R. wichurana hybrids for disease resistance.

This is intended as a spin-off thread from David Zlesak’s conference abstracts post earlier today.

In the past decade I have found that many of the R. wichurana hybrids I grow are extremely resistant to Blackspot. Some cultivars are immune to it, in fact. My work with some of the R. wichurana primary hybrids suggests that superior Blackspot resistance is passed on fairly often. I feel that some of these R. wichurana hybrids are potentially a better avenue for the search for disease immunity than the ‘Knockout’ line of breeding, which appears to be limited to breeding lookalikes and lots of single blooms. R. wichurana has two other advantages: it can breed a variety of bloom forms and styles, and it often imparts the ability to propagate from cuttings with great ease. Oh, and it often passes on a variety of very pleasant fragrances.

In 1988 Ralph Moore introduced ‘Ralph’s Creeper’, an attractive weeping style shrub with medium red flowers and in many climates, superior disease resistance. Its parentage is ‘Papoose’ X ‘Playboy’, the seed parent being a first generation R. wichurana hybrid.

‘Papoose’ is a cross of R. wichurana X (‘Carolyn Dean’ X ‘Tom Thumb’). It looks very much like R. wichurana but is more compact, rarely exceeding a 6 foot diameter spread and not over 15" tall. Blooms are single white, and there is some repeat through the season when it matures. Its not easy to get it to accept pollen, but it can be done. It has better pollen fertility. In my climate it is 100% immune to all diseases. I’ve neglected it for a few years because it was difficult to get seed from, but I will be returning to it this year, more as a pollen parent.

I have just dug up and potted some pieces that had formed as rooted tips and I will offer these to anyone who wants to work with it. I just potted these so I expect it will be 6 weeks before these can be safely shipped. Email me if you want a piece of ‘Papoose’.

Paul

Link: www.helpmefind.com/rose/pl.php?n=15722&tab=1

Hi,

I would be interested in Papoose but dont have access to your email address.

-Steve

Steve,

Click on the email link to the right of my name at the head of the post. :slight_smile:

I have been reluctant to do a lot with R. wichurana mainly because it appears that so much work has already been done with it.

I agree that its not exactly “unexplored territory” Henry, but I do feel that it hasn’t been explored sufficiently as a source of disease resistance. I think some of these lines have more to offer than they have so far. A few generations of careful line breeding could develop some superior breeders that can be used by people down the line, in the same way that cultivars like L83 are being used now.

Paul

Ha, yes I tried it. Wasnt working when the first time. I can never remember if the email feature is working or has been disabled. As is typical, it working when I just clicked on it a minute ago. :slight_smile:

I have no more space for non-remontant cultivars but please let me know if you get a remontant diploid first generation descendant. Thanks, Robert

A lot of the wichuraiana hybrids grow well around here in Australia but are not especially black spot resistant… especially at the beginning of the season. They are also prone to cercospora more so than other roses in my garden. A lot of Mr Moore’s miniatures come from wichuraiana (like Green Ice) and while they are good growers they seem to get BS bad here at certain tmes of the year. Add to this roses from the Flower Carpet series and Bassino roses which are strong growers but develop plenty of BS. My own best seedling to date from Green Ice shows plenty of wichuraiana influence and gets a good dose at the beginning of the season like every other wichuraiana hybrid I have (including the species wichuraiana I have) and then grows cleanly for the rest of the season until the end of the season when it older leaves start to show it again (not a big issue IMO because they are old leaves at the end of the season and they’ll be dropping off soon anyway). Maybe we have a different strain of BS here. It doesn’t get as hot here as the rest of Austrlia so it isn’t a heat thing.

I’m sure its a matter of differing strains of Blackspot. Sadly we can’t test for all of the strains, because while the cultivars we grow remain genetically static, the diseases evolve. However, there is hope, since many of the North American native species are quite disease free.

Thanks for posting this Paul. Of the Wichuriana hybrids, I have the most experience with New Dawn. It is entirely disease free for me. It is also disease free at many botanical gardens in the area. That is pretty remarkable considering how long it has been around. I think a lot more could be done with Wichuriana hybrids.

Many/most of the Brownell roses were based on Wichuriana blood(sap?).

Link: www.rirs.org/drbrownelldorrienichols.htm

Thanks for the link to the Brownell article Henry. I enjoyed it. Those certainly were innocent times and great times to breeding roses. It’s amazing how much Brownell’s work still impacts us today.

For those who want to use an easy seed parent derived from New Dawn, ‘Armada’ fits the profile. I have no idea how cold hardy it is. It will get a tiny bit of mildew here in some years but I did get some (so far) completely mildew free banksia derivatives from it. Most seedlings will be pink or white in the first generation.

I did get yellow out of it in the second generation.

I have one plant of New Dawn, and two of its super-double sport, Awakening. New Dawn and one of the Awakenings are separated by about 6 feet. The second Awakening is about 50 feet away. I sometimes see a light black spot infection on some of these. Last year, the isolated Awakening had none, while the other 2 had a light infection.

Personally, I sometimes think that a light infection is better than no infection. No infection may mean vertical, single-gene resistance, which is easily overcome by: 1) mutation in the pathogen, or 2) movement of plant or pathogen so that the plant is exposed to new races (strains, forms) of the pathogen.

The breakdown of Baby Love

Does that make me Homo sapiens sapiens, Strain: Cracker? lol

For what it is worth, I still think Baby Love has a lot of breeding value. Then again, I think a lot of roses do.

Theoretically, if two roses have lost their resistance due to different strains of black spot, crossing them could produce offspring resistant to both. Vertical resistance is dominant, and only one copy of the relevant allele is needed. The number of resistance alleles a cultivar can have is not limited to two. David has suggested that this may be Knockout