Done a few decennies ago by a french scientific team now gone and materials plants and seedling from I do not know the destination.
Or Google “dihaploid roses”
Dihaploids from our tetraploid roses are great tools for further research. In the past I shared about the dihaploids I got from normal observation. They are produced in nature at low frequencies as a means for roses to go up and down in ploidy, just like there is low rate of unreduced or 2n pollen to go up in ploidy. The most adapted ploidy levels for fertility, growth, etc. have a way to be generated and persist.
I have obtained dihaploids of Rise 'N Shine and Dorcas. Unfortunately, the two from Dorcas died. Most were identified as twin embryos sharing a common testa and the smaller embryo being a synergid likely (same genetic constitution as the unfertilized egg) that developed into an embryo. They are weaker generally and a bit smaller than typical seedlings if they even make it. Generally in breeding programs they would not be selected. In addition, I found one from a cross that should have produced one time blooming seedlings (Rise 'N Shine x 4x species). One seedling was repeat blooming and after counting it, it was diploid.
We can sort through these for those that are vigorous enough and fertile enough to use for breeding with other diploids, for crosses to get more manageable segregation ratios for genes to learn how traits are inherited, etc.
It was very cleaver for the French group to use irradiated pollen and embryo culture to rescue unfertilized eggs stimulated to start developing into embryos. Henry Kuska tried anther culture as well as others and were unsuccessful in generating dihaploids from pollen grains. I tried too and learned silver nitrate helps avoid browning of callus that formed.
Crosses of our modern triploids with each other or diploids can lead to some 2x hybrids too. I have a diploid seedling of Rainbow Knock Out. So, there are multiple ways we can get to the diploid level if we want to.
"We can sort through these for those that are vigorous enough and fertile enough to use for breeding with other diploids, for crosses to get more manageable segregation ratios for genes to learn how traits are inherited, etc. "
That was what the french team was doing precisely when dissolved.
Many dihaps were strong and fertile enough under greenhouse environment.
From full size florist HT roses the dihaps were thinner stemmed and foliaged about patio size. Souple and dense.
Stiffness we collectively and inconsciously are breeding for was gone completely.
Fascinating little plants that are probably lost as being from a subsidized program, resulting plants were not shared.
A fact that was shared is that progenies partly had unexpectable ploidy. They hypothetized it could be from “cytoplasm induced” unreduced gametes.
Someone to experiment diploid species/var based rose breeding?
Caffeine, uracil and sodium nucleate have been used to induce somatic meiosis in some plants.
http://bulbnrose.x10.mx/Heredity/King/Chemicals.html
1 Like