Carefree Sunshine often produces blackspot-free seedlings.
Compassion also often produces bs free seedlings.
What modern varieties do you use to get bs resistance in seedlings?
Dave did you use Carefree Sunshine as a seed or pollen parent?
CS works both ways, but best results have been as pollinator: Distant Drums x CS; April Moon x CS; Julia Child x CS; in all these cases, seedlings have been much cleaner than seed parent.
I suspect that Carefree Sunshine is a triploid as I found a pollen diameter of 37.7 microns, with a standard deviation of 3.9.
If you use your search function for Carefree Sunshine in my spreadsheet linked to below, you will see what crosses I have with Carefree Sunshine.
Link: spreadsheets.google.com/ccc?key=pxHhTw7ylg7-ZLZEfJr4eEw&hl=en
Hi Henry,
I confirmed Carefree Sunshine as a tetraploid. In the Spring 2004 newsletter I believe I wrote about the chromosome counting technique I use and there was a photo of a root tip cell from Carefree Sunshine showing its chromosomes. There can be a lot of variability in fertility among tetraploids, as roses at any ploidy level. Time of year and growing conditions can influence fertility too. Modern roses have so much in their background that it can be difficult for chromosomes to always recognize each other and pair consistently and lead to balanced gametes. Unbalanced or aneuploid (incomplete sets) often have reduced viability and greater variability, especially common in pollen from triploids. There are many factors that ultimately impact fertility.
I have some rooted cuttings of Cuthbert Grant and look forward to counting its chromosomes. I remember you mentioned Henry that it has reduced fertility from your observations of its pollen. It’ll be interesting if it is triploid, some of the other Morden roses are like Prairie Joy.
Sincerely,
David
David,
It is my understanding that roots can have a different chromosome number than the other parts of the plant. I do not know how common this is.
http://www.sciencemag.org/cgi/content/abstract/168/3935/1115
Henry
I was visiting with Walter Lewis about this. It would probably be very rare in roses, but many things are possible. There may be periclinal chimeras with different layers of the meristem perpetuating different cells at different chromosome numbers. Leen Leus describes a few among the roses she surveyed with flow cytometry. I assess Layer III typically because I am using root tip cells and adventitious roots from cuttings typically come from within cells in the stem from layer III. Squashed shoot tips should be able to give us cells from each maintained meristem layer and hopefully see the differences in chromosome counts across cells.
Pollen is derrived from LayerII tissue and from looking at some ploidy and ploidy conversion literature in potatoes and I suppose we can build a case for roses too that Layer II and Layer III typically are more closely associated and cells can cross between the two more readily and Layer I tends to stay more distinct from the other two. Perhaps it’s because Layer I has a slightly different way of dividing initially (more outward in a single layer to make the epidermis tissue).
When I sampled Carefree Sunshine I got 42.7