Question, disease culling, end of season.

Just a question, with it being the middle of autumn/fall here many seedlings that were good all spring and summer are showing spots. Would you cull?

Simply a question on whether end of season spots are a problem or expected…being in an climate where evergreens are a thing, unsure about these heading into winter dormancy spots.

Hi Plazbo,

At least in the climate I’m in, not worrying so much about end of season spots has been the general attitude of most breeders. If the rose can hold off disease from exploding for most of the season and it builds a bit by fall, that suggests some good horizontal resistance, which is valuable. If the rose can hold things back pretty good until late fall here and looked good most all the summer, it added a lot of value to the garden. Vertical resistance, which is basically all (no disease at all) or nothing (when it is overcome if the rose has low underlying horizontal resistance it looks terrible), seems to be more easily overcome with a new race coming in or a mutation, etc. Horizontal resistance seems to be more predictable year to year for the most part. Maybe for a really long growing season like yours combining as many vertical resistance genes as possible in single roses is the more desirable approach. So, if they have good horizontal resistance that can be a challenge. If they eventually do get spotty by fall, you have a long time of the growing season yet to come that they look bad and would make people unhappy observing them.

If it was me, I’d consider saving the ones that get spotted less fast as others (horizontal resistance) and then try to cross those with roses with different vertical resistance genes to try to combine both types of resistance (plus hopefully beauty, etc.) into your lines.

Thank you. I ditched everything that was spotty earlier in the season, what remains now isn’t particularly bad but is noticeable. I just notice some roses that are deciduous like rugosa, Dagmar Hastrup is spotless, her leaves just yellow and drop, while other rugosa leaves spot and yellow in fall but are fine the rest of the season. So on one hand I know that spotless deciduous leaves are possible but on the other don’t appear to be the standard.

Just trying to wrap my head around practices/preferences from around the world from people who’ve been doing it long enough to know better than myself, see if I could be doing more to prevent future headaches.

Maybe for a really long growing season like yours combining as many vertical resistance genes as possible in single roses is the more desirable approach.

To some extent that’s already happening.

I already use Thornless Multiflora (Rdr1 and Rdr2 due to linkage if I read things correctly) which remains entirely spotless and I don’t have RRD to contend with so that’s a plus. Thornless multiflora will likely be in the lineage of everything I breed in a few generations, just establishing some smaller stature thornless juvenile blooming breeders from it before attempting to bring in other recessives to the primary lines. On a tangent hopefully thornless multiflora will cross with Clinophylla, possibly opens up Bracteata to being more co-operative and then a thornless Bracteata in the f2…curious. I love Bracteata but it’s thorns are a big no.

Sunsprite (Rdr3) is the most saturated least fading yellow here, so is used often for that purpose…Rdr3 isn’t resistant to something here so if Rdr3 is maintained it’ll be accidental, but fingers crossed.

No known source of Rdr4 here at this time, when one becomes available though will be gotten to see how it fares with disease here.

I suspect Eyes For You and Madame Anisette possibly have something, neither spot here but they aren’t fans of the extreme heat. I have a number of MA seedlings which have also remained spotless, possibly is an indicator of some RdrX gene and dominant inheritance.

If they eventually do get spotty by fall, you have a long time of the growing season yet to come that they look bad and would make people unhappy observing them.

11 months of growing season. It’s why I binned Jude The Obscure and never got Julia Child despite it’s praise, both are black bushes in fall here…really unappealing. Jude went so far past spotty, 90%+ of every leaf was just black and didn’t want to drop without some manual assistance. I’m sure it’s a beautiful healthy plant elsewhere but not here in fall.

For what it’s worth, since you mentioned them, both ‘AUSjo’ (Jude the Obscure) and ‘WEKvossutono’ (Julia Child) were spot-riddled nightmares for pretty much the entire growing season in my garden. Of course, not everyone might have my high diversity of black spot strains to work with, but those two were some of the worst performers in terms of disease resistance among all of the roses I’ve grown.

Stefan