Tropicals & Tender Perennials: Hybridizing basics, 1 by EricKnight

EricKnight wrote:
F1 generation is the result of two parents of differing backgrounds. An example would be Rothkirch x Goldenes Kornett. The purpose of the F1 generation is to grow enough seedlings to produce a large F2 population sufficient in numbers to provide for meaningful selection. Example of F2 would be #27(Rothkirch x GK) x 42 (Rothkirch x Goldenes Kornett). The numbers here could signify the order in which they bloomed or some other criteria. A good base line F2 population (2,000-5000 seedlings).

(Goldenes Kornett x Rothkirch) = F1 (minimum grow out for mixed colors150-200) [Pink x Pink minimum grow out 50-100]

F2 = 25(GKxR) x 125(GKxR)
F2 = 125(GK x R) x 25(GKxR)
F2 = 137 (GK x R) x 25 (GKxR)

The idea behind your F2 crosses above is to have enough F2 seedlings going enough seedlings to make a meaningful selection. 2000-5000 being a good number to shoot for.

Now, there are still hybridizers who only want to select for one or two traits and can get by with less in the way of seedlings. However, take that advice with a note of caution: Think how many times Rothkirch has been crossed to Ocre to produce a myriad of named seedlings over the years. This is a simple F1 cross. Ecuador Pink x Rothkirch or Rothkirch x Ecuador Pink...another F1 cross. I think we have made it far enough that F1 crosses will not suffice for much longer with the exception perhaps of pure species x pure species F1 crosses like perhaps Goldenes Kornett (pure aurea wild) x Wild Versicolor Yellow.... I mean there is a chance here that besides hybrid vigor attained one may also get a double yellow or even orange out of such a cross. Still, you have to grow enough of that F1 to select out for the best. The earlier you start selecting the more you are inadvertently selecting against. Now, my math may be a bit off, but if you wanted to do a simple backcross for 4 generations you would get something that was 15/16 as pure as the original parent that you were breeding back to. What is the purpose here? It allows you to select for the genes and traits you desire or add them while attempting to purify your Brugmansia. Now, for others who are more inclined to the impossible, there is a wide world of experimentation that has been done with Brugmansia as well as Datura. If you simply look at the potato and how the cut style approach combined with a bit of agar utilized as a replacement for the style to allow the pollen to travel down and into the ovary.... . Now to get off topic even more...grafted seedlings can bypass the juvenile state that is associated with associated with seedlings when they are grafted onto mature specimens. Take this a bit further and some species become more susceptible to foreign pollens when they are grafted onto the plant to which you would like to cross them....there is tons more out there on the subject for those who like to read:
InVitro Plant Breeding by Acram Taji
Principles of Plant Genetics and Breeding by George Acquaah