My rose breeding mentor, Elton Strack, tried it in the late 1980’s. I don’t think it was very successful for him. In lilies I’ve used it to generate wide intersectional crosses. Subsequently, I rescued the embryos before the endosperm failed and matured them in tissue culture. I also generated some selfs in Easter Lily this way as well.
The main purpose of cutting the style is to reduce the length the pollen tube has to go. With cut styles and lilies at least the pollen tubes don’t grow normally and tend to twist a lot, so if you have a cross where it is not necessary to use the cut style technique it is better not to do it.
For roses it might be helpful to get around self-incompatibility and may aid in some wide crosses. It seems very meticulous and one would need to be very careful to not let the cut surface dry out while the pollen is germinating and the pollen tubes are starting down the remainder of the style. With lilies there is a lot of stigmatic exudate produced, so I place some on the cut surface before pollination to aid pollen germination. With roses the quantity of exudate is much less relative to lily. Perhaps one can drop some solution like I reported for hanging drop pollen germination assays (.75% sucrose 40ppm boric acid) in a recent RHA article onto the surface to help stimulate pollen germination.
Another approach is to use heat. 100F in lilies can breakdown the self-incompatibility proteins in the style and allow for selfs as well as wider crosses. In roses in a hot greenhouse in summer I can get some selfs on some normally self-incompatible roses. Perhaps heat can aid pollent tube growth, if indeed that is the limiting factor in the particular cross, with wider crosses in roses as well.
Thanks for the link and bringing up this topic on the forum Henry.
Interesting stuff! I’m wondering if high temperatures might have been involved in a cross I did, that I can’t get to repeat.
And after reading that Eucalyptus reference, I think I’ll have to play around some more with cut-style techniques.
I’m not sure heat would help with seed set of roses. I know when the sumer gets hot (80-100), seed set decreases. Unless there is some other factor involved?
Good point Joan. I think humidity and water relations comes into play as well. The main function of the heat for such a purpose is to inactivate, or reduce the activity of, incompatibility proteins in the style that can interfere with the developing pollen tubes. For heat to be beneficial such proteins would need to be the predominant factor limiting fertilization which would take some effort to truly determine. With lily at least, we are fortunate and can do things like heat the long style in warm water for a relatively short period (5-10 minutes) and then pollinate and allow things to continue just at room temperature. Roses would seem to be more tricky to this type of modification with. In that hot greenhouse where I had those roses that set some self seed (>100F each day) I was watering a lot. I did get seed, but the seeds per hip was less than from normal outcrosses outside. Heat probably had an effect on final seed set, but also less than usual seed per hip may be due part to inbreeding or heat not fully deactivating the proteins and a limited number of pollen tubes getting through.