Evaluation of Roses from the Earth-Kind

See link below.

Link: hortsci.ashspublications.org/cgi/content/abstract/45/12/1779?etoc

Hi Henry!!

You are fast. I just got the pdf from HortScience today. It was a really fun study to do and I’m excited about what we learned and that the screening methods we used can be useful in screening roses for black spot resistance and get an understanding of what my more likely have durable resistance outdoors. Breeders have selected SOOO heavily for vertical or race specific resistance. It is very interesting and logical that it is the roses with strong underlying horizontal resistance that have endured as the best performing landscape roses over time.

David

It is kind of confusing. Pink Knock Out is a color sport of Knock Out but the resistance is different? Paprika is a bit of an odd shock. It was nastyyyyyy here in Oregon.

Rainbow Knock Out did prove resistant to blackspot but it was absolutely awful in wholesale because it was so easily prone to mildew. It can not be grown into saleable condition in mass with the air circulation loss that comes with growing plants in grow tubes or outdoor row sections. Please keep that in mind when matching it up in breeding.

I wouldn’t be confused about Pink and Knock Out being different resistance wise. Who knows what other mutations accompanied the color change?

I’m not logistically confused, more confused as to what specifically happened between the jump.

Great questions,

Blushing Knock Out has a race specific resistance change compared to the original KO and Pink KO to one of the three races we worked with. We obtained a reversion on Blushing KO to KO in color and isolated it and the reversion like KO was again resistant to the race in question. With Blushing KO reverting relatively frequently, we suggest that perhaps BKO is a periclinal chimera with the color and resistance changes occuring in Layer I of the meristem. When the layers get changed and either Layer II or III overtakes the whole meristem we get the original KO back. This would be great to follow up on. It offers a great research opportunity to study what genetically is different between these two roses to allow for the resistance change.

That is a great point about variable resistances for cultivars based on locality. Additionally, a rose may be great for black spot, but it can get other diseases that limit it. The variable performance based on locality is highlighted in the text and how important horizontal resistance is. We cannot depend on vertical or race specific resistance as there are different races in different places and they are moving and mutating. We would love to have black spot strains collected off from especially roses that showed resistance to all three of the races we trialed to characterize them to see if they are new races and can be added to the international collection. There are at least 11 races in the collection now. We cannot know the underlying horizontal resistance of a cultivar until the race specific resistance is stripped away by an infective race. This study is the first I know of that uses characterized races in a widespread landscape rose cultivar screen to assess both race specific and horizontal resistance. Beginning to use a broader array of races in the collection to strip away the race specific resistances in those resistant to the three we trialed in this study to then see underlying horizontal resistance would be a great next step.

It seems that the best of all worlds is to develop roses that have race specific resistance and then also has strong horizontal resistance once the race specific resistance is stripped away. Knock Out seems to be one of the best in that regard. In the international race array manuscript by Whitaker et al. all 15 or so roses trialed in that paper were infected by at least one race of black spot including Knock Out and Baby Love.

Hopefully this manuscript provides good food for thought and perspective for what tools we have available and which approaches seem reasonable as we breed towards durable black spot resistance in roses.

David

David, great job!

Now to find a supplier for Peachy Cream…