Double Knock Outâ„¢ (RADtko)

Double Knock Out[sup]TM[/sup] (RADtko) continues to amaze me. Mine gets such minimal BS in my location (only on a small number of the real old or yellowing leaves down the bottom of the bush so far). I consider this performance for my location near-miraculous (for a non-species rose), and I sure hope its fantastic BS disease resistance continues in the many seasons ahead in my location.

For roses in Sydney, this one represents a quantum leap in rose growing.

BUT as a breeder does it also present a quantum leap?

Any feedback here on using it as breeder?

I have no seed using it, yet. Truth be known, I have not used it in earnest either - just a few (casual / not well thought out)dabblings here and there.

Perhaps next season I’ll try harder with it as mom and as dad rose (our spring = September - October - November).

I don’t know that a double sport offers anything different in its genotype than the single form, but there is a lineage of wonderful lines in the family. Carefree Beauty begot KO, which begot Homerun, which is a parent of Jim Sproul’s Thrive, for instance…

That doesn’t necessarily mean that KO would be an easy parent. When a rose is that famous, you can rest assured it is well-milked as a resource for good genes. The fact that excellent progeny exists might speak more to the quantity of attempts than the relative number of successes.

I’m sure others with more experience will weigh-in. As seems to often be the case with really strong parents, I’m not sure that KO allows much diversity in its offspring.

I nonetheless think the answer is a resounding yes.

I think it is a sister and not a sport.

I’m glad to hear that your Dbl KO gets a small number of infected leaves in your difficult blackspot environment. That might indicate that it’s resistance is a horizontal resistance rather than a vertical gene-for-gene resistance. A horizontal resistance will be more durable than vertical resistance. The question is how well it will pass resistance on to it’s offspring.

I have DKO but will be using it for the first time this season. I did order Whimsy which has DKO as the pollen parent. I don’t know anything about Whimsy yet but will be posting my experience with it later this season. I did get a few BS leaves on DKO last season and none on KO. DKO ignored the minimal leaf infection and performed wonderfully. Both set OP hips.

Zlesak did a great presentation that included some information on DKO.

The common blackspot races in the USA are 8,9, and 3. The presentation shows DKO has vertical resistance to race 9 and 3. Also, it has strong horizontal resistance, although The Fairy does best it in horizontal resistance. People in California have noted DKO does get powdery mildew. Overall, very healthy plant but it does have some room for improvement.

As to fertility, it is triploid but does give a lot of pollen which works on various diploids and tetraploids. As mom, being triploid you only get maybe 3-4 seeds per hip. I haven’t worked with it long enough to know about it’s germination rate as female.

Last year I crossed it as a male with Quietness which has vertical resistance to race 8 and 9, and a better looking flower. It gave me a nice seedling, so I am repeating that cross this year to see what else might be in there.

Thanks all.

I think it is a sister and not a sport.

…correct, it has been said by some to share the same parents as KO and not to be a sport of KO.

Any more information about its “breeding behaviors” ? (yes, of course I am very greedy for maximum info LOL).


Double Knock Out is a result of the same cross than Knock Out that Bill Radler repeated the following year. It is indeed a sibling of the original.

Regarding breeding, it worked well as a pollen parent. I kept a Remembrace X DKO last year. I only noted some minor anthracnose. It is barely double, coral red, and dwarf. I specifically chose Remembrance because of its color, dwarfing ability, and general health, so the goal of creating breeding stock for species hybrids succeeded.

I am hoping that the seeds from (Raven x Preference) x DKO germinate soon.

The pollen works. It seems to be really fine, and about moderately picky, but it works well enough to be considered.

Hi Rob,

Whimsy looks interesting. Yes, please keep us posted on it as you get to know it better.

The question is how well it will pass resistance on to it’s offspring.

Hi, jbergeson,

Thank you for raising that, it is totally the pivotal issue of this thread IMHO.

Is there at this point in time, any definite understanding of how horizontal BS disease resistance (such as DKO apparently has) is transmitted?

