Taming The wild Ones

A meeting place for rose breeders.
roseseek
Posts: 5283
Joined: Sun Dec 11, 2011 6:54 pm
Location: Zone 9b Central California, Sunset Zone 15

Re: Taming The wild Ones

Post: # 73257Post roseseek
Thu Aug 26, 2021 12:30 pm

Banksiae seedlings and hybrids are notoriously mildewy. At least the straight seedlings out grow it and achieve the high degree of resistance it demonstrates. Not all hybrids do. Minutifolia seedlings are highly mildew susceptible but maturity appears to eliminate that pressure. So far, all of my modern X Minutifolia hybrids are resistant. Stellata mirifica X Minutifolia seedlings appear EXTREMELY mildew susceptible. Hopefully, they will mature out of it as neither species is affected.
Kim
California Central Coast
USDA Zone 9b
Sunset Zone 15
Cooler inland coastal valley with strong marine influence

Plazbo
Posts: 206
Joined: Tue May 09, 2017 12:18 am

Re: Taming The wild Ones

Post: # 73258Post Plazbo
Fri Aug 27, 2021 4:48 am

roseseek wrote:
Thu Aug 26, 2021 12:30 pm
Banksiae seedlings and hybrids are notoriously mildewy. At least the straight seedlings out grow it and achieve the high degree of resistance it demonstrates.
Do they grow out of it without assistance? Or do you intervene?

I get a lot of mildewy seedlings from some things (even things that surprise me like rugosa or blue for you and because it's mentioned in the very first post, I've never had a seedling from Carefree Beauty that isn't mildew ridden to the point they death before reaching 5cm/2inch if no intervention) while others very few (polys...even though the parent/s get powdery mildew). Never quite sure if I should be intervening, I tend to not intervene and generally those that were runty their first year continue to be runty their second year if they survive (one heatwave with 40c+/104f+ temps and most things with noticeable mildew fry to a crisp and don't recover).

On the flip side, after flipping through the new foliage (spring starting in a few days, southern hemisphere), a lot of my earlier rugosa seedlings (2018 sown) that are still around are starting to bud up for the first time (which may be an indicator for a lot of once bloomer types from around that time....like the thorny tangled hell pit of Lord Penzance seedlings down the back...yay but also boo I may need to get in there, I'm going to get stuck on something).

Karl K
Posts: 1417
Joined: Sat Jun 02, 2012 4:49 pm

Re: Taming The wild Ones

Post: # 73260Post Karl K
Fri Aug 27, 2021 1:05 pm

Karl K wrote:
Thu Aug 26, 2021 12:23 pm
... it is useful to remember that maturity in plants begins at the top and moves downward.
I forgot to add that cutting back immature plants will not hasten their maturity.

roseseek
Posts: 5283
Joined: Sun Dec 11, 2011 6:54 pm
Location: Zone 9b Central California, Sunset Zone 15

Re: Taming The wild Ones

Post: # 73261Post roseseek
Fri Aug 27, 2021 2:10 pm

IF you can maintain them until they develop enough root system and foliage mass, they outgrow the mildew issues. That can be a HUGE "if". I've recently obtained potassium bicarbonate which supposedly works well. I haven't used it yet because I used very old Serenade on the Stellata X Minutifolia seedling and burned the daylights out of it. It's putting out more growth and once it appears not to teeter on the edge, I will treat it with the potassium chloride. It's interesting stuff, available from wine and beer making suppliers to reduce acid in brews. A friend steered me to an on line company which had a decent price for a pound but wanted a ton for shipping, so I found one on Amazon who sold it for $8 a pound with free shipping.

I gave up on Carefree Beauty years ago because I refused to spray and it refused to NOT mildew. Not its seedlings as I never raised any. If the parent tightly holds fungal issues to its bossom as a sign of pride, I don't care what its seedlings might do. It's gone. I know CB is "carefree" elsewhere but it never was here. I figure, for the most part, if the seedlings are so diseased they require chemical intervention, perhaps they shouldn't live. But, Stellata mirifica X Minutifolia? No one has ever done that before, at least that I can discover, so I'm treating it when it feels safe. The Banksiae self seedlings have mostly outgrown the mildew, except for the few which didn't and literally died from it. The first batch of Minutifolia selfs all died from it, the one from this batch of seed is (so far and fingers ARE crossed) remaining clean.
Kim
California Central Coast
USDA Zone 9b
Sunset Zone 15
Cooler inland coastal valley with strong marine influence

Karl K
Posts: 1417
Joined: Sat Jun 02, 2012 4:49 pm

Re: Taming The wild Ones

Post: # 73303Post Karl K
Sat Sep 25, 2021 10:54 am

It's a shame when roses that are selected and distributed for their disease resistance eventually become susceptible. 'Carefree Beauty' is one example, 'Tropicana' is another.

There was a report in the ARA sometime in the 1980s that collected reports from around the U.S. on the disease resistance of various popular roses. Among the combined reports for HTs and Floribundas, 'Tropicana' ranked highest. And it was also in the '80s that I learned that 'Tropicana' was susceptible to a specific strain of mildew. Pity!

But it seems likely that 'Tropicana' would still be useful for breeding if another variety could be found with resistance to that special mildew.

Breeders face the same problem with blackspot: "Semeniuk estimates there may be as many as 50 to 100 strains of the blackspot fungus in the United States alone, but he chose seven strains that he had closely studied to test for resistance during his breeding program. The strains, which he maintained in the laboratory, had been cultured from infected leaves from Beltsville, Md.; University Park, Pa.; Ithaca, N.Y.; Tifton, Ga.; Tyler, Texas; Ames, Iowa; and Delaware, Ohio."

Back in the 1930s there was some discussion of "vigor-related" resistance and "true"(i.e. genetic) resistance. 'Golden Bantam' sweet corn, for example, had the vigor to defeat most infections. The genetic resistance was desired by some breeders because it was inherited as a "unit character". Mendelism was all the rage back then. But this type of resistance was often defeated when those pesky microbes mutated themselves.

The answer is not either/or. Vigor is always important, and will reinforce the resistances conferred by specific genes.

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