one of the F1 seedlings. Mendel allowed his F1 generation to naturally self-fertilise to produce the F2 generation. The F2 generation may be the crossing of F1 siblings, or the selfing of an F1 seedling. In the F2 generation, desirable recessive traits may be apparent.
Note that if an F1 interspecific (or any other F1 for that matter) is subsequently used in a cross with a different parent, it becomes a new F1. (Marriott, 2009) Yoshikazu Nakamura’s experience is that excellent interspecfic hybrids can be achieved already by the second generation (F2). He has often selfed his F1 interspecific hybrids, thereby bringing out many attractive features in the flowers of the F2 generation. (Marriott, 2009)
It is not correct to assume that F2 refers to a plant has been selfed, and then selfed again. For example, (Vico Yellow x self) x self. This has been used commonly in the Clivia world, and I have also heard of people referring to a parent plant that has been selfed as an F2 generation. This is also incorrect and confuses the novice purchasing a plant with the label, Vico Yellow F2.
What is the breeding of this plant? Is it Vico Yellow x self? Is it (Vico Yellow x self) x self? Is it (Vico Yellow x Something) x (Vico Yellow x Something)? Is it (Vico Yellow x Something) x self?
Although it has been suggested that we only need to proceed to the second generation (F2) in interspecific hybridisation, Keith Hammett indicates that quite often, recessive traits are not expressed until generations much later than the F2 (personal communication), so there may in fact be reason to proceed to F3 or F4 though sibling crosses or selfing. (Marriott, 2009)
Conclusion If unsure what the F1 or F2 term denotes when purchasing a plant or seed, it is best to ask for specifics on the cross. If you plan to breed further with the plant, then knowing the exact parentage can save time and effort and make a difference with a breeding program. With my own crosses, I now only write the correct cross and no longer use the F1, F2 and F3 terminology on labels. I reserve these terms for my own records. It saves confusion for all involved.
References Hyatt, D. (2004). What’s the difference between F1 and F2? Virginia, Journal American Rhododendron Society Wikipedia, (2004). F1 hybrid.[online] Available at: https://en.wikipedia.org/wiki/F1_fusion [Accessed 2 Oct. 2020] GKVK, (2018). F1 F2 F3 Hybrid Seeds and Pollination | Seed Saving Basics. [online] Available at: https://www.gkvks.com/f1-f2-f3-hybrid-seeds-and-pollination-seed-saving-basics/ [Accessed 2 Oct 2020] OpenStax, Biology. OpenStax CNX. May 14, 2015 http://cnx.org/contents/185cbf87-c72e-48f5-b51e-f14f21b5eabd@9.85