Is there evidence out there for example, that DKO can trasmit such resistance to its kids? …and how easily???

Hi Charles,

Thanks for confirming DKO’s pollen potency and level of female fertility in your breeding so far. Good luck with the seed germinations (if you have already collected seed from DKO crosses)!!

Hi Michael,

Thanks for the confirmation on DKO pollen potency from your breeding work.

Regarding Whimsy, only City of San Francisco has been repeated used as a seed parent. I know that Teeny Bopper puts out a lot of pollen. It is likely more valuable as a pollen parent, but who knows yet.

My thought was using Whimsy as a pollen parent initially. I’ll post my observations on that one.

It is my understanding that horizontal resistance is a multiple gene type resistance, so it can be strengthened or diluted to varying degrees depending on what you cross it with. David’s slides showed a lot of degrees of variation in hr among cultivars. Single gene resistance on the other hand is a yes/no, it’s either there or it’s not. For horizontal resistance, the seedling’s hr will be somewhere between the two parents. Be careful who you pick for the other parent and the hr will be good.

As to DKO as seed parent, yes I’ve collected seed from her from pollinations I did last Nov. and Dec. (very mild winters here), and the number of seeds is low compared to a ho like Carefree Beauty. DKO is more prolific as pollen donor, but if you have spare pollen she will at least give you some seeds to try.

It is my understanding that horizontal resistance is a multiple gene type resistance, so it can be strengthened or diluted to varying degrees depending on what you cross it with

I am not sure I really “fully get” the genetics of it (no surprise)…

At the bare DNA level, what do scientists actually mean when referring to single gene resistance (~vertical) versus multiple gene (~horizontal) resistance? Are there separate unique genes governing resistance for each of the separate races of black spot?

I am not the most qualified person to answer your questions, but I’m here so I’ll give it a shot.

Single gene resistance means a plant having that gene can block infection completely. Well, at least until the fungus mutates or a different race shows up. Perhaps it changes the shape of the cell pore that the fungus uses to enter the cell so it can no longer physically get into the cell (just a wild guess).

Horizontal blackspot resistance doesn’t prevent infection, but rather limits the growth and reproduction of the fungus.

Hypothetically, let’s say there are 10 horizonal resistance genes. Each one with it’s own way of making life difficult for Mr. Fungus. If The Fairy has 10/10 hr genes and you cross it with Old Blush which let’s say has 6/10 hr genes, on average the resulting seedlings would have about 8/10 horizontal resistance genes. Multiple gene resistance tends to average out between parents. There is a lot of randomness in genetics, but on average you would get 8 of 10 hr genes.

Some plants are completely resistant to one race of bs but not another, so yes vertical resistance genes are race specific. Horizontal resistance stays about the same against several races of bs. So you want vr to prevent the infection in the first place and also hr in case the fungus mutates or a new race blows in on the wind that you don’t have a vr gene for.

In usual conditions vertical resistance needs genes specific to each or a few desease strains. Genes that are not effective against a new strain. When the desease mutates or has many strains breeder working with vertical resistance has to accumulate still more strain specific genes as it is done for many vegetables.

Oppositely, if eventually allowing a little desease, horizontal resistance is against all strains, the known as well as the future ones. This resistance is the result of combined effects of a set of genes that each add a little to the general resistance.

Vertical resistance, being at the moment more effective and easy to introgress or manipulate (gm) is the way of most.

Its constant failure is that it favours the endless new or other desease strains appearance.

Introgress horizontal resistance is not so easy, manipulate allmost impossible so of no use to those intending to patent a gm able gene.

So for black spot infections in roses, I understand then that the genetic mechanism underpinning vertical (race specific) BS resistance, is totally different (i.e. involves different genes) to the genetic mechanism that is responsible for conferring horizontal resistance… right??

Yes, vertical and horizontal resistances are controlled by different genes.

It’s all very interesting, we now have much better information about cultivar resistances so we can make more informed decisions about parents.